Spinal cord injury in rats: inability of nimodipine or anti-neutrophil serum to improve spinal cord blood flow or neurologic status

ABSTRACT— The role of a calcium-mediated increase in vascular resistance and of vascular damage caused by polymorphonuclear leukocytes (PMNLs) in the development of neurologic deficit and disturbance of spinal cord circulation following spinal cord compression was studied in the rat. Spinal cord injury was induced by 5 min of compression with a load of 35 g on a 2.2 × 5.0 mm compression plate. This caused transient paraparesis. The rats received either the calcium receptor antagonist nimodipine or an anti-rat neutrophil serum (ANS). Nimodipine was infused i.v. for 4 h in an amount of 1.5 μg/kg/min starting 60 min after trauma. The number of circulating PMNLs was depleted by intraperitoneal injection of an ANS raised in sheep given 12 h before trauma. This caused a reduction to about 2% of the pre-ANS value. Controls received saline or normal sheep serum. The motor performance was assessed daily on the inclined plane. On day one, the day after injury, the capacity angle had decreased from about 63° preoperatively to close to 32° in the experimental groups. There was then a slow improvement in both the control and experimental groups and on day 4 the capacity angle was close to 43° in all 3 groups. Spinal cord blood flow, as measured with the ^l4C-iodoantipyrine autoradiography method, was similar in all groups on day 4. As neither the neurologic dysfunction nor the spinal cord blood flow was affected by post-trauma treatment with nimodipine or pretreatment with ANS, the possiblity that calcium-mediated vasoconstriction or PMNLs play a role in the development of posttraumatic neurologic disability was not supported by this study.