Aversion learning in rats and shrews

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My program of research is aimed at understanding the nature of associations that develop between tastes and/or contextual cues and drugs. We evaluate the role of nausea, fear and drug reward in motivating responding to stimuli following pairing with rewarding or aversive drugs. Our work has shed light on the paradoxical finding that in rats a rewarding drug produces avoidance of a taste with which it is paired, but a preference for a context with which it is paired. Although rewarding drugs and drugs that produce nausea both produce taste avoidance in rats, only nauseating drugs produce a conditioned disgust reaction during re-exposure to the taste. This suggests that different mechanisms are involved in taste avoidance produced by emetic drugs and rewarding drugs. Our work is aimed at better understanding this dissociation by evaluating manipulations of the serotonin system (which may produce nausea) and the endocannabinoid system (which may relieve nausea) on conditioned disgust reactions in rats (which do not vomit in response to toxins) and vomiting in shrews. Since the neurobiology of nausea is not well understood, conditioned disgust reactions elicited by a nausea-paired flavor or a nausea-paired context may serve as an effective rodent model to investigate this phenomenon. This work has also led to investigations of evolutionary mechanisms that may guide food selection in rats and shrews; for instance, unlike rats, shrews actually develop a preference for a taste paired with a rewarding drug. Finally, we are also interested in associations that occur between contextual cues and drugs, using a conditioned floor preference paradigm. Our work is aimed at understanding the early phases of opiate dependence, relapse following extinction training and the role of the endocannabinoid system in the extinction of such learning. Our program cuts across the traditional boundaries of psychology, pharmacology and neurobiology, contributing not only to understanding basic processes of learning, but also how those processes impact on food selection, opiate addiction and gastrointestinal malaise. The specific objectives of my research program over the next 5 years include the evaluation of the: 1) Dissociation between conditioned disgust and conditioned avoidance learning, 2) Comparative studies of neophobia, disgust and avoidance in rats and S. murinus, 3) Central regulation of conditioned disgust by endocannabinoids and serotonin, 4) Mechanisms governing the regulation of contextually elicited conditioned disgust reactions, 5) Role of the endocannabinoid system in regulation of the affective properties of naloxone-precipitated morphine withdrawal.