Regulation of in vivo whole blood aggregation in rats by calcitonin gene related peptide

The purpose of these experiments was to determine whether calcitonin gene related peptide (CGRP) mediates physiological control of platelet function in vivo. Rat blood pressure was continuously monitored via a femoral arterial cannula, and whole blood aggregation was assessed periodically ex vivo with an impedance aggregometer before and following a 1.4 nmol/kg bolus dose of CGRP_8-37, a specific receptor antagonist of CGRP. Mean arterial blood pressure was not significantly affected by CGRP_8-37 over a 30-min period (p > 0.05). However, whole blood aggregation increased by 38.4 ± 18.0% (p < 0.01) and 32.0 ± 11.2% (p < 0.05), at 5 and 15 min post CGRP_8- 3₇, respectively, when compared with control. Whole blood aggregation was not significantly different from control at 30 min (p > 0.05), suggesting a relatively short duration of action for in vivo CGRP_8-37. These data suggest that CGRP contributes to the maintenance of hemostasis, and that this function may be more important than the better known vasodilatatory effects of this neuropeptide.