Biology subjects

Bourgeois, J. R.

Publications and source records attributed to Bourgeois, J. R..

2 recordsLinked to original sources

bioRxiv2021

Sex differences in choice-based thermal nociceptive tasks in adult rats

Interest in the role of sex as a biological variable continues to increase, including a mandate for the study of both sexes in NIH-funded research. Choice-based thermal nociceptive tests allow for the study of a more spontaneous response to thermal stimuli and avoidance behavior compared to traditional nociceptive assays, and their usage has been increasing in recent years. However, to date no comparison of naive male and female responses to such tests has been published. As sex differences are known to exist in both human chronic pain conditions and rodent models of nociception, it is critical to understand the impact of sex on any nociceptive assay. Herein, we examined the effect of sex on two choice-based thermal nociceptive tests, the thermal gradient test and the temperature place preference test, in adult rats. We report that marked sex differences exist in responses to these tests. Namely, the activation of a 10{degrees} C-to-47{degrees} C thermal gradient results in an increase in time spent in the 10{degrees} C zone in females, compared to a reduction in males. In a temperature place preference test pairing a surface temperature of 22{degrees} C with either 5{degrees} C, 10{degrees} C, 47{degrees} C, or 50{degrees} C, males spent less than 50% of their time in every non-22{degrees} C zone, but in females this was only observed when testing 50{degrees} C. Together, these results suggest that male rats show more avoidance behavior to non-ambient temperatures when given free access to multiple zones, including at temperatures which are milder than those typically used to evoke a nociceptive response in traditional hot and cold plate tests.

neuroscience↗

bioRxiv2021

Morphine exposure bidirectionally alters c-Fos expression in a sex-, age-, and brain region-specific manner during adolescence

Drug and alcohol use during adolescence is common, and data in both humans and preclinical animal models clearly indicate drug exposure during adolescence increases the risk of substance use and other mental health disorders later in life. Adolescence is a period of social, emotional, and cognitive development, and is characterized by increased exploratory behavior, risk-taking, and peer-centered social interactions. These are thought to be behavioral manifestations of developmental plasticity in reward regions of the brain. Human data indicate that adolescence is not a unitary developmental period, but rather different neural and behavioral sequelae can be observed in early vs. late adolescence. However, most studies with rodent models examine a single adolescent age compared to a mature adult age, and often only in males. Herein, we sought to determine whether the acute response to the opioid morphine would also differ across adolescence, and by sex. By quantifying c-Fos positive cells, a proxy for neural activity, at different stages during adolescence (pre-, early, mid-, and late adolescence) and in multiple reward regions (prefrontal cortex, nucleus accumbens, caudate/putamen), we determined that acute morphine can either reduce or increase c-Fos expression dependent on adolescent age, sex, and brain region. These data suggest that heterogeneity in the consequences of adolescent opioid exposure may be due to the interaction between age- and sex-specific developmental profiles of reward processing in individual brain regions. In future studies, it will be important to add age within adolescence as an independent variable to fully capture the consequences of healthy or abnormal reward-related neural development.

neuroscience↗