Synapse-specific interactions between ethanol and opioid receptor-mediated synaptic depression in dorsal striatum

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Project Summary There is no doubt that the alcohol use disorders (AUDs) have a significant socioeconomic toll on the United States and the rest of the world. Many current therapeutics are not sufficiently effective, as they do not target the neurobehavioral underpinnings contributing to the development and maintenance of alcohol abuse in many individuals. There is a critical need for novel therapeutic interventions that can undo the negative effects of ethanol on brain circuitry, restoring cognitive control over drinking behavior. A barrier to progress is a lack of understanding of the specific effects that ethanol has on select synapses within parts of the brain known to control alcohol-related behaviors and even the behavioral role of many of these select synapses in the context of the larger function of each brain region. Our preliminary data indicate that ethanol only affects certain forms of opioid receptor-mediated synaptic plasticity at very specific synapses within the dorsal striatum while leaving plasticity at nearby synapses unaffected. One of these synapses is the inputs from the anterior insular cortex (AIC) to the dorsolateral striatum (DLS). The AIC is involved in ethanol interoception and the DLS controls habitual responding for ethanol drinking and seeking behavior. In vivo ethanol exposure in mice disrupts mu opioid long-term synaptic depression (LTD) at this synapse while leaving mu opioid signaling at other synapses unaffected. LTD mediated by kappa and delta opioid receptors occur at unidentified dorsal striatal synapses and ethanol could have similar differential effects on these forms of LTD. Our data also show that LTD at AIC-DLS synapses is likely mediated by altered cAMP signaling and de novo protein synthesis. The objective of this proposal is to determine synapse-specific opioid LTD mechanisms and how ethanol selectively affects some synapses, while leaving others unaffected and to determine the behavioral relevance of opioid LTD at AIC-DLS synapses. Our central hypothesis is that alcohol disrupts dorsal striatal opioid plasticity at specific synapses due to distinct alcohol-sensitive signaling pathways at synapses that modulate alcohol consumption, seeking, and interoception. In Aim 1, we will identify the impact of in vivo ethanol exposure on mu, delta, and kappa opioid receptor-mediated synaptic depression at specific types of dorsal striatal glutamatergic synapses. In Aim 2 we will determine the mechanisms of ethanol-sensitive and insensitive forms of dorsal striatal opioid plasticity to decipher the impact of ethanol on these signaling pathways. In Aim 3 we will decipher the role of mu opioid LTD at AIC-DLS synapses in ethanol consumption, seeking, and interoception. We will use brain slice electrophysiology, in vitro and in vivo optogenetics, transgenic mice, viral vectors, and pharmacological tools to address these three aims. By understanding the synapse-specific effects of ethanol on plasticity mechanisms at behaviorally-defined synapses in the dorsal striatum, we will identify novel therapeutic targets for treating AUDs. This will be a leap forward towards improving the lives of those that suffer from the effects of AUDs.