Abstract/Summary Deep brain stimulation (DBS) is a neurosurgical procedure that is used to treat neurologic and psychiatric disorders. Recent research in both animals and humans has shown that DBS may be an effective procedure for refractory addiction. We previously propose to use DBS as treatment for drug-seeking behaviors in a rat animal model, and found that high frequency DBS (HF-DBS) of the ventral striatum/nucleus accumbens (VS/NAc) impaired extinction of morphine-induced conditioned place preference (CPP), whereas low frequency DBS (LF-DBS) enhanced extinction memory (reducing drug seeking behavior). Interestingly, we also found that LF-DBS significatively shortens the persistency of the drug (LF-DBS~10 days vs sham-DBS~40 days). At the molecular level, we found that DBS-treated animals increased BDNF expression in the hippocampus (HPC). However, drug reinstatement was not significatively prevented in LF-DBS- treated animals when stimulation was applied only during extinction sessions. In this transition between the SCORE-SuRE grant cycle, we propose to further advance the knowledge in drug- seeking behavior, and in the underlying DBS’ mechanisms of action, by using pharmacological and chemogenetic approaches. Therefore, in the present study, Aim 1a-c will determine whether LF-DBS applied during extinction, in addition to provide electrical stimulation in the phase of drug reinstatement prevents drug seeking in a higher percentage of animals. Also, BDNF expression will be measured in the HPC, as well as in other brain regions, i.e., amygdala, VS/NAc, and medial prefrontal cortex (mPFC). Aim 2a will use a pharmacological approach by infusing BDNF and TrkB antagonist (ANA-12) in the VS/NAc to determine their effects in extinction of morphine CPP. Since glutamatergic neurons in the HPC encompass a subpopulation of neurons expressing BDNF, the approach in Aim 2b is to use the chemogenetic tool, known as designer receptors exclusively activated by designer drugs (DREADDs) to activate HPC glutamatergic neurons in the presence of ANA-12, to prevent extinction of morphine CPP. Activation of DREADDs will be done with clozapine N-oxide (CNO). Aim 2c will inactivate HPC-NAc glutamatergic/BDNFergic projections that will prevent the beneficial effects of LF-DBS. Our study represents a circuit-based approach to better understand the action mechanisms of drug- seeking and extinction. Because rodent models of drug extinction resemble exposure-based therapies in humans, it is possible that targeted electrical stimulation and the DBS-increased expression of pro-extinction molecules might represent an effective future approach to reduce the symptoms of addiction and opioid use disorders (OUD).

Project Narrative We previously determine that deep brain stimulation (DBS) shortens the persistency of drug seeking, while increasing BDNF expression in the hippocampus. Therefore, this research project will determine the best parameters to prevent drug reinstatement, as well as to pursue pharmacological and circuit-based studies to unravel DBS’ mechanisms of action. Since our animal model of extinction, resembles exposure-based therapies in humans, the identification of DBS-induced pro-extinction molecules in the corticomesolimbic reward circuit, combined with pharmacological treatments, represents a future approach to alleviate substance use disorders.