Cobaltous chloride-induced hypothermia in mice III: effect of pretreatment with 5-hydroxytryptaminergic agents.

The influence of various 5-hydroxytryptaminergic agonist and antagonist drugs on body-temperature response to cobaltous chloride in mice was noted. Pretreatment with p-chloroamphetamine, p-chlorophenylalanine, and p-iodoamphetamine antagonized the body-temperature response to cobalt. p-Chloroamphetamine and p-chlorophenylalanine reduced, while p-iodoamphetamine elevated, brain serotonin levels. The uptake inhibitor agents, fluoxetine and nisoxetine, failed to modify the ability of p-chloroamphetamine to antagonize cobalt hypothermia. Cyproheptadine, methergoline, and xylamidine pretreatment enhanced rather than antagonized body-temperature depression by cobalt. Tryptophan hydroxylase inhibitors antagonized cobalt hypothermia, but receptor-blocking agents were without influence, indicating that antagonism was mediated through mechanisms other than the depletion of serotonin. Elevation rather than depletion of brain serotonin by p-iodoamphetamine and failure of uptake inhibitors to modify p-chloroamphetamine antagonism of cobalt hypothermia lend further support for a nonserotonergic role of these amines in their ability to antagonize body-temperature depression by cobaltous chloride in mice.