Dorsal and ventral hippocampal cholinergic systems modulate anxiety in the plus-maze and shock-probe tests.

There is emerging evidence that increased acetylcholine levels in brain reduce anxiety. More specifically there is evidence that some of these anxiolytic effects of acetylcholine are modulated by the hippocampus. In the present study we examined the roles of the cholinergic systems in the dorsal and ventral hippocampus in two animal models of anxiety: the elevated plus-maze and the shock-probe burying tests. We found that microinfusions (10 microg/0.5 microl) of the acetylcholinesterase inhibitor physostigmine in either the dorsal or the ventral hippocampus increased rats' open arm exploration in the plus-maze test, and decreased burying behavior in the shock-probe test. Interestingly, infusions in the ventral, but not the dorsal hippocampus also increased the number of contacts rats made with the shock-probe. Overall, the results suggest that cholinergic stimulation in the dorsal and ventral hippocampus modulate anxiety, but that only the ventral hippocampal cholinergic system is involved in the passive avoidance of painful stimuli. Copyright 2002 Elsevier Science B.V.