Fisher, Z. D. G. | Search bioRxiv

bioRxiv2025

Chronic stress facilitates behavioral engagement and alters lateral habenula activity during flexible decision making in a sex-dependent manner

The ability to integrate feedback and flexibly adjust behavior under shifting environmental demands is required to optimize decision-making strategies. Clinical and preclinical data indicate that individuals with stress-related disorders and rodents exposed to chronic stress exhibit impaired behavioral flexibility. The lateral habenula (LHb) has emerged as a key brain region contributing to the effects of stress on cognitive performance. However, the extent to which the LHb is recruited to fine-tune decision-making strategies, as well as the impacts of chronic stress on LHb recruitment during task performance, remain largely unknown. To this end, we used a three-week model of chronic unpredictable stress (CUS) and performed in vivo fiber photometry to investigate Ca2+ transients in LHb neurons during an attentional set-shifting task in adult male and female Sprague Dawley rats (n=7-12/sex/group). We found that CUS exposure did not significantly impair behavioral flexibility. Rather, CUS-exposed rats made fewer omissions and exhibited shorter response latencies compared to controls, suggesting enhanced task engagement. We also observed sex differences in LHb Ca2+ activity. In control animals, we found that male rats showed stronger LHb signal prior to decision making, and greater activation following trial outcome than females. These differences were normalized by CUS, resulting in similar signaling patterns across sexes. Altogether, these findings reveal that chronic stress alters LHb activity in a sex-dependent manner without overtly impairing behavioral flexibility, thereby underscoring the importance of the LHb in decision making under stressful conditions. HighlightsO_LIChronic stress decreased response latency without impairing behavioral flexibility C_LIO_LIMale rats displayed greater inhibition of LHb activity prior to decision making C_LIO_LIChronic stress abolished sex differences in LHb activity during decision making C_LI

neuroscience↗

bioRxiv2024

Maternal cannabis use alters excitatory inputs to corticostriatal efferent neurons in rat offspring

With the recent surge in cannabis legalization across North America, there is legitimate concern that rates of cannabis use during pregnancy will dramatically increase in the coming years. However, the long-term impacts of prenatal cannabis exposure (PCE) on the brain and behavior remain poorly understood. Using a model of passive cannabis vapor exposure, we have previously shown that PCE impairs behavioral flexibility in an attentional set-shifting task in adult offspring, which is orchestrated in part by excitatory inputs from the medial prefrontal cortex (mPFC) to the nucleus accumbens (NAc). Given the fundamental role of these corticostriatal inputs in coordinating flexible reward-seeking strategies, we used a combination of retrograde tracing and ex vivo electrophysiology to test the hypothesis that maternal cannabis use alters the synaptic and intrinsic membrane properties of corticostriatal efferent neurons in exposed male and female rat offspring. Specifically, pregnant rat dams were trained to self-administer vaporized cannabis (69.7% THC; 150 mg/ml) twice daily throughout mating and gestation and offspring were subsequently injected with fluorescent retrobeads into the NAc core prior to conducting whole-cell ex vivo recordings of spontaneous excitatory and inhibitory post-synaptic currents (EPSC and IPSC, respectively) in retrolabeled mPFC neurons in adulthood. Our results indicate that PCE increases the frequency of spontaneous glutamatergic events (EPSCs) in NAc-projecting mPFC neurons in a sex-specific manner, which drives changes in excitatory to inhibitory (EPSC/IPSC) ratio, particularly in females. Furthermore, the amplitude of phasic glutamatergic events was reduced in cannabis-exposed offspring of both sexes, suggesting changes in postsynaptic receptor function. Altogether, these data demonstrate that PCE shifts the balance of excitatory/inhibitory inputs onto NAc-projecting mPFC neurons with limited effects on membrane conductance in females, resulting in reduced sex differences following maternal cannabis self-administration. These results provide putative neurophysiological mechanisms mediating previously observed behavioral changes, and future studies will need to test if these cannabis-induced changes are causal to long-term deficits in behavioral flexibility that have been previously documented in exposed offspring.

neuroscience↗