Effects of nicotine on plasma corticosterone and brain amines in stressed and unstressed rats.

The administration of nicotine (0.4 mg/kh) to unstressed rats caused a rise in plasma corticosterone which persisted for 60 minutes and a fall in hippocampal 5-hydroxytryptamine (5-HT) at 45 minutes followed by a rise at 60 minutes. In rats which were stressed by being placed on an elevated platform, nicotine caused a reduction in hippocampal 5-HT at 45 and 75 minutes but did notaffect the plasma corticosterone concentration. Rats studied 16 hours after the last injection of a course of treatment with metypone had much reduced levels of plasma corticosterone and hippocampal 5-HT. Under the present conditions metyrapone also much diminished the effects of nicotine on plasma corticosterone levels in unstressed rats but had little effect on the response to stress.