BioRxiv. 2020 Dec 21
Geith Maal-Bared, Mandy Yee, Erika K. Harding, Martha Ghebreselassie, Michael Bergamini, Roxanne Choy, Ethan Kim, Stephanie Di Vito, Maryam Patel, Mohammadreza Amirzadeh, Taryn E. Grieder, James I. Nagy, Robert P. Bonin and Derek van der Kooya
Products used in the paper Details Operation
AAV vector packaging These coordinates were used to deliver Cre-dependent AAVs carrying Cx36 (ssAAV9-Ef1a-DIO-Cx36) and EGFP (ssAAV9-Ef1a-EGFP-WPREs) at 5E+13 GC/mL in 0.1 mL. AAVs were obtained from Packgene. Request Quote

Research Field: CNS

AAV Serotype: AAV9

Dose: These coordinates were used to deliver Cre-dependent AAVs carrying Cx36 (ssAAV9-Ef1a-DIO-Cx36) and EGFP (ssAAV9-Ef1a-EGFP-WPREs) at 5E+13 GC/mL in 0.1 mL.

Routes of Administration: Viral and tracer delivery in mice were performed by delivering 0.3 μL solution bilaterally via 1 μL Hamilton Syringes. The protocol for stereotaxic surgery in mice was similar to the one used for rats. For viral delivery into the VTA, our coordinates were identical to ones used in our previous work (Vargas-Perez et al., 2014; AP: -3.00 mm, ML: ±0.5 mm, DV: -4.2 mm from bregma)

Targeted organ: brain

Animal or cell line strain: Adult male Wistar rats (250 – 400 grams) and C57BL/6 mice (20 – 35 grams) were acquired from Charles River (Montreal, Canada).

Abstract

Drug dependence is characterized by a switch in motivation wherein a positively reinforcing substance becomes negatively reinforcing. Ventral tegmental area (VTA) GABA neurons form a point of divergence between two double dissociable pathways responsible for these respective motivational states. Here we show that this switch from drug-naïve to opiate-dependent and withdrawn (ODW) motivation is contingent upon the gap junction-forming protein, connexin-36 (Cx36), in VTA GABA neurons. Intra-VTA infusions of the Cx36 blocker, mefloquine, in ODW rats resulted in a reversion to a drug-naïve motivational state and a loss of opiate withdrawal aversions. Consistent with these data, conditional knockout mice lacking Cx36 in GABA neurons (GAD65-Cre;Cx36fl(CFP)/fl(CFP)) were perpetually drug-naïve and never experienced opiate withdrawal aversions. Further, viral-mediated rescue of Cx36 in VTA GABA neurons was sufficient to restore their susceptibility to ODW motivation. Our findings reveal a functional role for VTA gap junctions that has eluded prevailing circuit models of addiction.

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