Severe impairment of heat-induced saliva-spreading in rats recovered from lateral hypothalamic lesions.

A method has been devised to record saliva-spreading on fur and skin by rats in the heat. Normal males and females increase saliva-spreading with increasing ambient temperatures. Rats recovered from lateral hypothalamic lesions do not spread saliva in the heat, confirming the inference drawn from studies of their drinking behavior that their saliva production is severely impaired. Recovered lateral rats do produce saliva when injected with pilocarpine. The failure to salivate is, therefore, a result of the lateral hypothalamic lesions and is not due to an incompetence of the glands.