The involvement of brain serotonin in the clonidine-induced hypothermia in rats.

The effects of manipulation with brain serotonergic (5HT) activity on clonidine-induced hypothermia in rats were investigated. Lesion to the median raphe nucleus as well as p-chlorophenylalanine pretreatment significantly potentiated the temperature decrease after 0.2 mg/kg of clonidine. Pretreatment with a 5HT releasing agent--fenfluramine, or a 5HT receptor agonist--m-chlorophenylpiperazine (mCPP) antagonized the effect of clonidine. Additionally, both fenfluramine and mCPP given alone produced an elevation in body temperature. These results are discussed in terms of an involvement of the 5HT neuronal system in clonidine hypothermia, and the dissociation of the role of 5HT system in clonidine-induced behavioral and vegetative effects is suggested.