Neuroanatomical Evidence for a Role of Central Melanocortin-4 Receptors and Oxytocin in the Efferent Control of the Rodent Clitoris and Vagina

Authors

  • Helene Gelez PhD,

    Corresponding author
    1. Pelvipharm Laboratories, Orsay parc, Bâtiment Cèdres, ORSAY, France;
      Helene Gelez, PhD, Pelvipharm Laboratories, Orsay parc, Bâtiment Cèdres, 91400 Orsay, France. Tel: +33 (0)164864904; Fax: +33 (0)164864910; E-mail: h.gelez@pelvipharm.com
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  • Sarah Poirier BS,

    1. Pelvipharm Laboratories, Orsay parc, Bâtiment Cèdres, ORSAY, France;
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  • Patricia Facchinetti PhD,

    1. Centre de Psychiatrie et de Neurosciences Broca, Sainte-Anne, Paris, France;
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  • Kelly A. Allers PhD,

    1. Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Disorders, Biberach an der Riss, Germany;
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  • Chris Wayman PhD,

    1. Pfizer Global Research and Development, Discovery Biology (432), Ramsgate Road, Sandwich, Kent, United Kingdom;
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  • Laurent Alexandre PhD,

    1. Pelvipharm Laboratories, Orsay parc, Bâtiment Cèdres, ORSAY, France;
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  • François Giuliano PhD

    1. Pelvipharm Laboratories, Orsay parc, Bâtiment Cèdres, ORSAY, France;
    2. Raymond Poincaré Hospital Neuro-Uro-Andrology, Department of Physical Medicine and Rehabilitation, AP-HP, 92380 Garches, University of Versailles Saint Quentin, Paris, France
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Helene Gelez, PhD, Pelvipharm Laboratories, Orsay parc, Bâtiment Cèdres, 91400 Orsay, France. Tel: +33 (0)164864904; Fax: +33 (0)164864910; E-mail: h.gelez@pelvipharm.com

ABSTRACT

Introduction.  The clitoris and the vagina are the main peripheral anatomical structures involved in physiological changes related to sexual arousal and orgasm. Their efferent control and, more particularly, the neurochemical phenotype of these descending neuronal pathways remain largely uncharacterized.

Aim.  To examine if brain neurons involved in the efferent control of the clitoris and the vagina possess melanocortin-4 receptor (MC4-R) and/or contain oxytocin (OT).

Methods.  Neurons involved in the efferent control of the vagina and clitoris were identified following visualization of pseudorabies virus (PRV) retrograde tracing. PRV was injected into the vagina and clitoris in adult rats in estrous. On the fifth day postinjection, animals were humanely sacrificed, and brains were removed and sectioned, and processed for PRV visualization. The neurochemical phenotype of PRV-positive neurons was identified using double or triple immunocytochemical labeling against PRV, MC4-R, and OT. Double and triple labeling were quantified using confocal laser scanning microscopy.

Main Outcome Measure.  Neuroanatomical brain distribution, number and percentage of double-labeled PRV/MC4-R and PRV-/OT-positive neurons, and triple PRV-/MC4-R-/OT-labeled neurons.

Results.  The majority of PRV immunopositive neurons which also expressed immunoreactivity for MC4-R were located in the paraventricular and arcuate nuclei of the hypothalamus. The majority of PRV positive neurons which were immunoreactive (IR) for OT were located in the paraventricular nucleus (PVN), medial preoptic area (MPOA), and lateral hypothalamus. PRV positive neurons were more likely to be IR for MC4-R than for OT. Scattered triple-labeled PRV/MC4-R/OT neurons were detected in the MPOA and the PVN.

Conclusion.  These data strongly suggest that MC4-R and, to a less extent, OT are involved in the efferent neuronal control of the clitoris and vagina, and consequently facilitate our understanding of how the melanocortinergic pathway regulates female sexual function. Gelez H, Poirier S, Facchinetti P, Allers KA, Wayman C, Alexandre L, and Giuliano F. Neuroanatomical evidence for a role of central melanocortin-4 receptors and oxytocin in the efferent control of the rodent clitoris and vagina. J Sex Med 2010;7:2056–2067.

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