VASOCONSTRICTOR EFFECTS OF GALANIN AND DISTRIBUTION OF GALANIN CONTAINING FIBERS IN 3 SPECIES OF ELASMOBRANCH FISH

Galanin is found in perivascular sympathetic neurons in a wide range o f vertebrate species. In placental mammals, galanin has either no effe ct on blood pressure, or weak depressor effects, but in other vertebra tes it has been shown to be a potent presser agent. To investigate how extensive the vasoconstrictor effects of galanin may be in the verteb rates, the vascular effects of galanin were tested in two species of s hark, Heterodontus portusjacksoni, and Hemiscyllium ocellatum, and a r ay, Rhinobatos typus. Nerve fibres showing immunoreactivity to galanin were located surrounding gut blood vessels, but were absent from bran chial efferent arteries in all three species. Intravenous injection of galanin caused a significant rise in caudal arterial blood pressure i n H. portusjacksoni and H. ocellatum, but no change in R. typus. Contr action of segments of pancreatico-mesenteric artery were measured in a n organ bath also. Galanin (10(-6) M) caused 21-38% of the maximum Kinduced contraction in all species, but no response in efferent branch ial arteries from R. typus. In conclusion, in three elasmobranchs, a g alanin-like peptide is present in perivascular nerve fibres, and galan in causes differential vasoconstriction in vascular beds. These data e xtend the number of vertebrate groups in which galanin has been shown to be a vasoconstrictor peptide.