Brainstem control of shivering in the cat. I. Inhibition.

Regions containing heat gain tonic inhibitory areas in mesencephalon and upper pons were studied using topical microinjection of a local anesthetic. This inhibition was compared in the mesencephalic decerebrated and intact animals. In mesencephalic animals that failed to shiver, bilateral injections of procaine into the ventromedial pontine tegmental areas released some heat gain responses and in intact anesthetized cats injections in the same regions increased intensity of shivering. These effects on inhibitory areas are reversible and can be repeated in the same preparation several times. Permanent effects were obtained by electrolytic lesions or by the local microinjections of 1% osmic acid. In summary, it is shown, by means of microinjection of local anesthetic, that a tonic inhibitory area located in the ventromedial pontine reticular formation completely inhibits shivering in the mesencephalic decerebrate preparation and partially inhibits shivering in the intact anesthetized preparation.