Antagonism of physostigmine induced hypothermia and neuroendocrine changes following exposure to different environmental temperatures.

1. The magnitude of physostigmine-induced hypothermia increased with decreasing environmental temperature. 2. The hypothermic response was accompanied by significant changes in plasma levels of corticosterone, glucose and fatty acids. 3. Central cholinergic mediation appears to be a significant component of physostigmine-induced hypothermia and neuroendocrine changes at moderate temperature. 4. At lower ambient temperatures cholinergic blockers produced less antagonism of physostigmine-induced effects. 5. The decreased effectiveness of cholinergic blockers at low environmental temperatures and the increased plasma fatty acid levels under almost all conditions studied may be of importance in considering long term therapy with cholinergic agonists.