Dissecting PFC Endocannabinoid-THC -regulated circuits in movement behavior

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SUMMARY: Cannabis use in the U.S. has been dramatically increasing from 8.9% in 2016, to 17.5% in 2019, of U.S. citizens (age 12+) having used Cannabis in the last year. As Cannabis use increases, it is critical that we understand the biological activity of unwanted effects such as hypolocomotion that inhibit a patient’s ability to move and function normally. ∆9-Tetrahydrocannabinol (THC), the primary psychoactive compound in THC, acts as a partial agonist at the endocannabinoid (eCB) receptor, CB1R, to induce motor impairments in mice such as hypolocomotion and catalepsy. Beyond this, the neural-circuit basis of hypolocomotive responses to THC, and other CB1R agonists, remains largely unexplored. Using a novel eCB sensor GRAB-eCB2.0, in the prelimbic cortex (PrL), we observed a correlation between spontaneous movement events and eCB activity transients. These eCB transients, and replicated GCaMP6f calcium transients, are time-locked to the initiation of movement and were significantly greater in THC-treated mice compared to vehicle-treated mice. The central hypothesis of this proposal is that THC activates CB1R’s on select PrL GABAergic interneuron subpopulations, which disinhibits the glutamatergic activity within the PrL to modulate spontaneous movement. Aim 1 will determine if select GABAergic subpopulations modulate THC dependent PrL-mediated spontaneous movement. I will utilize in situ hybridization to probe differential expression patterns of GABAergic interneurons (GABA-IN’s). Combining GABA-IN-Cre lines with viral techniques and optogenetic electrophysiology, I will investigate the physiological changes induced by THC. We will measure THC-dependent changes in IPSCs as well as use cutting-edge techniques to probe the cannabinoid-dependent depolarized suppression of excitation/inhibition (DSE/DSI) in layers 2/3 to layers 5/6 contralaterally. Aim 2 will utilize fiber photometry of GABA-IN-Cre and VGLUT-Cre animals expressing cre-dependent GCaMP6f or eCB2.0 to record the specific neuronal activity and eCB levels of inhibitory and excitatory neurons during spontaneous movement of mice treated with THC and/or one of a series of pharmacological agents. We will also virally express a CRISPR-CB1R construct to eliminate CB1R from GABA-IN’s and glutamatergic neurons to determine if THC is able to produce the same changes in neuronal activity. We hypothesize that select subpopulations of GABA-IN’s mediate the THC-dependent increase in PrL activity associated with spontaneous movement. To determine the sufficiency of PrL activity in THC treated mice, GABA-IN’s and glutamatergic neurons will be optogenetically stimulated or inhibited to mediate movement. The goal of this proposal is to train me to become an independent investigator focused on the neuropharmacology of neuromodulation, leveraging training in novel approaches to decipher the mechanisms by which THC modulates prelimbic cortical activity during movement while inducing robust hypolocomotion.