Chronic Physical and Vicarious Psychosocial Stress Alter Fentanyl Consumption and Nucleus Accumbens Rho GTPases in Male and Female C57BL/6 Mice

Abstract

Chronic stress can increase the risk of developing a substance use disorder in vulnerable individuals. Numerous models have been developed to probe the underlying neurobiological mechanisms, however, most prior work has been restricted to male rodents, conducted only in rats, or introduces physical injury that can complicate opioid studies. Here we sought to establish how chronic psychosocial stress influences fentanyl consumption in male and female C57BL/6 mice. We used chronic social defeat stress (CSDS), or the modified vicarious chronic witness defeat stress (CWDS), and used social interaction to stratify mice as stress-susceptible or resilient. We then subjected mice to a 15 days fentanyl drinking paradigm in the home cage that consisted of alternating forced and choice periods with increasing fentanyl concentrations. Male mice susceptible to either CWDS or CSDS consumed more fentanyl relative to unstressed mice. CWDS-susceptible female mice did not differ from unstressed mice during the forced periods, but showed increased preference for fentanyl over time. We also found decreased expression of nucleus accumbens Rho GTPases in male, but not female mice following stress and fentanyl drinking. We also compare fentanyl drinking behavior in mice that had free access to plain water throughout. Our results indicate that stress-sensitized fentanyl consumption is dependent on both sex and behavioral outcomes to stress.

Negative emotional behavior during fentanyl abstinence is mediated by adaptations in nucleus accumbens neuron subtypes

“…The effect of fentanyl abstinence alone is less pronounced in the open-field based test because the arena, testing duration, and social target are different from the 3chamber social interaction test. The decreased social interaction we see here in the 3-chamber test is concordant with our previous work showing reduced social interaction in this test after 56 hr of fentanyl abstinence (Franco et al, 2022).…”

“…Since NAc MSNs are also important for the behavioral response to stress (Fox et al, 2020a), we provided fentanyl in the drinking water to minimize injection and handling stress. Here, and in our other work, we found mice will reliably consume fentanyl water in amounts similar to plain tap water (Franco et al, 2022). Because mice receive fentanyl as they consume water throughout the day, this method has the added benefit of mimicking intermittent drug use (vs continuous exposure) and minimizing repeated bouts of withdrawal between injections.…”

“…Male and female mice were pair housed across a perforated divider with a sex-matched mouse for the duration of the experiment (Franco et al, 2022). Each mouse was provided with a single 50 mL conical tube with a rubber stopper and ball-point sipper tube (Ancare) containing 10 µg/mL fentanyl citrate (Cayman #22659) in tap water as their sole liquid source for 5 days.…”

“…Then the experimental mouse is allowed to explore the arena for an additional 5 min with unfamiliar sex-matched adult conspecific in one of the wire mesh cups. The amount of time spent in the chamber containing the cups (empty or novel mouse) is measured with video tracking (Franco et al, 2022). For elevated plus maze, mice were placed in the center of the maze and their activity in open and closed arms was recorded over 5 min with video tracking (Fox et al, 2020a).…”

Transcriptome profiling of the ventral pallidum reveals a role for pallido-thalamic neurons in cocaine reward

“…Remarkably, levels of Nr4a1 and its target genes were not significantly changed in the VP of female mice. Recent work showed that other small GTPases from the Ras superfamily were unaltered by stress and repeated drug intake in the NAc of female mice 50 . This further suggests that drug exposure may differentially involve small GTPases in males and females, possibly through distinct transcription factor activation patterns 16 .…”