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Abstract
The distribution of nerves with vasoactive intestinal peptide (VIP)-like immunoreactivity
has been examined in the heart and vascular system of guinea-pigs. There was a very
sparse supply of fibres to the heart. No immunoreactive cell bodies were found in
the intrinsic cardiac ganglia; however, positive nerve cell bodies were seen along
the superior vena cava near the right atrium. There were immunoreactive fibres with
most arteries; these fibres were located at the media-adventitia junction. The supply
to major distributing arteries, such as the aorta, subclavian, carotid and femoral
arteries as well as to the pulmonary arteries, was sparse. Of the individual vascular
beds, the most densely supplied arteries were the mesenteric and uterine (or in the
male deferential) arteries. Arteries running to other organs or tissues, such as skeletal
muscle, kidney, pancreas, spleen and heart were less densely supplied. There were
clear differences in the innervation of different cerebral vessels. The greatest density
was associated with the anterior and middle cerebral arteries. Fewer nerves accompanied
the posterior cerebral, cerebellar and meningeal arteries. There was a sparse innervation
of the rostral part of the basilar artery. Throughout the body, veins were sparsely
supplied. The distribution of nerves with VIP-like immunoreactivity was not changed
when noradrenergic nerves were degenerated by 6-hydroxydopamine or when substance
P nerves were disrupted by capsaicin. It is concluded that VIP containing nerves innervating
the heart and blood vessels form a population distinct from the substance P-containing
and the noradrenergic nerves. It is suggested that the VIP fibres might be efferent
vasodilator nerves to the blood vessels.