Involvement of GABAA receptor sites in diazepam hypothermia.

1. Intraperitoneal (i.p.) injection of diazepam (1.5-6 mg/kg) decreased the core body temperature (BT) of the rats. The effect was dose-dependent. 2. The hypothermia produced by diazepam (6 mg/kg, i.p.) was decreased in animals pretreated with high doses of bicuculline (BIC, 3 mg/kg, i.p.), while low doses of BIC (1.5 mg/kg, i.p.) potentiated the hypothermia. 3. Picrotoxin (PIC, 1 and 2 mg/kg, i.p.) pretreatment also decreased the hypothermic effect of diazepam. 4. Pretreatment of animals with atropine (AT, 10 mg/kg, i.p.) or propranolol (PRO, 10 mg/kg, i.p.) potentiated the hypothermic response of diazepam. Phenoxybenzamine (PHEN, 0.5 mg/kg, i.p.), methergoline (METH, 0.5 mg/kg, i.p.) or pimozide (PIM, 0.5 mg/kg, i.p.) did not change the diazepam hypothermia. 5. Single administration of BIC, PIC, PRO, PIM or METH also induced hypothermia. 6. One can postulate that diazepam hypothermia may be induced through GABAA receptor sites. However, further studies will clarify this hypothesis.