Morphological and functional in vitro and in vivo characterization of the mouse corpus cavernosum

1 In normal mice, the distribution of adrenergic, cholinergic, some peptide rgic, and neuronal nitric oxide synthase (nNOS)-containing nerves were inve stigated. Functional in vitro correlates were obtained. An in viva model wa s developed in which erectile haemodynamics in response to drugs or nerve-s timulation were studied. 2 Immunoreactivities for vesicular acetylcholine transporter protein (VAChT ), nNOS-, and vasoactive intestinal polypeptide (VIP), co-existed in nerve fibres and terminal varicosities. Immunoreactivities for neuropeptide Y (NP Y) and tyrosine hydroxylase (TH) were found in the same nerve structures. 3 Chemical sympathectomy abolished TH- and NPY-IR nerve structures in caver nous smooth muscle bundles. The distribution of calcitonin gene-related pep tide (CGRP)-, nNOS-, VAChT- and VIP-IR nerve structures was unchanged. 4 In endothelial cells of the central and helicine arteries, veins and venu les, intense immunoreactivity for endothelial NOS (eNOS) was observed. No d istinct eNOS-IR cells were found lining the cavernous sinusoids. 5 in vitro, nerve-induced relaxations were verified, and endothelial NO/cyc lic GMP-mediated relaxant responses were established. VIP and CGRP had smal l relaxant effects. A functioning adenylate cyclase/cyclic AMP pathway was confirmed. 6 Neuronal excitatory responses were abolished by prazosin, or forskolin. V IP and CGRP counteracted contractions, whereas NPY and scopolamine enhanced excitatory responses. 7 In vivo, erectile responses were significantly attenuated by L-NAME (50 m g kg(-1)) and facilitated by sildenafil (200 mug kg(-1)). 8 It is concluded that the mouse is a suitable model for studies of erectil e mechanisms in vitro and in vivo.