Effect of changes in baroreceptor input on the intensity of shivering in the anaesthetised cat.

1. Shivering in the barbitone-anaesthetised cat exposed to a lowered ambient temperature was reduced by transient haemorrhagic or drug induced hypotension such that there was a positive correlation between mean arterial blood pressure and the intensity of shivering. 2. Shivering which had been reduced by haemorrhage could be restored by the reinfusion of blood, centripetal stimulation of a buffer nerve or by the intravenous administration of methoxamine. 3. The intensity of shivering was increased by the intravenous injection of methoxamine and by stimulation of a buffer nerve, although the latter response was attenuated by intact buffer nerves. 4. There was a marked variation in the importance of the different buffer nerves in maintaining shivering. 5. Shivering was abolished by deafferentation of the baroreceptors and although it could be restored by electrical stimulation of a buffer nerve methoxamine was then without effect. 6. A prolonged period (90-120 min) of hypotension (50-60 mm Hg) impaired the ability to shiver even after the hypovolaemia and hypotension had been corrected.