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Open Access Highly Accessed Research article

Estrous cycle influences the expression of neuronal nitric oxide synthase in the hypothalamus and limbic system of female mice

Monica Sica1, Mariangela Martini1, Carla Viglietti-Panzica12 and GianCarlo Panzica12*

Author Affiliations

1 University of Torino, Department of Anatomy, Pharmacology and Forensic Medicine, Neuroscience Institute of Turin (NIT), Laboratory of Neuroendocrinology, , C.so M. D'Azeglio 52, 10126 Torino, Italy

2 National Institute of Neuroscience-Italy (INN), Torino, Italy

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BMC Neuroscience 2009, 10:78  doi:10.1186/1471-2202-10-78

Published: 15 July 2009

Abstract

Background

Nitric oxide plays an important role in the regulation of male and female sexual behavior in rodents, and the expression of the nitric oxide synthase (NOS) is influenced by testosterone in the male rat, and by estrogens in the female. We have here quantitatively investigated the distribution of nNOS immunoreactive (ir) neurons in the limbic hypothalamic region of intact female mice sacrificed during different phases of estrous cycle.

Results

Changes were observed in the medial preoptic area (MPA) (significantly higher number in estrus) and in the arcuate nucleus (Arc) (significantly higher number in proestrus). In the ventrolateral part of the ventromedial nucleus (VMHvl) and in the bed nucleus of the stria terminalis (BST) no significant changes have been observed. In addition, by comparing males and females, we observed a stable sex dimorphism (males have a higher number of nNOS-ir cells in comparison to almost all the different phases of the estrous cycle) in the VMHvl and in the BST (when considering only the less intensely stained elements). In the MPA and in the Arc sex differences were detected only comparing some phases of the cycle.

Conclusion

These data demonstrate that, in mice, the expression of nNOS in some hypothalamic regions involved in the control of reproduction and characterized by a large number of estrogen receptors is under the control of gonadal hormones and may vary according to the rapid variations of hormonal levels that take place during the estrous cycle.