How does the external environment cause hormonal changes within an individual? How does the brain detect and interpret external cues, integrating them into endocrine physiology? How does bird song cause rapid changes in circulating sex hormones? Why do soccer fans have higher testosterone when their team wins than when it loses?
Despite huge advances in our understanding of biology as a whole, we still know very little about how the brain regulates an animal's constantly fluctuating endocrine status to keep it in tune not only with the physical environment but also the social environment. Of course, we know that the hypothalamus is the key to all changes hormonal. We know that physical stimuli (water, salt balance, pain) can elicit hormonal changes to maintain allostasis, and the pathways involved have been relatively well mapped-out. However, the less tangible stimuli, such as auditory and visual cues, pheromones, temperature and light intensity, have been less well-studied. Our understanding of how these cues are a) detected and b) transduced into hormonal signals is minimal.
Endocrine and behavioral responses to stimuli such as vocalizations have been documented for decades, yet the "black box" approach has been applied to any explanation of the brain's involvement. Any external stimulus has to be first monitored by and then responded to by the brain for the stimulus to have a physiological effect. To affect the reproductive axis, these stimuli must influence the gonadotropin-releasing hormone (GnRH) system. Yet, the focus has been on the end-point of this type of study (i.e., effects upon peripheral hormones and/or behavior). Of course, anthropomorphically speaking, the behavioral endpoint is all that matters as far as the individual involved is concerned: "Do I get my mate" "Did I scare off an intruder?", but how the brain (and the GnRH system) has adapted to effect these responses is rather more important from an evolutionary point of view. This is where my interests lie.
Students and postdocs are encouraged to learn a multitude of molecular, cellular, physiological and surgical techniques to investigate: neuroendocrine control of reproduction and reproductive behaviors; biological rhythms; neuroplasticity in the avian brain; immune function and breeding strategies. These can often be applied in a field situation to get an idea of how complex biological organisms operate in the "real" world.
Ubuka, T., G.E. Bentley, K. Ukena, J.C. Wingfield, and K. Tsutsui. 2005. Melatonin induces the expression of gonadotropin-inhibitory hormone in the avian brain. Proceedings of the National Academy of Sciences (in press).
Osugi, T., K. Ukena, G.E. Bentley, S. O'Brien, I.T. Moore, J.C. Wingfield, and K. Tsutsui. 2004. Gonadotropin-inhibitory hormone in Gambel's white-crowned sparrows: cDNA identification, transcript localization and functional effects in laboratory and field experiments. Journal of Endocrinology 182: 33-42.
Bentley, G.E., I.T. Moore, S.A. Sower, and J.C. Wingfield. 2004. Evidence for a novel gonadotropin-releasing hormone in hypothalamic and forebrain areas in songbirds. Brain, Behavior and Evolution 63: 34-46.
Bentley, G.E. 2003. Melatonin receptor density in Area X of European starlings is correlated with reproductive state and is unaffected by plasma melatonin concentration. General and Comparative Endocrinology 134: 187-192.
Bentley, G.E., N. Perfito, K. Ukena, K. Tsutsui, and J.C. Wingfield. 2003. Gonadotropin-inhibitory peptide in song sparrows (Melospiza melodia) in different reproductive conditions, and in house sparrows (Passer domesticus) relative to chicken-gonadotropin-releasing hormone. Journal of Neuroendocrinology 15: 794-802.
Bentley, G.E. 2001. Unraveling the Enigma: The Role of Melatonin in Seasonal Processes in Birds. Microscopy Research and Technique Special Issue: "The Avian Pineal Gland" 53: 63-71.
Bentley, G.E., J.C. Wingfield, M.L. Morton, and G.F. Ball. 2000. Conspecific and heterospecific male song both have stimulatory effects upon the reproductive axis in female songbirds. Hormones and Behavior 37: 179-189.
Bentley, G.E., T.J. Van't Hof, and G.F. Ball. 1999. Seasonal neuroplasticity in the songbird telencephalon: A role for melatonin. Proceedings of the National Academy of Sciences 96: 4674-4679.
Bentley, G.E., G.E. Demas, R.J. Nelson and G.F. Ball. 1998.Melatonin, immunity and cost of reproductive state in male European starlings. Proceedings of the Royal Society B 265: 1191-1195.