N-terminal galanin fragments inhibit the hippocampal release of acetylcholine in vivo.

Using synthetic N-terminal fragments of galanin, galanin (1-7), galanin (1-9), galanin (1-12) and galanin (1-16), we have shown that the minimal sequence required for inhibition of acetylcholine release in vivo from rat ventral hippocampus corresponds to galanin (1-12). The fragment (1-9) displays activity in vivo but only at a very high concentration of 6.23 nmol while galanin (1-7) and C-terminal fragment (17-29) are without effect. Binding studies showed that galanin (1-16) and galanin (1-12) bind with submicromolar IC50 values to rat hippocampal galanin receptors. Galanin (1-9) has substantially lower affinity towards rat ventral hippocampal galanin receptor.