Role of 5‐hydroxytryptamine in ketamine‐induced hypothermia in the rat

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Abstract
1 Intraperitoneal injection of graded doses of ketamine produced a dose-dependent fall in body temperature of rats. Similarly, intracerebral injection of much smaller doses produced hypothermia. 2 Pretreatment of the rats with p-chlorophenylalanine (PCPA) greatly attenuated the hypothermic response to ketamine whereas the intraperitoneal injection of 5-hydroxytryptophan in PCPA-treated rats restored the hypothermic effect of ketamine. 3 Depletion of the brain monoamines by reserpine completely prevented the ketamine-induced hypothermia. Treatment with sodium diethyldithiocarbamate (DEDTC), however, did not modify the hypothermic effect of ketamine. 4 Pretreatment of the rats with pargyline potentiated the ketamine-induced hypothermia. 5 Depletion of brain monoamines by reserpine in combination with inhibition of noradrenaline biosynthesis (DEDTC) resulted in a long lasting fall in temperature which was not modified by ketamine. 6 When the ambient temperature was raised from 26° C to 32° C, ketamine-induced hypothermia was much reduced and superimposed on a hyperthermia which occurred in all animals. 7 It is concluded that ketamine produces hypothermia in rats possibly through the release of 5-hydroxytryptamine in the hypothalamus and that this effect is similar in some respects to that produced by morphine in non-tolerant rats.