REGIONAL DIFFERENCE IN THE DISTRIBUTION OF VASOACTIVE INTESTINAL POLYPEPTIDE-IMMUNOREACTIVE NERVE-FIBERS ALONG THE UTERUS AND BETWEEN MYOMETRIAL MUSCLE LAYERS IN THE RAT

To investigate a possible regional variation of the vasoactive intesti nal poly-peptide innervation in the uterus of the cyclic rat, the dist ribution of vasoactive intestinal polypeptide-containing nerve fibres from the cervix to the oviduct end of the uterine horns was studied us ing immunohistochemistry. Immunoreactive nerve fibres were most concen trated in the cervix, where they formed a dense plexus in association with the musculature and surrounding blood vessels, in the uterus, a c lear regional distribution of the vasoactive intestinal polypeptide in nervation was observed. Numerous vascular and non-vascular immunoreact ive nerve fibres were present in the lower part of the uterine hems, w hereas they were sparse in the median region and absent at the oviduct end. Moreover, non-vascular peptide innervation was mostly concentrat ed in the circular layer of the myometrium and also occurred in the en dometrium. Only a very few immunoreactive nerve fibres were present in the longitudinal muscle layer. No change in the peptide innervation p attern was observed during the different stages of the sexual cycle. T he marked regional distribution of the peptide innervation in the rat uterus suggests that the regulatory effects of the peptide occur mainl y in the lower part of the organ and principally affect the circular m uscle layer in the myometrium. (C) 1998 Chapman & Hall.