The mesolimbic regions including the medial and lateral prefrontal cortices, the nucleus accumbens, and ventral tegmental area (VTA) are thought to mediate the neural signals that regulate reward-seeking behaviors. This research program will study the neurophysiology of the influence of ethanol on the reward and learning functions of the mesolimbic system. Advanced methods for simultaneous recording of spike train activity of large scale populations of neurons in different mesolimbic regions over many sessions across days will be applied to obtain information on the circuit functions related to actions of ethanol over different time scales. An initial aim is to determine the progress of changes in the mesolimbic system in rats at all stages of acquisition of self-administration of ethanol by a procedure of fading from a high percent sucrose to a high percent ethanol concentration. Normal Long Evans rats will be compared with the inbred P (ethanol-preferring) rats to be obtained from the Center for Ethanol Research at U. Indiana.
A second aim will characterize change in responses as tone cues are conditioned to provide information about the reward to be obtained at a spout.
A third aim will study neuronal activity in mesolimbic regions on the pattern of operant responses progressive ratio nose poke responding for ethanol in the P rats that exhibit persistent responding during extinction, and enhanced responding during the Alcohol Deprivation Effect. We hypothesize that the nucleus accumbens will reveal the most heterogeneous responses characteristic of central integration; orbital frontal cortex will mediate taste and reward valuation t mediate future behavioral choice selection, medial prefrontal cortex will exhibit neural coding of response selection and that VTA dopamine neurons will track information of cues predictive of future reward. A unifying concept is that ethanol will exert widespread influences by induction of an inflexibility of control over conditioned cue responding for reward seeking behavior.
