Galanin: neuromodulatory and direct contractile effects on smooth muscle preparations

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. 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. Addition of galanin to guinea-pig taenia coli inhibited the contractile response 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. 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.