Heat production and heat loss in the rat following intracerebral and systemic administration of morphine

Abstract

The fall in core temperature of the rat following either intravenous administration of morphine sulfate or injection of the drug into the anterior hypothalamus is accompanied by a pronounced reduction in oxygen consumption. No significant change in skin blood flow occurred after morphine. The mean rate of fall in temperature in the group of animals injected systematically was greater than that of the animals receiving intracerebral injections. This difference is regarded as an action of morphine apart from the effect of the drug on the thermoregulatory centers. It is concluded that the hypothermic effect of morphine is due to a reduction in metabolic heat production rather than to an increase in heat loss.