Gq-DREADD Selectively Initiates Glial Glutamate Release and Inhibits Cue-induced Cocaine Seeking

Abstract

Background Glial cells of the central nervous system directly influence neuronal activity by releasing neuroactive small molecules, including glutamate. Long-lasting cocaine-induced reductions in extracellular glutamate in the nucleus accumbens core (NAcore) affect synaptic plasticity responsible for relapse vulnerability. Methods We transduced NAcore astrocytes with an AAV viral vector expressing hM3Dq (Gq) DREADD under control of the glial fibrillary acidic protein (GFAP) promoter in 62 male Sprague Dawley rats, 4 dnSNARE mice and 4 wild type littermates. Using glutamate biosensors we measured NAcore glutamate levels following intracranial or systemic administration of clozapine-N-oxide (CNO), and tested the ability of systemic CNO to inhibit reinstated cocaine or sucrose seeking following self-administration (SA) and extinction training. Results Administration of CNO in GFAP-Gq-DREADD transfected animals increased NAcore extracellular glutamate levels in vivo. The glial origin of released glutamate was validated by an absence of CNO-mediated release in mice expressing a dominant-negative SNARE variant in glia. Also, CNO-mediated release was relatively insensitive to N-type calcium channel blockade. Systemic administration of CNO inhibited cue-induced reinstatement of cocaine seeking in rats extinguished from cocaine, but not sucrose SA. The capacity to inhibit reinstated cocaine-seeking was prevented by systemic administration of the group II metabotropic glutamate receptor (mGluR2/3) antagonist LY341495. Conclusions DREADD-mediated glutamate gliotransmission inhibited cue-induced reinstatement of cocaine seeking by stimulating release-regulating mGluR2/3 autoreceptors to inhibit cue-induced synaptic glutamate spillover.

Glial and Neuroimmune Mechanisms as Critical Modulators of Drug Use and Abuse

“…Electrochemical recordings demonstrated that astroglial G q -DREADD activation results in a reliable increase of glutamate release in the NAc core, and this manipulation is associated with an inhibition of cueinduced cocaine seeking (Scofield et al, 2015). Subsequent experiments suggested that the protective effect of astroglial stimulation was related to synaptic signaling for metabotropic glutamate receptors mGluR2/3 (Scofield et al, 2015). These data suggest that astrocytes can directly influence drug-seeking behavior for cocaine, and the methodologies employed emphasize the opportunities for glial cell-type-specific manipulations in the context of addiction.…”

“…To manipulate intracellular calcium signaling in a discrete population of astrocytes, the authors utilized viral mediated transfection to express the designer receptor exclusively activated by a designer drug (DREADD) hM3D (a designer G q -protein coupled receptor) under the control of the GFAP promoter (Scofield et al, 2015). This method allows for pharmacological control of astrocyte intracellular signaling.…”

“…This method allows for pharmacological control of astrocyte intracellular signaling. Electrochemical recordings demonstrated that astroglial G q -DREADD activation results in a reliable increase of glutamate release in the NAc core, and this manipulation is associated with an inhibition of cueinduced cocaine seeking (Scofield et al, 2015). Subsequent experiments suggested that the protective effect of astroglial stimulation was related to synaptic signaling for metabotropic glutamate receptors mGluR2/3 (Scofield et al, 2015).…”

The Nucleus Accumbens: Mechanisms of Addiction across Drug Classes Reflect the Importance of Glutamate Homeostasis

“…Physiological analyses reveal that cocaine-and heroin-induced loss of LTD and LTP induced in the NAcore after in vivo electrical stimulation of the PFC is reversed by daily NAC treatment Shen and Kalivas, 2013). Interestingly, the ability Scofield et al, 2015 xCT, the catalytic subunit of the cystine-glutamate exchanger.…”

Medial habenula cholinergic signaling regulates cocaine‐associated relapse‐like behavior

“…Others have demonstrated that CNO alone has no effect on reinstatement behaviors or psychostimulant self-administration (Ferguson et al 2011;Mahler et al 2014;Scofield et al 2015;Augur et al 2016;Kerstetter et al 2016). However, Gomez et al implicate clozapine as the specific ligand to DREADDs and its back metabolism from CNO to engage DREADD-mediated changes in cell function (2017).…”