Galanin attenuates the effects of scopolamine but not exposure to a novel environment on acetylcholine release in the rat ventral hippocampus

In vivo microdialysis was used to measure the effects of galanin on extracellular acetylcholine concentrations in the ventral hippocampus of rats produced by exposure to a novel environment or scopolamine. The novel environment produced a significant increase in acetylcholine release, to 58% above baseline. This effect was insensitive to pretreatment with galanin (5 mu g, i.c.v.) or the peptidergic galanin receptor antagonist M40 (16 mu g, i.c.v.). In contrast, galanin strongly attenuated the increase in acetylcholine release produced by scopolamine (0.3 mg/kg, s.c.). These results indicate that galanin differentially affects the increases in acetylcholine neurotransmission produced by a pharmacological and an environmental stimulus.