Regulation of cocaine use by astrocyte voltage-gated channels

Project Summary/Abstract Significant effort over the past decades has been devoted to uncovering neuronal mechanisms that regulate substance use, including the use of cocaine. Notable progress in this effort includes evidence that dysregulation of neuronal signaling after cocaine exposure may rely on plasticity within non-neuronal cells. A particularly large share of attention has been paid to astrocytes, fueled by early demonstrations that a variety of brain insults from trauma to neurodevelopmental disorders profoundly alter astrocyte morphology. Cocaine exposure impacts astrocyte cytoskeleton, changing the size and shape of astrocyte cell bodies, processes, and proximity to synapses. Additionally, cocaine triggers changes in the astrocyte ability to initiate and maintain propagation of Ca2+ waves that have established themselves as a prototypical signature of “active” astrocyte signaling. Much less is understood about cocaine effects on astrocyte K+ responses, a key feature of neuroglial interface whereby astrocytes maintain ion homeostasis following neuronal extrusion of K+ ions during action potentials. We provide the first, to our knowledge, evidence that astrocyte voltage-gated K+ channels are affected by and contribute to cocaine use in the rat self-administration model. We present preliminary data that the voltage-gated, KCNQ, channels in astrocytes of the nucleus accumbens shell (NAc) are rapidly and dose-dependently up- regulated by extracellular dopamine, that KCNQ channel activity influences astrocyte Ca2+ responses after cocaine self-administration, and that attenuation of cocaine-seeking by KCNQ inhibition requires functional NAc astrocytes. We propose to use standard pharmacological techniques along with newer molecular approaches, electrophysiology, and Ca2+ imaging to further describe astrocyte KCNQ channel contribution to cocaine use. Our hypothesis is that KCNQ channels regulate astrocyte Ca2+ signaling to impact acquired cocaine-seeking behavior as well as its reinstatement after extinction. Within this hypothesis, we define contribution of neuronal activity, relevance of astrocyte Ca2+ compartmentalization to transmembrane and endoplasmic reticulum domains, and cocaine impact on expression of KCNQ subtypes. We predict that astrocyte KCNQ activity, independent of neuronal KCNQ channels, influences generation of intracellular Ca2+ signals by membrane- proximal sources and that inhibition of astrocyte KCNQ activity pharmacologically or by virus-mediated knock- down attenuates cocaine seeking and cue-induced reinstatement. Results of this experimentation lay the foundation for investigating contribution of astrocyte K+ channels to neuroglial coupling. For example, changes in astrocyte K+ may influence Ca2+ dependent release of neurotransmitter molecules, cytokine production, and secretion of extracellular vesicles or other signals to influence neuronal output and cocaine-associated behavior. Such studies will promote understanding of dynamic roles of astrocytes in the healthy brain and facilitate novel cell-type specific approaches to mitigate cocaine use.