Biology subjects

Westerman, J. D.

Publications and source records attributed to Westerman, J. D..

3 recordsLinked to original sources

bioRxiv2026

Sex differences in agonistic social behavior: Effects of exercise and ovariectomy

Aggressive behavior encompasses a range of offensive and defensive responses that may be differentially influenced by sex, ovarian hormones, and physical activity. However, much of the existing research has focused on males and utilized paradigms designed to elicit aggression, leaving the expression and regulation of offensive and defensive behaviors during other forms of social interaction poorly understood. Here, we investigated the effects of sex, voluntary wheel running (VWR), and ovariectomy (OVX) on agonistic behavior during juvenile social exploration in adult Sprague-Dawley rats. Males exhibited greater offensive aggression, characterized by increased aggressive grooming and pinning, whereas females displayed more defensive kicking, darting, and avoidance. OVX selectively reduced defensive kicking without significantly affecting offensive aggression or avoidance, suggesting that distinct behavioral responses differ in their sensitivity to ovarian hormone removal. In contrast, VWR did not significantly alter any of the behaviors examined. Importantly, exploratory composite analyses revealed a significant sex difference in offensive aggression that was no longer detected when defensive behaviors were incorporated into the measure. Together, these findings demonstrate that sex differences in agonistic behavior extend beyond overall levels of aggression to distinct patterns of offensive and defensive responses. Distinguishing these behavioral categories may therefore be important for identifying how various manipulations, such as sex, ovarian hormones, and physical activity, influence agonistic behavior.

animal behavior and cognition↗

bioRxiv2026

Ovarian hormonal state at exercise initiation interacts with nigrostriatal circuitry to determine long-term voluntary exercise behavior

Despite the well-established health benefits of exercise, adherence to physical activity remains low, highlighting the need to identify biological factors that regulate the initiation and persistence of exercise behavior. Here, we tested whether ovarian hormone state at the onset of voluntary wheel running (VWR) influences both immediate and long-term exercise behavior in female rats. Females that initiated VWR during proestrus (Pro) ran farther, spent more time running, and ran at higher speeds on the first day of wheel access than females initiating VWR outside of Pro. Remarkably, initiating VWR during Pro also produced persistent increases in running distance, duration, speed, and escalation across subsequent weeks, despite normal cycling through other estrous phases. In contrast, exogenous estradiol (E2) administered at VWR initiation did not alter day-1 behavior, but increased running distance and duration across subsequent weeks without affecting running speed or escalation. To determine whether dorsal striatal dopamine contributes to these effects, we inhibited the substantia nigra (SN) to dorsolateral striatum (DLS) pathway on the first day of VWR. This manipulation reduced the immediate and long-term effects of initiating VWR during Pro on running duration and distance but not speed or escalation. These findings identify behavioral initiation as a critical window during which hormones and nigrostriatal signaling influence future engagement in physical activity. Furthermore, analysis of individual components of VWR architecture reveals that distinct features of VWR behavior can be dissociated mechanistically and thus could be used to investigate separate motivational processes underlying physical activity.

neuroscience↗

bioRxiv2024

Estrous phase during fear extinction modulates fear relapse through a nigrostriatal dopamine pathway

Elevated ovarian hormones during fear extinction can enhance fear extinction memory retention and reduce renewal, but the mechanisms remain unknown. Ovarian hormones modulate dopamine (DA) transmission, a key player in fear extinction. In males, stimulation of substantia nigra (SN) DA neurons during fear extinction reduces renewal; an effect mimicked by a DA D1 receptor agonist into the dorsolateral striatum (DLS). The current studies tested the role of the SN-DLS pathway in estrous cycle-modulation of fear extinction and relapse. In cycling female, Long-Evans rats, fear extinction during proestrus or estrus (Pro/Est; high hormones) resulted in less relapse (renewal and spontaneous recovery) compared to males or females in metestrus or diestrus (Met/Di; low hormones). This effect was mimicked by estradiol (E2) administration to ovariectomized rats. Females in Pro/Est had greater fear extinction-induced cFos within SN DA neurons compared to males. Similarly, fast scan cyclic voltammetry revealed that electrically-evoked DA release in the DLS is potentiated by E2 and is greater during Pro/Est compared to Met/Di. An inhibitory intersectional chemogenetic approach targeting the SN-DLS pathway suppressed electrically-evoked DA release in the DLS and restored fear renewal in females exposed to simultaneous fear extinction and SN-DLS inhibition during Pro/Est. Conversely, chemogenetic stimulation of the SN-DLS pathway during extinction reduced fear renewal in males. These data suggest that levels of ovarian hormones present during fear extinction modulate relapse through a SN-DLS pathway, and that the SN-DLS pathway represents a novel target for the reduction of fear relapse in both sexes.

neuroscience↗