Received September 11, 2005
Revised November 10, 2005
Accepted after revision December 13, 2005
Neuroendocrinology/Endocrinology [270]
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Sex steroids, Serotonin and the Successful Male
Gordon Barrett 1*,
Massimo Bardi 2,
Ana Karina Zavala Guillén 3,
Akio Mori 3,
Keiko Shimizu 3
1 Centre for Cancer Therapeutics
2 University of Richmond
3 Kyoto University Primate Research Institute
* To whom correspondence should be addressed. E-mail: zavalabarrett{at}yahoo.com.ar.
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Abstract |
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The view that androgen action is the primary impetus underlying male-typical behaviour has been irrevocably altered by the profound perturbations in social and sexual behaviour observed in recent models of oestrogen insufficiency in male mice. Evidence is also accumulating for an involvement of oestrogens in the modulation of neural systems that are thought to play important roles in male reproductive functioning. Specifically, the serotonergic system is implicated in diverse autonomic functions, most or all of which are sensitive to oestradiol as well. Although their interaction domains have yet to be examined in male primates, roles have been established for both oestrogen and serotonin in the regulation of male sexual behaviour. We used a blinded, sham treated and self-controlled, randomized, multi-treatment crossover design to test the hypothesis that male sexual behaviour is regulated by oestrogen modulation of the serotonergic system in intact male Japanese macaques. Regression analysis revealed that oestradiol and whole blood tryptophan, but not testosterone nor DHT, had additive, independent effects on male potentia over a range of hormone concentrations, whereas androgens were confirmed to be the primary determinants of sexual motivation. We suggest that modulation of the serotonergic system by 'female hormones' may be fundamental to the regulation of male mating success in higher primates. This might also explain, at least in part, why significant correlations between steroid hormones and male copulatory behaviour have traditionally proven so elusive in this order, thereby warranting a re-evaluation of the current notion that male sexual behaviour has been emancipated from activational hormonal control in higher primates.
Key Words:
Oestrogen, Reproduction, Serotonin
