PROJECT SUMMARY The ventral tegmental area (VTA) is a core component of the neural circuitry that drives goal-directed behaviors and a primary target of drugs of abuse. Although generally regarded as a dopaminergic nucleus, many VTA neurons can signal through release of the neurotransmitters GABA and glutamate. These neurons are also targets of drugs of abuse but much less studied. Like VTA dopamine neurons, activity in VTA GABA and glutamate neurons can profoundly shape motivated behaviors. Furthermore, sub-populations of VTA neurons release more than one of these recycling transmitters, including neurons that co-release dopamine and glutamate, or glutamate and GABA. A major goal of this proposal is to identify how these three major transmitters released from VTA act on postsynaptic neurons to alter behavioral reinforcement. And to assess the contribution of non-dopamine VTA projection neurons and inputs to VTA in opioid-induced behaviors.