Galanin mediated inhibitory nervous modulation of cutaneous vascular reactions

Noxious stimulation induces local inflammatory responses in a variety of mammals but these reactions are only faint in avian species. The possibility that endogenous galanin inhibits neurogenic vascular responses in avians was tested in the wing skin of anaesthetized pigeons. Intraarterial infusion of nanomolar concentrations of the specific galanin antagonist M35 dose dependently enhanced the small mustard oil induced increase of skin blood flow measured by means of a Laser Doppler Imager. Similarly, the small transient vasodilatation following electrical stimulation of a cutaneous nerve was also enhanced by M35. The effect of M35 was not observed after chronic denervation. Coperfusion of M35 dose dependently augmented the histamine and bradykinin induced plasma extravasation revealed by skin microdialyses, but this effect was abolished in the chronically denervated skin. However, chronic denervation per se enhanced the plasma extravasation induced by histamine but not by bradykinin and this effect was diminished by coperfusion of galanin. The results suggest an inhibitory modulation of cutaneous neurogenic inflammatory reactions by endogenous galanin in the pigeon.