Galanin: neuromodulatory and direct contractile effects on smooth muscle preparations

Abstract

1 The effects of galanin, a newly isolated neuropeptide, and of a galanin fragment (galanin 1–10) were studied on various smooth muscle preparations in vitro. Direct motor effects as well as effects on electrically induced (neuronally mediated) responses (neuromodulatory effects) were observed. 2 Both gatanin and galanin 1–10 evoked a strong contractile response in rat jejunal longitudinal muscle. This effect was a direct one on the smooth muscle. 3 Addition of galanin to guinea-pig taenia coli inhibited the contractile responses to electrical stimulation, mediated by endogenous substance P and acetylcholine. In the rabbit iris sphincter, galanin reduced the acetylcholine-mediated but not the substance P-mediated contraction evoked by electrical stimulation. The neuromodulatory effects seem to be presynaptic and require the whole or possibly only the C-terminal part of the galanin molecule, since galanin 1–10 was ineffective. 4 Rabbit femoral artery and vein, gastroepiploic and basilar arteries and guinea-pig trachea and main bronchi did not respond to either galanin or galanin 1–10.