Effects of Pregnancy and Female Sex Steroid Hormones on Calcitonin Gene-Related Peptide Content of Mesenteric Artery in Rats1

Calcitonin gene-related peptide (CGRP) levels in plasma and the dorsal root ganglia (DRG) are increased during pregnancy and in ovariectomized rats injected with ovarian hormones. Va-sodilatory responses to CGRP are also increased in these ani-mals. In the present study, we hypothesized that pregnancy and ovarian hormones elevate the contents of CGRP in perivascular nerves. We assessed CGRP-dependent mesenteric vascular re-laxation induced by electrical field stimulation (EFS) and arterial content of CGRP. Because the mesenteric artery represents re-sistance vessels, segments of mesenteric arteries collected from female rats at different stages of the estrous cycle, pregnancy, or postpartum and from male rats were used in this study. The EFS-induced relaxation in the presence and absence of CGRP8–37, an antagonist of CGRP, was used to measure CGRP