Vasoconstrictor effects of galanin and distribution of galanin containing fibres in three species of elasmobranch fish

Abstract

Galanin is found in perivascular sympathetic neurons in a wide range of vertebrate species. In placental mammals, galanin has either no effect on blood pressure, or weak depressor effects, but in other vertebrates it has been shown to be a potent pressor agent. To investigate how extensive the vasoconstrictor effects of galanin may be in the vertebrates, the vascular effects of galanin were tested in two species of shark, Heterodontus portusjacksoni, and Hemiscyllium ocellatum, and a ray, Rhinobatos typus. Nerve fibres showing immunoreactivity to galanin were located surrounding gut blood vessels, but were absent from branchial efferent arteries in all three species. Intravenous injection of galanin caused a significant rise in caudal arterial blood pressure in H. portusjacksoni and H. ocellatum, but no change in R. typus. Contraction of segments of pancreatico-mesenteric artery were measured in an organ bath also. Galanin (10 −6 M) caused 21–38% of the maximum K + induced contraction in all species, but no response in efferent branchial arteries from R. typus. In conclusion, in three elasmobranchs, a galanin-like peptide is present in perivascular nerve fibres, and galanin causes differential vasoconstriction in vascular beds. These data extend the number of vertebrate groups in which galanin has been shown to be a vasoconstrictor peptide.