Oxytocin receptor is expressed in the penis and mediates an estrogen-dependent smooth muscle contractility.

Abstract

Oxytocin (OT) is released by the posterior pituitary during male orgasm and is supposed to participate in the ejaculatory process. We now report evidence demonstrating the presence of an OT receptor gene (real-time RT-PCR and Northern blot) and protein (immunohistochemistry, Western blot, and binding studies) expression in the rabbit and human corpus cavernosum (CC) and its possible involvement in postorgasmic penile detumescence. OT receptor is expressed in the penis at a concentration similar to that present in other portions of the male genital tract and mediates CC contractility. OT-induced CC contractility is clearly regulated by the changing sex steroid milieu. In fact, we found that in a rabbit model of hypogonadotropic hypogonadism (induced by a single administration of the long-acting GnRH agonist triptorelin pamoate, 2.9 mg/kg), OT responsiveness was strongly reduced and was completely restored by estradiol valerate (3.3 mg/kg weekly), but not by testosterone enanthate (30 mg/kg weekly). As we found that CC expresses both subtypes of estrogen receptors and P450 aromatase, we hypothesized a physiological role for endogenous estrogens in regulating OT responsiveness. We therefore treated adult rabbits with an aromatase inhibitor (letrozole, 2.5 mg/kg) or an antiestrogen (tamoxifen, 0.25 mg/kg) for 3 wk. Both treatments significantly reduced CC responsiveness to OT stimulation. In conclusion, these findings indicate that OT might participate in inducing postorgasmic penile flaccidity and suggest a new role for estrogens in the male: regulation of CC responsiveness to OT.

• Authors: Linda Vignozzi, Sandra Filippi, Michaela Luconi, Annamaria Morelli, Rosa Mancina, Mirca Marini, Gabriella Barbara Vannelli, Simone Granchi, Claudio Orlando, Stefania Gelmini, Fabrizio Ledda, Gianni Forti, Mario Maggi
• Journal: Endocrinology (Endocrinology) Vol. 145 Issue 4 Pg. 1823-34 (Apr 2004) ISSN: 0013-7227 [Print] United States
• PMID: 14691010 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Aromatase Inhibitors
• Enzyme Inhibitors
• Estrogen Antagonists
• Estrogens
• Nitriles
• Receptors, Oxytocin
• Triazoles
• Triptorelin Pamoate
• Tamoxifen
• Gonadotropin-Releasing Hormone
• Estradiol
• Oxytocin
• Letrozole

Topics

• Animals
• Aromatase Inhibitors
• Enzyme Inhibitors (pharmacology)
• Estradiol (pharmacology)
• Estrogen Antagonists (pharmacology)
• Estrogens (physiology)
• Gonadotropin-Releasing Hormone (agonists)
• Humans
• Hypogonadism (chemically induced, physiopathology)
• In Vitro Techniques
• Letrozole
• Male
• Muscle Contraction (physiology)
• Muscle, Smooth (physiology)
• Nitriles (pharmacology)
• Osmolar Concentration
• Oxytocin (pharmacology)
• Penis (metabolism, physiology)
• Rabbits
• Receptors, Oxytocin (metabolism)
• Tamoxifen (pharmacology)
• Triazoles (pharmacology)
• Triptorelin Pamoate (analogs & derivatives)