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 degrees C to 32 degrees 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.

5-Hydroxytryptophan↗

PubMed1972

Effect on the rat uterus of the venom from the scorpion Leiurus quinquestriatus.

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Animals↗

PubMed1972

The role of 5-hydroxytryptamine and noradrenaline in the hyperthermic reaction induced by pethidine in rabbits pretreated with pargyline.

1. Inhibition of 5-hydroxytryptamine (5-HT) synthesis by p-chlorphenylalanine protected rabbits pretreated with pargyline from the fatal hyperthermic reaction which occurs on the intravenous injection of pethidine.2. The development of tolerance to morphine did not protect against the fatal pargyline-pethidine hyperpyrexia. Moreover, the injection of nalorphine before or after pethidine conferred no protection.3. Pethidine evoked a hyperpyrexia in rabbits pretreated with lithium sulphate or yohimbine.4. Sodium diethyldithiocarbamate caused a fatal hyperpyrexia in rabbits pretreated with pargyline.5. It is concluded that the pargyline-pethidine hyperthermic interaction might involve the relative concentrations of 5-HT and noradrenaline in the hypothalamus.

Animals↗