Role of l-glutamate in systemic AVP-induced hypothermia

It has been reported that systemic injection of arginine vasopressin (AVP) induces a drop in body core temperature (Tc), but little is known about the mechanisms involved. Because glutamate is an important excitatory neurotransmitter involved in a number of thermoregulatory actions, in the present study, we tested the hypothesis that glutamate plays a role in systemic AVP-induced hypothermia. Wistar rats were pretreated intracerebroventricularly (icv) with kynurenic acid, an antagonist ofl-glutamate ionotropic receptors, α-methyl-(4-carboxyphenyl)glycine (MCPG), an antagonist ofl-glutamate metabotropic receptors, or saline 15 min before intravenous injection of AVP (2 μg/kg) or saline. Tc, brown adipose tissue (BAT) temperature, blood pressure, heart rate, and tail skin temperature were measured continuously. Administration of saline icv followed by intravenous AVP caused a significant drop in Tc brought about by a reduction in BAT thermogenesis and an increase in heat loss through the tail. MCPG treatmen...