Prepubertal ovarian inhibition of Light/Dark Box exploration and novel object investigation in juvenile Siberian hamsters

Testosterone facilitates nonreproductive, context-appropriate pro- and anti-social behavior in female and male Mongolian gerbils

A growing body of literature suggests that testosterone (T) rapidly modulates behavior in a context-specific manner. However, the timescales in which T can rapidly mediate distinct types of behavior, such as pro- vs. anti- social responses, has not been studied. Thus, here we examined acute T influences on social behavior in male and female Mongolian gerbils in nonreproductive contexts. Females and males received an injection of either saline or T and were first tested in a social interaction test with a same-sex, familiar peer. 5 min after the peer interaction, subjects then underwent a resident-intruder test with a novel, same-sex conspecific. After another 5 min, gerbils were tested in a novel object task to test context-specificity (i.e., social vs. nonsocial) of T effects on behavior. Within 1 h, males and females injected with T exhibited more huddling with a peer but more active avoidance of and less time spent in proximity of an intruder than did animals injected with saline. T effects on behavior were specific to social contexts, such that T did not influence investigation of the novel object. Together these findings show that T rapidly promotes pro-social responses to a familiar peer and anti-social responses to an intruder in the same individuals within 5 min of experiencing these disparate social contexts. This demonstrates that T rapidly facilitates behavior in a context-appropriate manner outside the context of reproduction and reveals that rapid effects of T on behavior are not restricted to males.

Prepubertal ovariectomy confers resilience to stress-induced anxiety in adult female mice

The increased vulnerability to stress-induced neuropsychiatric disorders in women, including anxiety disorders, does not emerge until pubertal onset, suggesting a role for ovarian hormones in organizing sex-specific vulnerability to anxiety. Parvalbumin (PV) interneurons in the prefrontal cortex are a potential target for these ovarian hormones. PV+ interneurons undergo maturation during the adolescent period and have been shown to be sensitive to stress and to mediate stress-induced anxiety in female mice. To test the idea that ovarian hormones at puberty are necessary for the acquisition of sensitivity to stress, hypothetically driving the response of PV+ interneurons to stress, we performed ovariectomy or sham surgery before pubertal onset in female mice. These mice then were exposed to four weeks of unpredictable chronic mild stress in adulthood. We then assessed anxiety-like behavior and PV/FosB colocalization in the medial PFC. Additionally, we assessed stress-induced anxiety-like behavior in female mice following ovariectomy in adulthood to determine if puberty is a sensitive period for ovarian hormones in mediating vulnerability to stress. We found that prepubertal ovariectomy protects against the development of anxiety-like behavior in adulthood, an effect not found following ovariectomy in adulthood. This effect may be independent of ovarian hormones on prefrontal PV+ interneurons response to stress.

Suppression of ovarian hormones in adolescent rats has no effect on anxiety-like behaviour or c-fos activation in the amygdala

In humans, sex differences in mood disorders emerge during adolescence, with prevalence rates being consistently higher in females than males. It has been hypothesised that exposure to endogenous ovarian hormones during adolescence enhances the susceptibility of females to mood disorders from this stage of life onwards. However, experimental evidence in favour of this hypothesis is lacking. In the present study, we examined the long-term effects of suppressing adolescent gonadal hormone levels in a group of female Lister-hooded rats via administration of a gonadotrophin-releasing hormone antagonist (Antide; administered on postnatal day [PND] 28 and 42) compared to control females and males (n = 14 per group). We predicted that, in adulthood, Antide-treated female rats would exhibit more male-like behaviour than control females in novel environments (elevated-plus maze, open field and light-dark box), in response to novel objects and novel social partners, and in an acoustic startle task. Progesterone and luteinising hormone assays (which were conducted on blood samples collected on PND 55/56 and 69/70) confirmed that the hypothalamic-pituitary-gonadal axis was temporarily suppressed by Antide treatment. In addition, Antide-treated females were found to exhibit a modest pubertal delay, as measured by vaginal opening, which was comparable in length to the pubertal delay that has been induced by adolescent exposure to alcohol or stress in previous studies of female rats. However, Antide-treated females did not substantially differ from control females on any of the behavioural tests, despite the evidence for predicted sex differences in some measures. Following the acoustic startle response task, all subjects were culled and perfused, and c-Fos staining was conducted in the medial and basolateral amygdala, with the results showing no significant differences in cell counts between the groups. These findings suggest that ovarian hormone exposure during adolescence does not have long-term effects on anxiety-related responses in female rats.

Paeonol at Certain Doses Alleviates Aggressive and Anxiety-Like Behaviours in Two Premenstrual Dysphoric Disorder Rat Models

Premenstrual dysphoric disorder (PMDD) is a severe form of premenstrual syndrome (PMS), a common mental health disturbance associated with several periodic psychological symptoms in women. Selective serotonin reuptake inhibitors (SSRIs) are the first-line treatment for PMS/PMDD patients; however, side effects are inevitable, especially in long-term treatment. In previous studies, the natural compound paeonol in Moutan Cortex was found to play effective roles in central nervous system disorders with its anti-inflammatory, anti-oxidant, and neuroprotective effects. Consequently, we assume that paeonol might produce positive effects in the treatment of PMS/PMDD. In this study, the open-field test (OFT) and elevated plus maze (EPM) and light dark box (LDB) tests were performed in mice to determine the optimal dose of paeonol for treating anxiety. Then, paeonol was used to treat the progesterone withdrawal (PWD) and resident intruder paradigm (RIP) rat models of PMDD. Using these two reliable models, the OFT and EPM, LDB, and composite aggressive tests were performed to evaluate the effect of the drug on behavioural symptoms of PMDD. From the dosage screening results, the optimal anti-anxiety dose of paeonol was identified as 17.5 mg/kg/d for 7 days. With regard to the effect of paeonol on PMDD rat models, a significantly improvement was found in the behavioural symptoms, but the effective dose varied in different models. For the PWD model rats, treatment with 6.05 mg/kg paeonol could significantly improve anxiety and irritability, while that with 24.23 mg/kg paeonol resulted in anxiety-like effects in behavioural tests. In RIP model rats, treatment with 12.11 mg/kg paeonol demonstrated excellent effects in improving anxiety, particularly irritable emotional behaviour. In conclusion, our study indicates that paeonol is a potential therapeutic compound for PMS/PMDD; it is a drug option that helps establish dosage guidance for treatment of this condition.