Galanin inhibits acetylcholine release in the ventral hippocampus of the rat: histochemical, autoradiographic, in vivo, and in vitro studies.
A high density of galanin binding sites was found by using 125I-labeled galanin, iodinated by chloramine-T, followed by autoradiography in the ventral, but not in the dorsal, hippocampus of the rat. Lesions of the fimbria and of the septum caused disappearance of a major population of these binding sites, suggesting that a large proportion of them is localized on cholinergic nerve terminals of septal afferents. As a functional correlate to these putative galanin receptor sites, it was shown, both in vivo and in vitro, that galanin, in a concentration-dependent manner, inhibited the evoked release of acetylcholine in the ventral, but not in the dorsal, hippocampus. Intracerebroventricularly applied galanin (10 micrograms/15 microliters) fully inhibited the scopolamine (0.5 mg/kg, s.c.)-stimulated release of acetylcholine in the ventral, but not in the dorsal, hippocampus, as measured by microdialysis technique. In vitro, galanin inhibited the 25 mM K+-evoked release of [3H]acetylcholine from slices of the ventral hippocampus, with an IC50 value of approximately 50 nM. These results are discussed with respect to the colocalization of galanin- and choline acetyltransferase-like immunoreactivity in septal somata projecting to the hippocampus.
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D003864:Depression, Chemical; D019004:Galanin; D006624:Hippocampus / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone / Q000032:analysis*
D010455:Peptides; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone; D019004:Galanin; D000109:Acetylcholine