Central cardiovascular effects of calcitonin gene-related peptide: interaction with noradrenaline in the nucleus tractus solitarius of rats.

The haemodynamic responses to microinjections of rat or human calcitonin gene-related peptide (CGRP) into the nucleus tractus solitarius (NTS) of rats were studied. 40 fmol rCGRP did not significantly modify cardiovascular parameters, but 0.2 pmol decreased blood pressure and heart rate (HR), whereas 2 pmol produced a pressor response with no effect on HR. hCGRP elicited a transient fall in blood pressure when administered at the highest dose (2 pmol), but had no effects when given at 0.2 pmol. A possible functional relationship with catecholamines was also investigated. The hypotensive response to 20 nmol noradrenaline (NA) was significantly modified by simultaneous administration of a low dose (40 fmol, ineffective alone) of rCGRP. When rCGRP (40 fmol) was coinjected simultaneously with an ineffective dose (10 pmol) of NA, a hypotensive response was observed. Our results provide evidence that rCGRP may play a role in the control of cardiovascular homeostasis in the NTS, and suggest a functional interaction between this peptide and NA.