Regional haemodynamic effects of human alpha- and beta-calcitonin gene-related peptide in conscious Wistar rats.

1. A comparative study was carried out to assess the regional haemodynamic effects of intravenous infusion of human alpha- and beta-calcitonin gene-related peptide (CGRP; 0.006, 0.06 and 0.6 nmol h-1) in conscious, unrestrained Wistar rats. 2. With human alpha-CGRP, tachycardia was always accompanied by a fall in mean arterial blood pressure (MBP), but human beta-CGRP at the middle dose caused tachycardia with no significant hypotension. 3. Human alpha- and beta-CGRP both caused dose-dependent falls in MBP accompanied by common carotid and hindquarters vasodilatations and increased flows. The highest dose of alpha- and beta-CGRP caused mesenteric vasoconstriction and renal vasodilatation, but the latter was not associated with an increase in flow. 4. With the intermediate dose, human alpha-CGRP caused more significant haemodynamic changes than did human beta-CGRP. In addition, comparison with previous experiments involving infusion of rat alpha-CGRP indicated that human alpha-CGRP had more potent haemodynamic effects than the former.