Detection of m2 muscarinic acetylcholine receptor mRNA in human corpus cavernosum by in-situ hybridization.

Relaxation and contraction of the smooth muscle of human corpus cavernosum (HCC) of the penis is essential for penile erection and detumescence. Relaxation of the smooth muscle is controlled, locally, by cholinergic, adrenergic and nonadrenergic, noncholinergic neurotransmitters as well as by the vascular endothelium, which lines the lacunar spaces and releases endothelium-derived relaxing factor. Cholinergic neurotransmitters are postulated to act on other neuroeffectors and on the endothelium rather than act directly on the trabecular smooth muscle. We use in-situ hybridization to determine the presence and distribution of muscarinic acetylcholine receptor (mAChR) subtype mRNA in HCC. First, we verified that the riboprobe used for in-situ hybridization is specific for m2 mAChR subtype using Chinese Hamster Ovary cells transfected with m2 mAChR subtype. Then, we validated that the tissue obtained from surgical specimens is adequate for in-situ hybridization. The data demonstrate that m2 mAChR subtype mRNA is expressed in HCC smooth muscle cells. m2 mAChR subtype mRNA expression is not detected in endothelium or nerves. It is possible that this receptor subtype plays a role in smooth muscle contraction.