The ability of animals to mount adaptive responses to emotional and physiological stress is mediated by central neural pathways that control neuroendocrine secretion, autonomic function, and motivated behavior. The long-term objective of Dr. Rinaman's research program is to characterize the functional multisynaptic organization of these neural systems. Neuroanatomical, physiological, and behavioral techniques are applied to probe these circuits in rodent species under different metabolic and dietary conditions (e.g., after an overnight fast, or after maintenance on a high-fat diet) that markedly shift homeostatic responses to stress. This research program offers unique opportunities to test hypotheses about brain structure-function relationships. Current projects include a focus on central noradrenergic, glucagon-like peptide 1 (GLP1), and oxytocin-expressing neural signaling pathways.
Ongoing studies in the laboratory analyze stimulus-induced expression of the immediate-early protooncogene c-fos (a marker of neural activation) in rats after exposure to various stress- and anxiety-provoking challenges. Analysis of c-fos expression is combined with retrograde labeling of central neural pathways and immunocytochemical detection of neurotransmitter chemicals to characterize the axonal projections and chemical phenotypes of stimulus-activated cells. These experiments focus on the functional roles played by central noradrenergic and peptidergic neural circuits that link brainstem regions with the hypothalamus and limbic forebrain. Another ongoing project uses live neurotropic viruses for transneuronal tracing of multisynaptic neural circuits that regulate food intake. Other experiments measure changes in hormone secretion and behavior to assess the impact of various physiological and pharmacological stimuli on centrally-mediated stress and anxiety responses.