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

1. In normal mice, the distribution of adrenergic, cholinergic, some peptidergic, and neuronal nitric oxide synthase (nNOS)-containing nerves were investigated. Functional in vitro correlates were obtained. An in vivo model was developed in which erectile haemodynamics in response to drugs or nerve-stimulation 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 (NPY) and tyrosine hydroxylase (TH) were found in the same nerve structures. 3. Chemical sympathectomy abolished TH- and NPY-IR nerve structures in cavernous smooth muscle bundles. The distribution of calcitonin gene-related peptide (CGRP)-, nNOS-, VAChT- and VIP-IR nerve structures was unchanged. 4. In endothelial cells of the central and helicine arteries, veins and venules, intense immunoreactivity for endothelial NOS (eNOS) was observed. No distinct eNOS-IR cells were found lining the cavernous sinusoids. 5. In vitro, nerve-induced relaxations were verified, and endothelial NO/cyclic GMP-mediated relaxant responses were established. VIP and CGRP had small relaxant effects. A functioning adenylate cyclase/cyclic AMP pathway was confirmed. 6. Neuronal excitatory responses were abolished by prazosin, or forskolin. VIP and CGRP counteracted contractions, whereas NPY and scopolamine enhanced excitatory responses. 7. In vivo, erectile responses were significantly attenuated by L-NAME (50 mg kg(-1)) and facilitated by sildenafil (200 microg kg(-1)). 8. It is concluded that the mouse is a suitable model for studies of erectile mechanisms in vitro and in vivo.