GABAA and GABAB receptor sites involvement in rat thermoregulation.

1. Intraperitoneal (i.p.) injection of muscimol (MUS, 2-8 mg kg-1) decreased the core body temperature (BT) of the rats dose-dependently. 2. Intracerebroventricular (i.c.v.) injection of MUS (1 microgram/microliter/rat) also caused a fall in BT. 3. The hypothermia induced by MUS was inhibited by pretreatment of the animals with either bicuculline (BIC) or picrotoxin (PIC). 4. i.p. Injection of baclofen (BAC, 2.5-10 mg kg-1) induced hypothermia. Higher dose of the drug (20 mg kg-1) caused an initial fall followed by a marked increase in BT. 5. i.c.v. Injection of BAC produced a rise in BT. 6. The hypothermic effect of BAC was antagonized in animals pretreated with either BIC or PIC, while hyperthermic effect of the drug was potentiated with PIC pretreatment. 7. i.c.v. Injection of isoguvacine (ISO) induced hypothermia, which was attenuated in rats pretreated with either BIC or PIC. 8. It can be concluded that: activation of GABAA or GABAB receptor sites respectively may induce hypothermia or hyperthermia in rats.