Research in my laboratory is focused on identifying and understanding the pathways by which environmental, social and physical stressors are perceived, processed, and transduced into a neuroendocrine response. Several projects are aimed at elucidating the basic neural circuits that mediate stress in fish and focused specifically on the physiological functions of the corticotropin-releasing factor (CRF) system. Another major focus is to investigate the interactions between the stress response and the regulation of appetite and growth in fish. Overall, we use a variety of molecular, endocrine and physiological tools to study the pathways that mediate these interactions. The long-term goal of our research is to provide the basis for the original development of a model on the neuroendocrine pathways that mediate the physiological effects of stress.
Stress and the Neuroendocrine Regulation of Appetite
The regulation of food intake in vertebrates is achieved via a complex brain neuronal circuitry that integrates several stimulatory and inhibitory signals of central and peripheral origin. Members of the corticotropin-releasing factor (CRF) family of neuropeptides, on the other hand, are generally recognized as critical brain mediators of the stress response. Although our studies show that CRF and the related peptide urotensin I (UI) have potent appetite-suppressing effects in fish, we do not know the nature of the interactions between the neuronal pathways involved in mediating the stress response and those involved in the control of appetite. Therefore, a major thrust of our research is to determine to what extent the CRF- and UI-synthesizing neurons of the brain mediate the appetite-suppressing effects of known environmental stressors such as hypoxia, ammonia toxicity, and the transition from fresh to saltwater. Using a combination of molecular, pharmacological, and microscopy techniques, we are also investigating the neuroanatomical targets of the CRF- and UI-synthesizing neurons within the hypothalamic feeding center.
The Caudal Neurosecretory System as a Mediator of the Stress Response
In fish, in addition to the potential role of brain CRF-related peptides in mediating the appetite-suppressing effects of stress, peripheral CRF and UI may also be involved in the regulation of food intake and growth. The caudal neurosecretory system (CNSS), a unique neuroendocrine structure found in the tail of fish, has high levels of CRF and UI gene expression. Therefore, we are currently undertaking a series of experiments to determine whether peripheral CRF and UI are mediators of the stress response and to assess the potential roles of circulating CRF-related peptides in gastrointestinal physiology.