The protective effects of alpha-melanocyte stimulating hormone on canine brain stem ischemia.

Abstract

To evaluate the influence of alpha-melanocyte stimulating hormone (alpha-MSH), an anti-inflammatory antagonist of the production and action of proinflammatory cytokines, 26 dogs were divided into four groups and exposed to isolated, reversible brain stem ischemia in the presence or absence of alpha-MSH treatment. Brain stem auditory evoked potentials (BAEPs) and regional cerebral blood flow were measured during ischemia and for 5 hours after reperfusion. Group I was composed of five dogs that underwent surgical preparation only. Group II was composed of seven dogs that were exposed to 20 minutes of ischemia without treatment. Group III was comprised of seven dogs exposed to 20 minutes of ischemia with alpha-MSH treatment before and during ischemia. Group IV was composed of seven dogs exposed to 20 minutes of brain stem ischemia with alpha-MSH treatment only during reperfusion. During the ischemic period, BAEPs were abolished in all animals within 10 minutes. With reperfusion, the BAEPs increased to approximately 36% of baseline in Group II dogs that received no treatment. However, this increase was approximately 63% in animals that received alpha-MSH both before and during ischemia (Group III). In Group IV dogs that received alpha-MSH only during reperfusion, BAEPs were increased approximately 10 to 14% more than in Group II during the late reperfusion period. The improved recovery of BAEPs in dogs treated with alpha-MSH suggests that this peptide may have neuroprotective effects in brain stem ischemia and reperfusion injury. This effect may be caused by an antagonistic action of alpha-MSH on cytokine-induced ischemic brain damage.