Role of the Prelimbic Cortex and Rostromedial Tegmental Nucleus in Aversion Learning and Compulsive Drug Use

Medical University Of South Carolina, Charleston SC

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Abstract

? DESCRIPTION (provided by applicant): Continued drug use in spite of the negative consequences associated with abuse of illicit substances is a key feature of addiction. This continued reward seeking in the face of punishment, or punishment resistance is observed in both humans and animals exposed to drugs of abuse, but its underlying mechanisms are largely unknown. Ongoing work in our lab suggests a major role for the recently identified rostromedial tegmental nucleus (RMTg), which is activated by aversive stimuli and reward omission, and inhibited by rewarding stimuli. Moreover, the RMTg sends a prominent inhibitory projection to midbrain dopamine (DA) neurons, and stimulation of the RMTg reduces activity of DA neurons in the ventral tegmental area (VTA). My preliminary data also implicates the prelimbic region (PL) of the prefrontal cortex in punishment resistance, a notable finding given the existence of monosynaptic connections from the PL to the RMTg. Hence, we hypothesize that a functional circuit mediating punishment resistance exists between these structures. The role of PL efferents to the RMTg in punishment resistance has yet to be characterized, however, and the precise way in which PL neurons may affect neural activity in the RMTg remains unknown. Accordingly, Aim 1 will first attempt to extend our preliminary findings to determine the ways in which temporally- and spatially-restricted inhibition of PL activity produces punishment resistance in responding for food, and then we will assess whether these same parameters are capable of modulating cocaine self-administration under punishment. Aim 2 will serve as a valuable complement to the previous aim by assessing whether inhibition of the PL modulates the expression of reward-prediction errors in the RMTg. Together, these aims will help to clarify a major gap in our understanding of the broader neurocircuitry that mediates punishment resistance and maladaptive reward seeking, and how the RMTg integrates diverse signals in the brain to encode aversion.