Distribution of vasoactive intestinal polypeptide in the rat heart: effect of guanethidine and capsaicin.
Vasoactive intestinal polypeptide (VIP) is believed to coexist with acetylcholine in postganglionic parasympathetic neurones. However, the presence of VIP in extrinsic nerves and/or other types of intrinsic cardiac neurones has not been excluded. The aim of our study was to examine the distribution and origin of VIP-ergic innervation in the rat heart atria using immunocytochemistry and radioimmunoassay (RIA) combined with two types of denervation: sympathectomy, which was produced by guanethidine treatment and sensory denervation achieved by capsaicin administration. In whole-mount preparations of the intact atria, VIP-immunoreactive (IR) nerve fibres and ganglionic cells were found, the latter being much more numerous in the left atria (LA) than in the right ones. Some of VIP-IR nerve fibres forming bundles appeared to be extrinsic in origin. VIP-IR concentrations determined by RIA in the intact rats were significantly higher in the LA than in the right ones (p < 0.01). However, no changes in VIP-IR levels were found in either atrium after both guanethidine and capsaicin treatment protocols, thus indicating that VIP-immunoreactivity is not associated with either sympathetic or sensory innervation. In conclusion, the ganglionated plexus of the rat atria may comprise at least 3 different neuronal populations expressing VIP-positivity: 1. extrinsic preganglionic parasympathetic fibres, 2. intrinsic postganglionic parasympathetic neurones and 3. intrinsic local circuit neurones that do not express a cholinergic phenotype.
Department of Physiology, Faculty of Medicine, Charles University, Lidická 1, 30166 Plzen, Czech Republic. kuncova@lfp.cuni.cz
Jitka
J
Kuncová
Jana
J
Slavíková
Josef
J
Reischig
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D005725:Ganglia, Autonomic / Q000166:cytology / Q000378:metabolism; D006145:Guanethidine / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000294:innervation; D007150:Immunohistochemistry; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009412:Nerve Fibers / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D013869:Thiolester Hydrolases / Q000032:analysis; D043222:Ubiquitin Thiolesterase; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*
D014660:Vasoactive Intestinal Peptide; D002795:Choline O-Acetyltransferase; D013869:Thiolester Hydrolases; D043222:Ubiquitin Thiolesterase; D002211:Capsaicin; D006145:Guanethidine