Background Relapse to cocaine-seeking has been linked with low glutamate in the nucleus accumbens core (NAcore) causing potentiation of synaptic glutamate transmission from prefrontal cortex (PFC) afferents. Systemic N-acetylcysteine (NAC) has been shown to restore glutamate homeostasis, reduce relapse to cocaine-seeking and depotentiate PFC-NAcore synapses. Here we examine the effects of NAC applied directly to the NAcore on relapse and neurotransmission in PFC-NAcore synapses, as well as the involvement of the metabotropic glutamate receptors (mGluRs) mGluR2/3 and mGluR5. Methods Rats were trained to self-administer cocaine for 2 weeks and following extinction received either intra-accumbens NAC or systemic NAC 30 or 120 minutes, respectively, prior to inducing reinstatement with a conditioned cue or a combined cue and cocaine injection. We also recorded postsynaptic currents using in vitro whole cell recordings in acute slices and measured cystine and glutamate uptake in primary glial cultures. Results NAC microinjection into the NAcore inhibited the reinstatement of cocaine-seeking. In slices, a low concentration of NAC reduced the amplitude of evoked glutamatergic synaptic currents in the NAcore in a mGluR2/3-dependent manner, while high doses of NAC increased amplitude in a mGluR5-dependent manner. Both effects depended on NAC uptake through cysteine transporters and activity of the cysteine/glutamate exchanger. Finally, we showed that by blocking mGluR5 the inhibition of cocaine-seeking by NAC was potentiated. Conclusions The effect of NAC on relapse to cocaine-seeking depends on the balance between stimulating mGluR2/3 and mGluR5 in the NAcore, and the efficacy of NAC can be improved by simultaneously inhibiting mGluR5.

Previous studies have demonstrated that combined total sleep deprivation (Wake therapy), sleep phase advance, and bright light therapy (Triple Chronotherapy) produce a rapid and sustained antidepressant effect in acutely depressed individuals. To date no studies have explored the impact of the intervention on unipolar depressed individuals with acute concurrent suicidality. Participants were suicidal inpatients (N=10, Mean age=44±16.4SD, 6F) with unipolar depression. In addition to standard of care, they received open label Triple Chronotherapy. Participants underwent one night of total sleep deprivation (33–36 hours), followed by a three-night sleep phase advance along with four 30-minute sessions of bright light therapy (10,000 lux) each morning. Primary outcome measures included the 17 item Hamilton depression scale (HAM17), and the Columbia Suicide Severity Rating Scale (CSSRS), which were recorded at baseline prior to total sleep deprivation, and at protocol completion on day five. Both HAM17, and CSSRS scores were greatly reduced at the conclusion of the protocol. HAM17 scores dropped from a mean of 24.7±4.2SD at baseline to a mean of 9.4±7.3SD on day five (p=.002) with six of the ten individuals meeting criteria for remission. CSSRS scores dropped from a mean of 19.5±8.5SD at baseline to a mean of 7.2±5.5SD on day five (p=.01). The results of this small pilot trial demonstrate that adjunctive Triple Chronotherapy is feasible and tolerable in acutely suicidal and depressed inpatients. Limitations include a small number of participants, an open label design, and the lack of a comparison group. Randomized controlled studies are needed.

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Intrusive thinking triggers clinical symptoms in many neuropsychiatric disorders. Using drug addiction as an exemplar disorder sustained in part by intrusive thinking, we explore studies demonstrating that impairments in corticostriatal circuitry strongly contribute to intrusive thinking. Neuroimaging studies have long implicated this projection in cue-induced craving to use drugs, and preclinical models show that marked changes are produced at corticostriatal synapses in the nucleus accumbens during a relapse episode. We delineate an accumbens microcircuit that mediates cue-induced drug seeking becoming an intrusive event. This microcircuit harbors many potential therapeutic targets. We focus on preclinical and clinical studies, showing that administering N-acetylcysteine restores uptake of synaptic glutamate by astroglial glutamate transporters and thereby inhibits intrusive thinking. We posit that because intrusive thinking is a shared endophenotype in many disorders, N-acetylcysteine has positive effects in clinical trials for a variety of neuropsychiatric disorders, including drug addiction, gambling, trichotillomania, and depression.