Activity of the mesolimbic dopamine (DA) system has been implicated both in the pathogenesis of schizophrenia and in the abuse potential of drugs such as amphetamine and cocaine. However, a clear understanding of the role of these DA neurons in behavior has been limited by a relative absence of information regarding the electrophysiological activity of these neurons in behaving animals. It has been postulated that the rewarding effects of cocaine and amphetamine are mediated by elevations in DA synaptic activity at mesolimbic termination sites, particularly in the nucleus accumbens, and that similar elevations in DA activity normally mediate the rewarding effects of natural rewards such as food and water. We will examine the single-unit activity of identified DA neurons in the VTA while cats are consuming substances of varying palatability, and we will determine whether DA unit activity is related to 1) the reward quality of the consumed substance, 2) the motoric requirements of the consummatory behavior, and/or 3) the general arousal level of the animal. We will also examine DA release in the nucleus accumbens during consumption of preferred and non- preferred substances. Finally, we will determine whether reward-related VTA DA cells project to the nucleus accumbens by examining the response of the cells to antidromic activation of the target site.
