VASOACTIVE-INTESTINAL-PEPTIDE IN THE HAMSTER SEMINAL-VESICLE - DISTRIBUTION, BINDING-SITES AND POSSIBLE FUNCTIONS

The presence and functional role of vasoactive intestinal peptide in t he hamster seminal vesicle were studied by a combination of structural and functional approaches. The use of an immunofluorescence staining technique in both cryostat sections and whole-mount preparations revea led that vasoactive intestinal peptide-immunoreactive nerve fibres wer e mainly localized in the lamina propria of the mucosal layer. In doub le-stained preparations, vasoactive intestinal peptide immunoreactivit y was found to be localized in nerves also containing acetylcholineste rase activity. At the ultrastructural level, the use of an immunogold staining method showed that vasoactive intestinal peptide immunoreacti vity occurred in large granular vesicles (80-150 nm in diameter) in ne rve varicosities which also contained small pleomorphic agranular vesi cles. In order to evaluate the anatomical distribution of vasoactive i ntestinal peptide binding sites in the seminal vesicle, we have utiliz ed an in vitro receptor autoradiographic technique. Vasoactive intesti nal peptide binding sites were localized in the basal region of the se cretory epithelium, in the muscle layer and in the wail of blood vesse ls. In vitro incorporation of [H-3]L-leucine into protein by tissue sl ices revealed that vasoactive intestinal peptide (1 mu M) significantl y increases the amount of released protein. Vasoactive intestinal pept ide (0.1-1 mu M) did not affect the resting tension of the muscle but significantly inhibited the increase in muscle tension induced by carb achol. Atropine prevented the effect of carbachol, indicating that the latter is mediated by muscarinic receptors. Our results suggest that in the hamster seminal vesicle, vasoactive intestinal peptide is invol ved in the modulation of muscarinic function and in the control of sec retion.