Sodium nitroprusside-induced hypothermia in mice.

ABSTRACT

The hypothermic response following sublethal doses (1.25, 2.5, and 5 mg/kg) of sodium nitroprusside was investigated in mice. The magnitude and duration of rectal temperature depression were shown to be dose related. Oral administration of nitroprusside (5 mg/kg) failed to alter rectal temperature significantly; subcutaneous, intraperitoneal, intravenous, and intracerebral injections at the same dosage level caused respective drops of 3.61, 3.65, 6.44, and 3.48 degrees. The degree of rectal temperature depression following nitroprusside (5 mg/kg ip) was dependent upon the ambient temperature. The time course of the effect of nitroprusside (5 mg/kg ip) on tail temperature was noted. A transient rise in tail temperature, which coincided with the onset of rectal temperature depression, was attributed to the vasodilatory effect of the drug. Tail temperature depression occurred at the peak and throughout the remainder of the rectal temperature response, suggesting that nitroprusside may decrease heat production. Body temperature depression via intracerebral administration, as well as pronounced sedation following nitroprusside injection, suggests a central component to the thermolytic response.