Astrocyte Molecular Clock Function in the Nucleus Accumbens Is Important for Reward-Related Behavior

BACKGROUND: Substance use disorders are associated with disruptions in circadian rhythms. Both human and animal work have shown the integral role for circadian clocks in the modulation of reward behaviors. Astrocytes have emerged as key regulators of circadian rhythmicity. However, no studies to date have identified the role of circadian astrocyte function in the nucleus accumbens (NAc), a hub for reward regulation, or determined the importance of these rhythms for reward-related behavior. METHODS: Using astrocyte-specific RNA sequencing across time of day, we first characterized diurnal variation of the NAc astrocyte transcriptome. We then investigated the functional significance of this circadian regulation through viral-mediated disruption of molecular clock function in NAc astrocytes, followed by assessment of reward-related behaviors, metabolic-related molecular assays, and whole-cell electrophysiology in the NAc. RESULTS: Strikingly, approximately 43% of the astrocyte transcriptome has a diurnal rhythm, and key metabolic pathways were enriched among the top rhythmic genes. Moreover, mice with a viral-mediated loss of molecular clock function in NAc astrocytes show a significant increase in locomotor response to novelty, exploratory drive, operant food self-administration, and motivation. At the molecular level, these animals also show disrupted metabolic gene expression, along with significant downregulation of both lactate and glutathione levels in the NAc. Loss of NAc astrocyte clock function also significantly altered glutamatergic signaling onto neighboring medium spiny neurons, alongside upregulated glutamate-related gene expression. CONCLUSIONS: Taken together, these findings demonstrate a novel role for astrocyte circadian molecular clock function in the regulation of the NAc and reward-related behaviors.

Automated summary

This study reveals the important role of astrocyte circadian molecular clock function in the regulation of the nucleus accumbens (NAc) and reward-related behaviors. Approximately 43% of the astrocyte transcriptome shows diurnal rhythm, with key metabolic pathways enriched among the rhythmic genes. Disruption of molecular clock function in NAc astrocytes leads to increased locomotor response to novelty, exploratory drive, operant food self-administration, and motivation. These animals also exhibit disrupted metabolic gene expression, as well as altered glutamatergic signaling and gene expression in the NAc.