Perivascular noradrenergic and peptide-containing nerves show different patterns of changes during development and ageing in the guinea-pig.

The development of noradrenergic and peptide-containing perivascular nerves in common carotid, mesenteric, renal and femoral arteries of the guinea-pig was studied using the glyoxylic acid fluorescence and indirect immunofluorescence techniques on whole-mount stretch preparations at 6 stages between 6 weeks in utero and two years after birth. The noradrenergic plexus was more dense than the peptide-containing nerve plexuses in all the blood vessels, and, in general, calcitonin gene-related peptide-containing nerves were more numerous than substance P-containing nerves which in turn were more numerous than vasoactive intestinal polypeptide-containing nerves. In mesenteric and carotid arteries, noradrenergic nerve density reached a peak at about 4 weeks after birth that was maintained to old age, whereas the peptide-containing vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP) nerve plexuses reached a peak at birth and declined thereafter to about half maximum density in old age. In contrast, in the renal and femoral arteries, peptide-containing nerves reached a maximum density at 4 weeks after birth, while noradrenergic nerve density reached a peak around birth; both noradrenergic and peptide-containing nerve plexuses declined in density in old age. Of the 4 vessels studied, the mesenteric artery showed the greatest density of innervation for both noradrenergic and peptide-containing nerves at all stages of development, while the femoral artery was the least innervated. The possibility that some perivascular peptide-containing nerves play a trophic role during development is discussed.