Effect of age on vascular content of calcitonin gene-related peptide and mesenteric vasodilator nerve activity in the rat.

Effects of age on sensory nerve vasodilator activity and vascular calcitonin gene-related peptide (CGRP) levels were investigated in Fischer 344 rats, aged 6, 20 and 27 months. Increases in pressure to transmural nerve stimulation (TNS) of the isolated perfused mesentery were greater at 27 months compared to 6 or 20 at frequencies of 4 and 8 Hz. With guanethidine to block adrenergic nerves and methoxamine to increase smooth muscle tone, TNS-induced vasodilation of the perfused mesentery decreased with age, reaching statistical significance at a frequency of 4 Hz and 27 months. There were no significant differences with age in concentration-response curves to CGRP in the perfused mesentery, except for the oldest rats at low concentrations of CGRP which showed increased vasodilation. Levels of CGRP-like immunoreactivity (CGRP-LI) in mesenteric and femoral arteries at 27 months were significantly less compared with 6 and 20 months; in the renal artery CGRP-LI was significantly decreased by 20 months. This study suggests that decreased sensory nerve function in aging animals may contribute to age-related alterations in circulatory hemodynamics.