The Influence of Pregnancy and Gender on Perivascular Innervation of Rat Posterior Cerebral Arteries

The authors investigated the influence of pregnancy and gender on the density of trigeminal and sympa-thetic perivascular nerves in posterior cerebral arteries (PCA) and the reactivity to norepinephrine and cal-citonin gene-related peptide (CGRP). PCAs were isolated from nonpregnant, late-pregnant, postpartum, and male rats, mounted and pressurized on an arteriograph chamber to obtain concentration-response curves to norepinephrine and CGRP. Arteries were immunostained for CGRP-, tyrosine hydroxylase–, and protein gene product 9.5 (PGP 9.5)–containing perivascular nerves, and nerve density was determined morphologically. Pregnancy had a trophic effect on trigeminal perivascular innervation (P <.01 vs male); however, this was not accompanied by a change in reactivity to CGRP. Sympathetic and PGP 9.5 nerve densities were not altered by pregnancy or gender, and there were no differences in reactivity to norepi-nephrine. Together, these results suggest that the increase in trigeminal innervation during pregnancy is more related to nociception than in controlling resting cerebral blood flow. KEY WORDS: Perivascular innervation, pial arteries, pregnancy, rat. sympathetic nerve activity has a protective function dur-ing acute hypertension, where it limits hyperperfusion and decreases blood-brain barrier permeability.5,6 Trigemina