Submitted on May 2, 2007
Accepted on August 31, 2007
Selective role of Neuropeptide Y receptor subtype Y2 in the control of gonadotropin secretion in the rat
Leonor Pinilla1, Rafael R Fernandez-Fernandez2, Juan Roa3, Juan Manuel Castellano4, Manuel Tena-Sempere5, and Enrique Aguilar1*
1 Department of Cell Biology, Physiology and Immunology, University of Cordoba, Cordoba, Spain
2 Cell Biology, Physiology and Immunology, University of Cordoba. Faculty of Medicine, Cordoba, Spain
3 Department of Cell Biology, Physiology and Immunology, University of Cordoba, Spain
4 Department of Cell Biology, Physiology and Immunology, University of Cordoba, Cordoba, Spain; Physiology Section, University of Cordoba, Cordoba, Spain
5 Physiology Section, University of Cordoba, Cordoba, Spain; Department of Cell Biology, Physiology and Immunology, University of Cordoba, Spain
* To whom correspondence should be addressed. E-mail: fi1agbee{at}uco.es.
Different signals with key roles in energy homeostasis regulate the reproductive axis. These include neuropeptide Y and polypeptide YY3-36, whose type Y2 receptor is the most abundant of this family in the brain. We evaluated herein the putative roles of Y2 receptors in the control of gonadotropin secretion by means of central administration of PYY13-36 (agonist of Y2 receptors) and BIIE 0246 (antagonist of Y2 receptors) to intact and orchidectomized male rats. In addition, the ability of PYY13-36 to elicit GnRH and gonadotropin secretion in vitro and the impact of fasting on LH responses to PYY13-36 in vivo were also monitored. Central administration of PYY13-36 significantly decreased the circulating levels of both gonadotropins; an effect that was observed in prepubertal and adult rats. Yet, a dual action of Y2 receptors in the control of male gonadotropic axis was evidenced as their activation induced (i) stimulation of gonadotropin responses to GnRH at the pituitary; but (ii) inhibition of GnRH secretion at the hypothalamus. Antagonization of Y2 receptors failed to modify basal LH secretion in intact males, either fed ad libitum or after fasting. In contrast, their central blockade in orchidectomized rats evoked a significant increase in circulating LH and FSH level, suggesting the constitutive activation of Y2 receptor in such stimulated conditions. In sum, our data evidence a complex mode of action of Y2 receptors in the control of gonadotropic axis, with stimulatory and inhibitory actions at different levels of the system that are sensitive to the gonadal status.
