Age-Related Decrease of Neurogenic Release of Calcitonin Gene-Related Peptide From Perivascular Nerves in Spontaneously Hypertensive Rats

Changes in the neurogenic release of calcitonin gene-related peptide (CGRP) by perivascular nerve stimulation (PNS) were investigated in perfused mesenteric vascular beds isolated from spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). CGRP-like immunoreactivity (CGRP-LI) in the perfusate was examined by radioimmunoassay (RIA) and identified to be CGRP itself by combined analysis with radioimmunoassay and HPLC. In SHR and WKY preparations, PNS (4 and 8 Hz) evoked a frequency-dependent increase of CGRP-LI in the perfusate, which was abolished by 500 nM tetrodotoxin and the removal of Ca2+ from the medium. In young SHR and WKY (8-week-old), there was no significant difference in the release of CGRP-LI induced by PNS, whereas the release in the 15-week-old SHR was significantly less than in the 15-week-old WKY and in 8-week-old SHR. These results suggest that neural release of CGRP from perivascular nerves in mesenteric resistance vessels of SHR decreases with age.