Project Summary/Abstract Methamphetamine (Meth) and alcohol (EtOH) are widely co-abused but little is known about how they interact to cause potential harm. Despite the fact that both drugs have similar effects on peripheral organs, these peripheral effects such as inflammation are typically ignored when evaluating their individual neurobiological effects. Moreover, Meth and EtOH also share common neurochemical underpinnings such as increased crosstalk between glutamate neurotransmission and neuroinflammation that would predict additive or supra- additive neurological effects when the drugs are co-abused. Thus, co-exposure to Meth and EtOH may result in an exacerbated neurotoxic, excitotoxic, and neuroinflammatory profile. No studies however, have systematically examined the co-exposure of Meth and EtOH, their peripheral effects, and the contribution of their combined peripheral effects to an enhanced neurotoxicity. Therefore, the objective of the proposal is to identify convergent peripheral and central neurobiological mechanisms involving defined brain cell types that underlie the potential synergistic neurotoxic effects of the co-exposure to Meth and EtOH. The central hypothesis is that the neurotoxic effects of Meth on dopamine and 5HT terminals and neurons are augmented and preceded by the peripheral pro-inflammatory effects of voluntary EtOH intake on the gut to exacerbate neuroinflammation and excitotoxic glutamate neurotransmission. Specific Aim 1 will determine that inflammation in the gut is associated with voluntary EtOH drinking and will precede and exacerbate the neurotoxic effects of Meth. Specific Aim 2 will define the brain cell phenotype and changes in its transcriptome related to inflammatory mediators and glutamate transmission that are affected by EtOH drinking and subsequent exposure to Meth. The outcomes of Specific Aim 2 will guide and be integrated with Specific Aim 3 that will identify the neural mechanisms, consequences, and neurobiological significance of the co-abuse of Meth and EtOH by assessing how glutamate neurotransmission and the excitotoxicity of Meth are influenced by peripheral inflammation from gut. Moreover, transcription changes derived individually from astrocytes, microglia and neurons identified in Aim 2 in response to peripheral inflammation will be examined for their effects of glutamate neurotransmission. The long-term goal is to highlight the importance of peripheral factors in mediating the neurobiological and behavioral effects of drugs of abuse and to develop a feasible neuroprotective strategy that targets peripheral inflammation and mitigates the harmful biological consequences associated with the co-abuse of Meth and EtOH.