I (Mary Jeanne Kreek, MD) was asked by several friends and colleagues to write an autobiographical and scientific article for this issue featuring Women in Neuroscience. I have elected to invite the three other female neuroscientists in my Laboratory, The Laboratory of the Biology of Addictive Diseases at The Rockefeller University, to join me, first, with a brief autobiographical sketch and then with a brief summary of their most recent scientific research. These are our stories.

In 1964, I became part of a new team headed by Prof Vincent P. Dole at the Rockefeller Institute for Medical Research that included the late Dr Marie Nyswander, a practicing psychiatrist working in addiction treatment. I was a resident in internal medicine at New York Hospital/Cornell Medical Center at the time. Within 6 months, between January and July, we performed all of the basic clinical research leading to the FDA approval and national, and then international implementation of, the first pharmacological treatment of opioid addiction, methadone maintenance treatment. My 55-year career in neuroscience has remained focused on specific aspects of the neurobiology, genetics, and development of specific treatments of specific addictive diseases. Our laboratory work continues with a high level of scientific activity and communications thereof.

When I joined Prof Dole's laboratory, I was the only female scientist in the group. The other women were assistants for research, other types of technical support and parts of our administrative staff. At that time the word professor was not used but rather “Members,” each of whom was Head of a separate Laboratory. No Rockefeller laboratory had a woman as a head of laboratory. At that time there were two outstanding women scientists, Dr Rebecca Lancefield, whose name was recognized by all physicians since we had all learned the Lancefield strain of streptococcal disease, not knowing that Lancefield was a woman. The other was Dr Gertrude Perlmann, an outstanding biophysicist who made many contributions to our fundamental understanding of biology.

In 1964, I was told by the Professor and Head of Laboratory to whom I had been recruited to collaborate on the initial studies of developing a potential effective treatment for opiate addiction to put on a white dress, that women working in laboratories, both technicians and nurses, only wore white dresses. I said no, I would not wear a white dress, I would wear clothes with a brown lab coat in the laboratory that would come off when I went to lunch the same as it was done by the male scientists and I would put on a white lab coat when I went to the hospital in-patient unit. I was also told that I could not go to the faculty dining room, that that was for men only. To visit the original, you had to walk up a brief flight of stairs to what has, in recent years, been part of the library. I was to go a flight below into what is now called Welch Hall, which, because of gaps in memory, many say was the original faculty dining room. It was not. Downstairs was the so-called women's dining room where nurses and Research Assistants had lunch, which was very elegantly served in a beautiful room. I said no, I would not go downstairs for lunch, I am a scientist (becoming faulty in 1967 as an Assistant Professor).

I have been a scientist and specifically, a neuroscientist, at the Rockefeller University since my fellowship experience from January to July 1964 and then full-time on the Faculty since July 1967.

My interests in pursuing a career in both medicine and science began very early. I started competing in the Science Fairs in public schools in Washington, DC at age 12 and did this yearly until age 17 when I went to college. During the last 2 years of high school I was selected to be the Washington, DC representative at the National Science Fair. When I was 16, I took the competitive exams for the Westinghouse Science Talent Search (STS) and, based on the exams plus my project description, was selected to be a “Top Forty” contestant to be brought to Washington, DC (although DC was my home I stayed at the hotel with the other 39 students). I was ultimately selected to be in the top 10 and thereby received significant college scholarship funds. Two of the many scientists who interrogated me at the final Westinghouse competition were Dr I. I. Rabi, a remarkable physics Professor at Columbia University and Dr Detlov Bronk, who, initially, was a Professor of Biophysics at Johns Hopkins University. Dr Bronk was the Head of the Rockefeller Institute for Medical Research when I first arrived in January 1964. I remembered him well, of course, but astonishingly, he also remembered me and my STS science project from 1954.

I would probably have elected to go to college at Yale, Harvard, or Columbia, but they accepted no women into their universities at that time (although Harvard and Columbia had female affiliate colleges, Radcliffe and Barnard). I applied to, and was accepted at, MIT, the college of my father and brother, but chose not to go there because at that time there were very few (less than 25) women undergraduates at a largely male-dominated university. I elected to go to Wellesley College. This turned out to be an excellent choice since they had an extremely strong Chemistry Department as well as a very good Zoology Department (botany was a separate department). Before my senior year, I was selected to do 1 year of research work, to write a thesis and compete for the highest of all honors at graduation, the Durant Scholar Award. For this research work I was provided with my own laboratory, a separate, small room, which I shared with a graduate student (master's degree candidate; Wellesley did not grant the PhD degree). I was urged to do a thesis that would span chemistry and biology. I was introduced by the chair of the Chemistry Department to a professor at the University of Connecticut who had very recently created yellow carnations by plant hybridization techniques. The professor wanted to know what chemical made yellow carnations yellow. The chemicals that make red carnations red and pink carnations pink had recently been defined. It was an extremely challenging project that took me frequently to the laboratories at MIT and occasionally elsewhere. However, by early spring of 1958, I had defined that 2′,4,4′ trihydroxy chalcone was the chemical making yellow carnations yellow.

After graduation, I decided to go directly to medical school and incorporate scientific research in my medical work in some way. At that time medical schools took very few women. I applied to five medical schools: Harvard, Yale, Johns Hopkins, Cornell, and Columbia. I was accepted at each. I elected to go to Columbia University College of Physicians and Surgeons (“P and S”). In my class of 120 entering first-year students, seven were women. We started with seven and we ended with seven but only three of us survived the entire 4 years (the other four transferred elsewhere). I found the first year of medical school extremely boring, all memorization, and I went to see the Dean after 3 months. He understood and arranged for me to interact frequently with a scientific journal club and the clinical rounds of the division of neuroendocrinology and endocrinology. Also, I was allowed to spend 6 months in basic research during my last year.

My earlier research experience had included the opportunity to spend two summers in basic chemistry research at the National Bureau of Standards (at age 17 and 18) and every summer thereafter, from age 19 to 22 after my first year of medical school (final free summer) at the National Institutes of Health, in the National Heart Institute working directly under the endocrinologist, Dr Frederic C. Bartter, best known for discovery and elucidation of the role of aldosterone, and defining “Bartter's syndrome.”

Despite the fact I had done very well in medical school and probably would have been selected by the mandatory computer match to go to one of the top hospitals for my internship and residency (e.g., Massachusetts General Hospital, Brigham Hospital or Columbia Presbyterian Hospital), none of these three hospitals at that time took women as house staff. The same Dean who arranged for me to be able to do research throughout my medical school years urged me to apply to Cornell University New York Hospital since he knew that they would take one woman every 1 to 3 years. I applied to two other academic centers known to take an occasional woman. I did my entire house staff at NY Hospital Cornell from 1962 to 1967.

The most important event to impact my career in science and neuroscience came in the autumn of 1963 when a Professor from Rockefeller, Vincent P. Dole, MD, known for his work in hypertension, lipid metabolism, and obesity, with the permission of the Chairman of Medicine at Cornell, came and spoke to the entire house staff. He wanted two young physicians to join him. He was planning to change his entire laboratory to the studies of addictive diseases and specifically to attempt to develop a medication to treat heroin addiction, a problem that was expanding very rapidly in the New York City area and much of the United States. Every member of the house staff asked to be interviewed. Professor Dole graciously interviewed all 40 plus of us and selected two candidates. Prof Hugh Luckey, Chairman of Medicine, stated that he could not afford to lose two house staff physicians for 6 months since in this pre-“Bell Commission” epoch, most physicians in training were working 80 or more hours per week.

I crossed 68th street into the side gate of Rockefeller in early 1964. I returned to NY hospital in July 1964 but continued to participate in the research that I had begun at Rockefeller, which was to determine the long-term safety, physiological effects of and effectiveness of methadone maintenance treatment for opiate addiction. Professor Dole and a second physician, Dr Marie Nyswander, a psychiatrist practicing in New York City, who was also recruited to come to the university in the winter of 1964, and I had conducted this research at the in-patient unit of the Rockefeller Hospital where methadone was shown to be extremely effective, although in a very small number of very long-term heroin addicts. Our research was reported by Dr Dole at the “Old Turks” (AAP) meeting in May 1966. The first research paper “Narcotic Blockade” (Dole, Nyswander, & Kreek, 1966b) was published very soon thereafter in the Archives of Internal Medicine as well as the transcription of the AAP meeting (Dole, Nyswander, & Kreek, 1966a).

Eventually Professor Dole turned all the clinical studies and the more fundamental studies of the neurobiology of opiate addiction over to me and, by 1974, turned his research interests to the field of alcoholism, a field in which he spent the rest of his career. In 1973, the FDA approved the IND for long-term use of moderate- to high-dose methadone maintenance put together with the pro bono help of Eli Lilly, who immediately after approval turned the medication over to the public domain.

In 1974 Prof Dole was seriously contemplating leaving the University and leaving research, although he later stayed in research and turned his entire laboratory to study alcoholism I did not wish to leave because my research was going extremely well. Rockefeller did not have such a thing (then or now) as independent Assistant Professors (my rank at the time). Dr Dole thus appealed to the then President, Dr Frederick Seitz, and after I was interviewed by Dr Seitz, he decided I could “spend two or three more years” alone on my own project, not in anyone else's laboratory at Rockefeller. I am eternally grateful for this decision, one that was to apply only if I could raise all the money for my salary and my research and if I would move my laboratory to an independent site in a different building. I have, in fact, stayed for 45 years since that decision in 1975.

My pathway within the University is semantically torturous, but in fact, I simply worked alone, led my own research group, brought in all my own funding, including my own salary from late 1974 until March 1994, when I became the second woman to become a full Professor at Rockefeller University (the first being Mary Beth Hatten, still very active in her research). Mary Beth Hatten and I owe this change in policy to one of our earlier presidents, the Nobel Prize Laureate, Dr Torsten Wiesel. Torsten came to my laboratory to see me in early 1992, 2 months after he became President and suggested that women should become full Professors at Rockefeller.

In summary, my work on the neurobiological basis of specific addictive diseases, opiate, cocaine, and other stimulant addictions, alcoholism, and most recently cannabis addiction, continues with a wonderful team of 18 scientists and diverse support staff for primarily bench based research, but also basic human clinical and genetics research, all here at the Rockefeller University and Rockefeller Hospital. The Laboratory, which started in 1975, is the Laboratory of the Biology of Addictive Diseases.

My name is Yong Zhang. I was asked by my mentor, Dr Mary Jeanne Kreek, to contribute to the Women in Neuroscience special issue and I graciously accepted because the reason I am a scientist today is largely attributed to first, my parents, but also the teachers and mentors whom I have encountered along the way.

When I was very young, both of my parents were sent to the rural areas of Hainan Island for “re-education” during the Culture Revolution in China. I was often left in kindergartens for months. Fortunately, when I was about 5 years old, I had an opportunity to live with my parents, where my mother served as a local “barefoot doctor,” meaning folk healer. My mother was a pathologist and graduated from a prestigious medical school in China. Being a “barefoot doctor” in the countryside gave her the opportunity to not only treat patients in the “re-educated” group but also peasants from the nearby villages who needed medical attention. In those days, my mother was busy helping the locals day and night, from treating flu to providing expert care during labor and delivery (my mother was trained as a midwife in a nursing school when she was a young girl). Witnessing what my mother did, I realized that being a doctor was helpful for others.

My curiosity to become a scientist started early. When I was in middle school, students often spent time working in farms growing rice and vegetables. I became curious about growing plants and remember watching vegetables growing and wondering how different seeds with similar looks could generate different plants. I frequently asked one of my teachers questions related to plants. He told me to become a scientist when I grew up. In those days there were no universities open to the public in China. Most high school students went to the countryside after graduation. Fortunately, by the time I was ready to graduate high school, all universities were open to the public. Amazingly, any high school student could enter university to continue their education if they passed the university entrance exams and were accepted by the universities in China.

After I graduated from high school, I studied medicine at Hainan Medical School primarily under the influence of my mother. Our class had 80 students and only nine of them were women. The first year of medical school was very competitive and relatively dry. However, I enjoyed Physiology class because we got a chance to do experiments in the laboratory. I did my best in Pathology to make my mother proud. Physiology describes processes or mechanisms operating within an organism under normal condition, whereas Pathology describes the abnormal or disease condition. I was interested in how physiological conditions became pathological, and how it can be reversed by medicine when I was studying pathophysiology.

When I was doing rotation in hospitals as an intern, I interacted with patients with all kinds of illnesses. It was a great feeling to see how patients recovered with the help of medical treatments. However, it happened frequently that we were not able to treat patients with cancers and other severe diseases. We could only help to reduce symptoms since it was impossible to treat the causes of many diseases. There was only limited information on prevention and treatment. My curiosity in science deepened greatly because I realized that there was no cure for so many diseases. Upon graduation from medical school I began working in the first affiliated hospital of Medical School of Shantou University for a few years as an anesthesiologist. This is when I decided to come to the United States to continue my studies.

I was fortunate to be accepted to the PhD Program in the Biology Department at Hunter College of City University of New York. Transitioning into a PhD student was not easy at the beginning. First, because English is not my native language, I had to work hard to master the new language. Second, as a PhD student, we were required to teach undergraduate students in biology classes. It took me a while to have everything under control. I immediately realized there was a dramatic difference between a medical and PhD student. A PhD student needs to research extensively about his/her projects all the time. A medical student needs to have a sharp memory.

At Hunter, I chose to work in the laboratory of Professor Jesus Angulo. Dr Angulo introduced me to the field of drugs of addiction research. I was interested in how drugs of abuse could change the structure and function of the human brain which can eventually lead to addiction. The drug we focused on was methamphetamine (METH). METH is a highly addictive psychostimulant that can easily cause addiction. This is mainly caused by the release of large amounts of dopamine and this extremely high release can cause changes in the brain.

To study the effects of METH on the brain, adult rats were repeatedly injected with METH, simulating abuse of METH in humans. We then examined the rat brains that had been exposed to METH at different time points after METH injections. We focused on the mesolimbic and striatonigral dopamine pathways where the major dopamine neurons in the brain are located. We found changes in the abundance of the messenger RNA (mRNA) encoding the enzyme tyrosine hydroxylase and preprocholecystokinin in the substantia nigra zona compacta and the ventral tegmental area using in situ hybridization histochemistry. We also found increases in the expression levels of striatal and accumbal preprotachykinin mRNA in responses to repeated METH injections, suggesting that METH exposure led to neurobiological changes in the brain. I was the first PhD student to graduate from Dr Angulo's laboratory.

I was very impressed by several female professors in the Biology Department when I was at Hunter. They not only taught classes for graduate and undergraduate students, but also ran active laboratories at the same time. They were my role models and shaped me into the person I am today. Beginning with my mother's guidance and training, I have been extremely fortunate in my life and career to be nurtured and instructed by exceptional women scientists and doctors. This, in part, is what led me to my current position. After receiving my PhD in 1999, I joined Dr Mary Jeanne Kreek's laboratory at the Rockefeller University where I am currently Research Assistant Professor.

Abuse of prescription opioid analgesics such as oxycodone has been a major health problem in the United States. Over the past 10 years, my research has focused on examining the behavioral and neurobiological consequences of oxycodone self-administration in a mouse model. In our first study published in 2009, we characterized self-administration of oxycodone in adolescent and adult male C57BL/6J mice and examined how this affected striatal dopamine levels (Zhang et al., 2009). In 2014, we used an extended self-administration paradigm to examine oxycodone self-administration in adult C57BL/6J mice and its effect on selective striatal neurotransmitter receptor mRNA expression (Zhang et al., 2014). Subsequently, we also compared gene expression changes in several brain regions of the adolescent and adult mice following 14-day oxycodone self-administration (Zhang, Brownstein, et al., 2015). In 2017, we used RNA sequencing to study how oxycodone self-administration would change transcriptome in the dorsal and ventral striatum in adult C57BL/6J mice (Zhang et al., 2017). We found that adolescent and adult mice differed in oxycodone self-administration, suggesting differential sensitivity to the reinforcing and neurobiological effects of oxycodone in the younger mice. We also found that adolescent and adult mice showed significant difference in gene expression in various brain regions including dorsal stratum, hippocampus, and hypothalamus following chronic oxycodone self-administration.

In summary, repeated oxycodone exposure altered the brains and facilitated the development of vulnerability to opioid addiction upon subsequent re-exposure. I will continue to design and develop new studies which could shed light on the mechanism underlying drugs of abuse in the future under the mentorship of and collaboration with the other exceptional women scientists who have contributed to this article.

My name is Kyle Allyson Windisch. For the last 5 years, I have spent innumerable hours and countless weekends training in Dr Kreek's laboratory as a postdoctoral fellow expanding on my preclinical behavioral neuroscience. Despite the metaphorical (and occasionally actual) blood, sweat, toil, and tears during this time, I still love being at the bench. My curiosity for science began very early. My grandfather was recruited as a young professor at the University of Michigan to assist in the establishment of the Wyoming State Veterinarian Laboratory. His passion for science and compassion for all living things sparked my curiosity for knowledge and science at a very young age. Originally keen on following in his footsteps, my focus shifted from veterinary medicine to neuroscience in high school following my primer to the black box of the mind in an introductory psychology course. As an undergraduate at Indiana University Bloomington, I triple majored in psychology, biology, and chemistry and spent nearly 2 years in the laboratory of Julie Stout, assisting in research on human basal ganglia disorders.

Following graduation, I was still unsure of which path to take (i.e., pursuing a pure MD or MD/PhD) and opted to do a “short” post-bac in a research laboratory to help gain clarity on this momentous decision. I serendipitously was hired as a research technician in the laboratory of Dr Sean O’Connor at the Indiana University School of Medicine. Dr O’Connor specialized in examining the electrophysiological effect of ethanol administered intravenously to reduce between-subject PK/PD variability in brain ethanol exposure and nonpharmacological effects (e.g., taste and smell). Although thoughtfully incredulous at first, Sean incrementally gave me autonomy in the laboratory such that by the end of my 5-year tenure he had conferred on me the auspicious title of “technical maven”. For Sean, my growing technical proficiency, curiosity, and tenacity to find the correct solution not my gender was what mattered. It was here that my passion for understanding and unraveling, at least in part, the puzzle of addiction was ignited. As I would routinely find myself in laboratory until the wee hours of the morning unaware that hours, not minutes, had passed as I wrote code to make sense of the brain “squiggles” on the screen, I realized that academia, not medicine, was my true passion.

This revelation resulted in a pivot from medicine to graduate school. I completed my graduate work at Indiana University-Purdue University Indianapolis (IUPUI) in the Psychology Department Neuroscience of Addiction program under the phenomenal mentorship of Dr Cristine Czachowski with my thesis entitled “Role of Group II metabotropic Glutamate Receptor Subtype 2 (MGLUR2) in Appetitive and Consummatory Aspects of Ethanol Reinforcement.” Through a series of opportune events my path led to a postdoctoral fellowship in the laboratory of Dr Mary Jeanne Kreek at the Rockefeller University. Over my last 5 years in Dr Kreek's laboratory, I have extended and deepened my knowledge and research in the field of addiction neuroscience. As Dr Kreek has extended the opportunity to remain in the laboratory as a Research Associate scientist, I am excited to continue and extend my research here with new scientific collaborations and research directions. As well, beyond my scientific development, Dr Kreek has encouraged me (both tacitly and overtly) to mentor the next generation of scientists be it summer high school students, graduate students, or the research assistants/technicians. It is through this mentoring that I hope to pass on two things. First, as a LGBTQ + woman in STEM from a conservative part of the country, I want to be the role model that I did not have growing up. Second, I want to pass on the preeminent life lesson of my training, succinctly put by Sean in a recent email, “if I have given anything to you…, I hope it is that part of your value systems puts friendship (and collegiality) ahead of profit.”

My research spans the gambit of addiction from alcohol to opiates, psychostimulants, and cannabinoids as well as from in vitro, preclinical rodent, and humans. Clinically, we have examined factors that influence the subjective effects of ethanol. Our studies (Kosobud et al., 2015) revealed that recent moderate drinkers had increased subjective perceptions of intoxication during the ascending breath alcohol concentration (BrAC) slope of a computer-controlled IV (intravenous) ethanol exposure, while light drinkers had increased feelings of intoxication during the descending slope. Similarly, we found that higher recent drinking was associated with lower acute tolerance to the positive stimulating effects of alcohol during a 3-hr IV alcohol “clamp” (i.e., BrAC maintained 60 mg/dl). Together, these findings suggest that moderate drinkers may be at risk for increased alcohol consumption due to their sensitivity to the intoxicating subjective effects of alcohol during the ascending phase and protracted positive subjective effects of alcohol.

Beyond examining the subjective effects of ethanol, for several decades Dr O’Connor strove to elucidate viable clinical markers for early detection of alcohol use disorder (AUD). Despite the utility of the event-related potential (ERP) P3 component in identifying endophenotypes of AUD, susceptibility of P3 to practice and/or fatigue effects limits use for detecting acute or adaptive effects of alcohol exposure. Using an adaptive stop signal task (aSST) a reliable STOP P3 component insensitive to repeated testing during and across sessions was observed (Plawecki et al., 2018). STOP P3 latency and amplitude were differentially affected by exposure to 60 mg/dl alcohol clamp depending on response strategy utilized by the subject (FAST vs. SLOW). Overall, the findings suggest the potential utility of the aSST in the detection of endophenotypes of AUD risk.

Drs O’Connor, Li, and Ramchandani pioneered establishing IV ethanol administration in humans. IV self-administration allows for the precise control of drug exposure, standardized dosing across subjects, and limits the confounding “non-pharmacological” aspects associated with traditional oral consumption models. IV ethanol self-administration has been successfully implemented in mice, monkeys, and humans. However, a method by which nondeprived rats will reliably self-administer pharmacologically relevant quantities of ethanol intravenously remains elusive. With my initial graduate projects I attempted to develop a functional method by which nonfood or water-deprived rats would reliably self-administer ethanol intravenously with responding driven by the reinforcing properties of ethanol (Windisch, Kosobud, & Czachowski, 2014). I was able to establish stable operant responding in nondeprived rats using a reinforcer complex of an oral sucrose solution plus IV ethanol. Further examination using a multiple schedule design demonstrated that the oral component of the reinforcer complex, not the IV ethanol, was driving the operant responding. Therefore, despite the numerous novel approaches used (e.g., increased ethanol concentration, warmed infusate, use of rat line selectively bred for high oral alcohol consumption, compound reinforcer, and sucrose fade), the method could not overcome the aversive properties of IV ethanol administration in the rat.

My dissertation work transitioned from IV models to neural modulatory systems relevant to drug addiction (Windisch & Czachowski, 2018). Using the sipper tube model, which procedurally separates the seeking response (lever pressing) from the consummatory response (drinking), we demonstrated that systemic orthosteric, but not allosteric, agonist activation of metabotropic glutamate receptor subtype II (mGluR2/3) significantly reduced ethanol seeking with no effect on ethanol consumption. We further found that agonist doses that did not reduce initial locomotor activity significantly reduced sucrose seeking, consumption, and body weight. Overall, the findings suggest that mGluR2/3, particularly in nucleus accumbens core, are involved in reinforcer seeking.

During my postdoctoral fellowship, in collaboration with senior scientist and phenomenal surgeon Dr Yong Zhang, I expanded my research into opiates investigating the effect of adolescent oxycodone self-administration (Zhang et al., 2016). Adolescence represents a critical window of neural development with significant remodeling and maturational refinements. Few studies have examined the consequences of adolescent oxycodone exposure on persistent neurobiological and behavioral effects in adulthood. Our studies reveal that adolescent, but not adult, oxycodone self-administration results in increased oxycodone-induced conditioned place preference and sensitization to the locomotor effects of oxycodone. As well, adolescent, but not adult, oxycodone self-administration results in a significant reduction in oxycodone-induced antinociception. Overall, we found that adolescent oxycodone exposure results in increased subjective reward for oxycodone with reduced analgesic effect suggesting that adolescent exposure may increase potential for oxycodone addiction during adulthood.

Unlike opioid addiction, for which methadone, buprenorphine-naloxone, and, to a lesser extent, extended release naltrexone are available treatment options, currently no pharmacotherapeutic is approved for the treatment of psychostimulant use disorder. Preclinical and clinical studies suggest that the mu opioid receptor (MOR) antagonist/kappa opioid receptor (KOR) partial agonist naltrexone (NTX) is moderately effective in reducing the subjective effects and self-administration of cocaine. However, no preclinical studies have examined the abilities of the structurally similar MOR antagonist/KOR partial agonist nalmefene (NMF) in blocking cocaine reward/reinforcement. We demonstrated that both NTX and NMF block cocaine place preference, but neither block cocaine-induced hyperlocomotion (Windisch, Reed, & Kreek, 2018). This suggests that both NTX and NMF may be viable pharmacotherapeutics for treating some aspects of cocaine use disorder.

Despite the recent push in legalizing cannabis, little is known regarding the potential developmental and neuroanatomical changes that occur following cannabis exposure. Recent collaborative research with Dr Teri Milner has shown that acute THC exposure results in sex-dependent changes in the hippocampal opioid system (Windisch et al., 2019). These changes suggest that THC exposure differentially alters the hippocampal opioid system priming it for increased opiate associated learning and vulnerability for opioid misuse.

My name is Amy Dunn, and I have recently completed my Ph.D. here with Dr Kreek (October 2019) at the Rockefeller University. While academic science has a long way to go toward diversity and inclusivity, I feel incredibly lucky to have had the chance to learn from so many inspiring women during my time as a student. As a freshman at the University of Pittsburgh, I joined Dr Nancy Kaufmann's laboratory to study aquaporin biology. I worked in the laboratory throughout my undergraduate career and earned degrees in molecular biology and urban studies. During the summer of 2012, I participated in the Summer Undergraduate Research Fellowship (SURF) program at Rockefeller in Dr Brian Chait's laboratory. I worked with a postdoc mentor to learn more advanced biochemistry techniques and optimized a protocol for a novel mass-spectrometry method that the laboratory was developing. I loved Rockefeller, for the science as well as the community, and returned in 2014 to start my PhD.

I had no previous neuroscience or pharmacology background, but I was immediately interested in the Kreek laboratory after I heard Dr Kreek speak at a first-year graduate student class. I was particularly excited about the structure of the laboratory, which combines preclinical and clinical research for a uniquely translational approach, and I was inspired by all of the work that the laboratory had done over the years to tangibly improve the lives of people with addictive diseases. After rotating through several diverse laboratories during my first year of graduate school, I ultimately decided to join the Kreek laboratory for these reasons, as well as the incredible mentors in the laboratory, including Drs Yong Zhang and Kyle Windisch.

Over the past years, I have learned an immeasurable amount from my fellow laboratory members about how to be a good scientist, and also a good laboratory citizen. I have really appreciated how endlessly supportive, insightful and patient my mentors have been—particularly Dr Windisch and a senior research scientist Dr Brian Reed—as well as the opportunity to have so many fantastic women to look up to as role models in the laboratory. Additionally, I have had the chance to mentor younger scientists, both in the laboratory and through outreach programs at Rockefeller like the Summer Neuroscience Program for high school students. This kind of collegiate and friendly culture had such a positive impact on my PhD experience, and I hope to find it—and perpetuate it—in my postdoc and beyond. In January 2020, I started my postdoctoral research at the University of Pennsylvania with Dr Julie Blendy, a long-time collaborator of the laboratory. In fact, Dr Yong Zhang's essential work demonstrating the effect of the A118G variant of the MOR on opioid self-administration (Zhang, Picetti, et al., 2015) was done using the mouse line created by Dr Blendy (Mague & Blendy, 2010).

Throughout the course of my PhD, my work in the Kreek laboratory has focused on the pharmacology and behavioral effects of KOR agonists. The opioid system mediates mood and reward and is comprised of three G protein-coupled receptors (GPCRs) and their endogenous peptide ligands. Activation of the KOR, by its endogenous peptides, the dynorphins and by exogenous agonists, has been shown to block the rewarding effects of drugs of abuse in animal models. KOR agonists, therefore, have been investigated as potential therapeutics for addictive diseases. Unfortunately, in human studies, KOR agonists cause negative side effects such as sedation, aversion, and psychotomimetic effects like hallucinations.

Several strategies are currently being employed to develop KOR agonists that block the rewarding effects of drugs of abuse with fewer side effects, including the development of KOR agonists with unique pharmacology. When activated, GPCRs like the KOR signal through G proteins as well as other signaling pathways, such as β-arrestin-2. Recent studies have shown that these downstream signaling pathways can be differentially activated by agonists, called “biased” agonists, potentially leading to differential downstream behavioral effects in animal models (Luttrell, Maudsley, & Bohn, 2015; Mores, Cummins, Cassell, & van Rijn, 2019). In two studies published in 2018 and 2019, we examined both the G protein and β-arrestin-2 signaling properties of a large set of structurally diverse KOR agonists (Dunn, Reed, Erazo, Ben-Ezra, & Kreek, 2019). We found that β-arrestin-2 signaling, but not G-protein signaling, correlated with the effects of the compounds in a mouse model of KOR-mediated sedation. This suggests that KOR agonists that are “G-protein biased,” meaning they signal more through G protein than β-arrestin-2 pathways, may cause less sedative side effects than “unbiased” KOR agonists. We hope that this can inform future KOR-targeting drug discovery efforts.

Additionally, we have been examining the effects of the unique KOR agonist nalfurafine in a variety of behavioral mouse models. Approved in 2009 in Japan to treat pruritus, nalfurafine is the only selective KOR agonist that is currently in use in humans. Despite its well-documented, robust activation of KOR signaling pathways, it does not appear to cause KOR-mediated side effects like aversion or hallucinations at the therapeutic dose in humans (Kozono, Yoshitani, & Nakano, 2018). We tested varying doses of nalfurafine in mouse models of the blockade of cocaine reward, as well as mouse models of aversion and sedation. We found that at low doses, nalfurafine modulated cocaine reward without causing apparent sedation or aversion. Interestingly, we found that low doses of another KOR agonist had a similar effect, suggesting that the modulation of drug reward might be particularly sensitive to KOR.

The hypothesis that very little KOR activation is needed to block drug reward, and that this might be beneficial to avoiding the negative side effects of KOR activation is consistent with the idea first suggested in the late 1990s that a KOR partial agonist may be useful for treating addictive diseases (Kreek, 1997). Unfortunately, there are currently no selective KOR partial agonists available to test. To this end, the laboratory has been engaged in a drug discovery project over the past 5 years. Through grants and collaborations with both the Robertson Foundation and the Tri-Institutional Therapeutics Discovery Institute, we have received over 400 unique chemical compounds to screen. For each compound, we are testing binding to the KOR, as well as G protein and β-arrestin-2 signaling activation in order to identify a selective KOR partial agonist. Together, we hope that these projects will contribute to the development of KOR agonists as safe and effective treatments for addictive diseases.

Over the past 54 years of my laboratory's independent existence, the Laboratory of the Biology of Addictive Diseases, we have been very generously funded by public and private sources. I personally held a K05 Senior Career Scientist Award for 25 years. Our laboratory, in collaboration with laboratories at Cornell New York Hospital, held an NIH-NIDA P60 Center Grant Award for 26 years. We continue to have diverse NIH grants as well as diverse grants from the private sector both large and small. With my scientists I have published over 400 original, scientific research papers and over 150 concept and hypothesis papers and reviews. At this time there are 18 members of my laboratory and our research is divided into three major domains. We continue to study the molecular neurobiology of the impact of opiates, including heroin and oxycodone, cocaine, alcohol, and marijuana in rat and mouse models. We developed and continue to utilize the 10- to 18-hr extended access self-administration model in rats. Diverse techniques including quantitative solution hybridization protection assays developed by my laboratory and more recently RNA-seq are used to measure gene expression and gene variants in our specific inbred strains of rodents accompanied by studies in direct analysis of DNA. We also, for the past 5 years, have directed a major effort to attempt to develop an effective medication for the treatment of cocaine addiction and for alcoholism, funded by multiple competitive grants. We have designed, with the help of outside chemists, and had made for us, primarily in China, over 400 novel compounds, most of which are directed at the KOR, which we have hypothesized and shown to be counter modulatory for the effects of the MOR.

In addition, we have basic clinical research ongoing, utilizing the Rockefeller University Hospital in-patient and outpatient units. We are examining alterations, primarily in the specific neuroendocrine systems. Since 1996, we have rigorously ascertained numerous volunteer research subjects including healthy volunteers and persons with opiate addiction, cocaine addiction, alcoholism or some combination thereof and, most recently, also cannabis addiction. In addition to rigorous diverse instrument ascertainment of each individual, and after obtaining all essential informed consents, we have conducted genetic studies to determine which gene variants may be associated with which specific addictive diseases. Over 200 gene variants of different genes have been identified as significantly associated with and, thus contributed to, the vulnerability to develop specific addictive diseases. Many of these findings have been replicated by different populations ascertained by our group in collaboration with scientists in Sweden, the Netherlands, and Israel. Others have been replicated by independent scientific groups in different populations.

Overall, since our initial studies in 1964, my laboratory and the wonderful scientists in my laboratory, including many men as well as the three women who have contributed to this chapter, have worked in very effective teams to conduct studies on specific addictive diseases and the potential treatments thereof.

CONFLICT OF INTEREST

Authors report no conflict of interests.

AUTHOR CONTRIBUTIONS

All the authors provided critical feedback and approved the final manuscript. Conceptualization, M.J.K.; Writing-Original Draft, M.J.K., Y.Z., K.A.W., A.D.; Writing-Review & Editing, M.J.K., Y.Z., K.A.W., A.D.