Effect of Chronic Administration of Haloperidol (Intermittently) and Haloperidol-Decanoate (Continuously) on D2 Dopamine and Muscarinic Cholinergic Receptors and on Carbachol-Stimulated Phosphoinositide Hydrolysis in the Rat Striatum
Abstract
Abstract: It has been reported that apomorphine-induced stereotypy is sensitized after a chronic intermittent administration of haloperidol (HPD), but not after a chronic continuous exposure to haloperidol-decanoate (HPD-D). The present study was undertaken to investigate changes in the D2 dopamine and muscarinic receptors in the ratstriatum after the administration of HPD intermittently and HPD-D continuously. The number of striatal [3H] spiperone binding sites increased significantly after HPD-D, but did not change after HPD. Neither the number of [3H](–)QNB binding sites nor carbachol-stimulated phosphoinositide hydrolysis changed after either HPD or HPD-D. These results indicate that the increase in striatal D2 receptors in rats administered HPD-D represents behavioral and biochemical tolerance, and that neither the D2 dopamine receptor supersensitivity nor muscarinic receptor hyposensitivity underlies sensitization of apomorphine-induced stereotypy.
abbreviations used are:
-
- InsP
-
- inositol monophosphate;
-
- InsP2
-
- inositol biphosphate;
-
- InsP3
-
- inositol triphosphate;
-
- HPD
-
- haloperidol;
-
- HPD-D
-
- haloperidol-decanoate;
-
- (-)QNB
-
- (–) quinuclidinyl benzilate;
-
- KD
-
- dissociation constant;
-
- Bmax
-
- maximal number of binding sites.