Effects of α-MSH on kainic acid induced changes in core temperature in rats

Abstract

The effects of intraperitoneal (i.p.) administration of kainic acid (KA) and α-melanocyte-stimulating hormone (α-MSH) alone or in combination, on core temperature of freely moving rats were examined. KA or saline was administered once (10 mg/kg) and α-MSH or saline was given repeatedly i.e. 10 min before and 10, 30 and 60 min after the administration of saline or KA. Two doses of α-MSH were used: 0.5 and 2.5 mg/kg. KA alone produced a biphasic effect on core temperature, i.e. an initial short-lasting hypothermia followed by hyperthermia that lasted about 6 h. The higher dose of α-MSH had a potentiating effect on KA-induced hypothermia, while the lower dose of α-MSH increased the hyperthermia produced by KA. α-MSH administered alone produced a late (3 h), dose-dependent increase in core temperature. It is conceivable that repeated administration of α-MSH in the doses used in our study may cause a cumulative effect in raising body temperature for a limited period of time. The previously described interactions between KA and α-MSH, respectively, with dopaminergic and serotoninergic systems may account for the effects on core temperature in rats observed in our study.