NADPH-DIAPHORASE-CONTAINING, NITRIC-OXIDE SYNTHASE-CONTAINING AND VIP-CONTAINING NERVE STRUCTURES IN THE HEN OVIDUCT - A HISTOCHEMICAL AND IMMUNOHISTOCHEMICAL STUDY

The enzyme NADPH-diaphorase (NADPH-d; a marker of NO producing or nitr ergic neurons) and the neuropeptide VIP have been detected in nerve st ructures of the hen oviduct by histochemical and immunohistochemical t echniques performed on cryostatic sections and whole mount preparation s, In the upper four segments of the oviduct, i.e. the infundibulum, m agnum, isthmus and shell gland, nitrergic and VIP-positive nerve struc tures were particularly numerous in the intermuscular and mucosal laye rs, and were represented by fibres and cell bodies showing mainly a pe rivascular distribution. Functionally, such perivascular structures we re related to the blood dow regulation, Different types of nitrergic p yrenophora were recognized in the walls of the shell gland on the basi s of their peculiar morphology. In the distal zone of the oviduct, the vagina, nitrergic and VIP-positive nerve fibres were widely diffused in the circular muscle, which was particularly thick in this segment. The source of at least a part of such fibres was probably represented by large nerve cell bodies scattered in the layer and containing NO an d VIP colocalized. Functionally these cells retained inhibitory motor neurons causing relaxation of the vaginal smooth muscle.