Speaker: Brian A. Baldo, UW Department of Psychiatry
Abstract: Feeding is a simple behavior that is required for the survival of the individual. Fundamentally, feeding replenishes chemical energy and maintains an energy reserve for adaptive behavior and physiological housekeeping functions. Nevertheless, the neural controls over this simple behavior are exceedingly complex. There appear to be specialized brain circuits for distinguishable aspects of feeding, for example, feeding elicited by negative energy balance (hunger/starvation), by the anticipated experience of pleasurable taste (the "dessert stomach"), or by stress ("emotional eating"). My lab explores how these diverse circuits interact, by chemically stimulating discrete brain sites in rats and observing the effects upon the organization of feeding behavior.
Recently, we found that stimulating a specific neurochemical system within the prefrontal cortex, usually viewed as a seat of higher cognition, decision-making, and impulse control, produces a remarkable set of behaviors characterized by intense hyperactivity and abrupt, disorganized feeding responses. The neurochemical system under study was the mu-opioid peptide system (the "brain's own heroin"), known to mediate drug reward and to play a role in drug craving and relapse. Our studies were the first to show that feeding behavior can be driven by stimulating specific opioid-sensitive "hot spots" within the prefrontal cortex. Moreover, we showed that stimulating opioid systems in these cortical hot spots activates simpler downstream brain systems that regulate the homeostatic control of energy balance and body weight. Finally, we have obtained preliminary evidence that opioid stimulation of these same hot spots degrades cognitive function, as measured in a task of working memory.
Taken together, our results indicate that mu-opioid-mediated activation of the prefrontal cortex simultaneously degrades higher cognitive function and elicits dysregulated feeding responses by "usurping" control of lower brain systems that regulate energy balance. Our findings may have implications for understanding eating disorders and addiction, which are characterized by the loss of control over food- or drug-seeking behaviors.