Analysis of anatomical sites at which galanin impairs delayed nonmatching to sample in rats.

Galanin, a neuropeptide that coexists with acetylcholine in the septohippocampal pathway of the rat, impairs operant delayed nonmatching to sample (DNMTS) when administered intracerebroventricularly. Microinjection experiments were conducted to determine the anatomical site or sites at which galanin acts to disrupt DNMTS. Galanin (0.1, 0.4, or 1.6 nmol) was microinjected into the ventral hippocampus, amygdala, nucleus basalis magnocellularis, prefrontal cortex, or entorhinal cortex. Galanin disrupted DNMTS in a dose-dependent manner when microinjected into the ventral hippocampus but not at the other sites tested. These findings are consistent with the ability of galanin to inhibit physiological and biochemical actions of acetylcholine in the ventral hippocampus.