Acetylcholine and its enzymes in some brain areas of the rat under stress.

A period of 1 or 24 h of cold stress (5 degrees C) resulted in a significant decrease of acetylcholine (ACh) concentration in the hypothalamus and hippocampus in rats. In the hippocampus the activity of the choline acetyltransferase (ChAT) was significantly increased after 24 h and that of acetylcholinesterase (AChE) after 1 and 24 h exposure to cold, whereas in the hypothalamus, AChE activity was found to be decreased, albeit only after 24 h exposure. Separate investigation of the dorsal and ventral hippocampus under 24 h of cold revealed that the ACh decreased in the dorsal hippocampus only, where no change in ChAT activity was observed. On the other hand, ACh showed no change in the ventral hippocampus where an increase of ChAT activity was found. Forced swimming for 20 min also induced a significant decrease of ACh in the hippocampus and cerebral cortex, along with a significant increase of choline concentration in the given regions. We conclude that under certain stress situations the cholinergic system in rat brain areas, mainly in the hippocampus and hypothalamus, is activated.