Engagement of lateral habenula in the extinction of the appetitive conditioned responses

A visual circuit related to the habenula mediates the prevention of cocaine relapse by bright light treatment

Despite significant advancements in our understanding of addiction at the neurobiological level, a highly effective extinction procedure for preventing relapse remains elusive. In this study, we report that bright light treatment (BLT) administered during cocaine withdrawal with extinction training prevents cocaine-driven reinstatement by acting through the thalamic-habenular pathway. We found that during cocaine withdrawal, the lateral habenula (LHb) was recruited, and inhibition of the LHb via BLT prevented cocaine-driven reinstatement. We also demonstrated that the effects of BLT were mediated by activating LHb-projecting neurons in the ventral lateral geniculate nucleus and intergeniculate leaflet (vLGN/IGL) or by inhibiting postsynaptic LHb neurons. Furthermore, BLT was found to improve aversive emotional states induced by drug withdrawal. Our findings suggest that BLT administered during the cocaine withdrawal may be a promising strategy for achieving drug abstinence.

Lateral habenula lesions impair the association of a conditioned stimulus with the absence of an unconditioned stimulus: Retardation task

Recent studies have indicated that the lateral habenula (LHb) mediates the association of a conditioned stimulus (CS) with the absence of an unconditioned stimulus (US). We generated a CS-no US association using an explicit unpaired training procedure and evaluated the conditioned inhibitory properties using the modified version of the retardation-of-acquisition procedure, one of the procedures for assessing conditioned inhibition. First, rats in the unpaired group received explicit unpaired light (CS) and food (US) presentations, followed by light-food pairings. Rats in the comparison group received paired training alone. The rats in the two groups showed increased food-cup responses to light over paired training. However, rats in the unpaired group showed a slower acquisition of light and food excitatory conditioning than those in the comparison group. Light acquired conditioned inhibitory properties through explicitly unpaired training, as evidenced by its slowness. Second, we examined the effects of the LHb lesions on the decremental effects of unpaired learning on subsequent excitatory learning. Sham-operated rats exhibited decremental effects of unpaired learning on subsequent excitatory learning, while rats with LHb neurotoxic lesions did not. Third, we tested whether preexposure to the same number of lights presented in the unpaired training retarded the acquisition of subsequent excitatory conditioning. Preexposure to light did not significantly retard the acquisition of subsequent excitatory associations, with no LHb lesion effects. These findings indicate that LHb is critically involved in the association between CS and the absence of US.

Frustrative nonreward and the basal ganglia: Chemogenetic inhibition and excitation of the nucleus accumbens and globus pallidus externus during reward downshift

Frustrative nonreward contributes to anxiety disorders and addiction, and is included in the Research Domain Criteria initiative as a relevant endophenotype. These experiments explored the role of the basal ganglia in consummatory reward downshift (cRD) using inhibitory and excitatory DREADDs (designer receptors exclusively activated by designer drugs) infused in either the nucleus accumbens (NAc) or one of its downstream targets, the globus pallidus externus (GPe). NAc inhibition did not disrupt consummatory suppression during a 32-to-2% (Experiment 1) or 8-to-2% sucrose downshift (Experiment 2). However, NAc excitation enhanced consummatory suppression during a 32-to-2% sucrose downshift (Experiment 1). GPe inhibition caused a trend toward increased consummatory suppression after a 32-to-2% sucrose downshift, whereas GPe excitation eliminated consummatory suppression after an 8-to-2% sucrose downshift (Experiment 3). Chemogenetic manipulations of NAc and GPe had no detectable effects on open field activity. The effects of DREADD activation via clozapine N-oxide (CNO) administration were compared to controls that carried the DREADDs, but received vehicle injections. There was no evidence that CNO or vehicle injections in virus vector control (VVC) animals affected cRD or OF activity after either CNO or vehicle injections. NAc and GPe excitation led to opposite results in the cRD task, providing evidence that the basal ganglia circuit has a function in frustrative nonreward in the absence of detectable motor effects.