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 /sup 125/I-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 fully inhibited the scopolamine stimulated release of acetylcholine in the ventral, but not in the dorsal, hippocampus, as measured by the microdialysis technique. In vitro, galanin inhibited the 25 mM K/sup +/-evoked release of (/sup 3/H)acetylcholine from slices of the ventral hippocampus, with an IC/sub 50/ value of approx. = 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.
- Research Organization:
- Istituto di Ricerche Farmacologiche Mario Negri, Milano (Italy)
- OSTI ID:
- 6938571
- Journal Information:
- Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 84:20
- Country of Publication:
- United States
- Language:
- English
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550601* - Medicine- Unsealed Radionuclides in Diagnostics