Sexual Experience Promotes Adult Neurogenesis in the Hippocampus Despite an Initial Elevation in Stress Hormones

Aversive stressful experiences are typically associated with increased anxiety and a predisposition to develop mood disorders. Negative stress also suppresses adult neurogenesis and restricts dendritic architecture in the hippocampus, a brain region associated with anxiety regulation. The effects of aversive stress on hippocampal structure and function have been linked to stress-induced elevations in glucocorticoids. Normalizing corticosterone levels prevents some of the deleterious consequences of stress, including increased anxiety and suppressed structural plasticity in the hippocampus. Here we examined whether a rewarding stressor, namely sexual experience, also adversely affects hippocampal structure and function in adult rats. Adult male rats were exposed to a sexually-receptive female once (acute) or once daily for 14 consecutive days (chronic) and levels of circulating glucocorticoids were measured. Separate cohorts of sexually experienced rats were injected with the thymidine analog bromodeoxyuridine in order to measure cell proliferation and neurogenesis in the hippocampus. In addition, brains were processed using Golgi impregnation to assess the effects of sexual experience on dendritic spines and dendritic complexity in the hippocampus. Finally, to evaluate whether sexual experience alters hippocampal function, rats were tested on two tests of anxiety-like behavior: novelty suppressed feeding and the elevated plus maze. We found that acute sexual experience increased circulating corticosterone levels and the number of new neurons in the hippocampus. Chronic sexual experience no longer produced an increase in corticosterone levels but continued to promote adult neurogenesis and stimulate the growth of dendritic spines and dendritic architecture. Chronic sexual experience also reduced anxiety-like behavior. These findings suggest that a rewarding experience not only buffers against the deleterious actions of early elevated glucocorticoids but actually promotes neuronal growth and reduces anxiety

Chronic gestational stress leads to depressive-like behavior and compromises medial prefrontal cortex structure and function during the postpartum period.

Postpartum depression, which affects approximately 15% of new mothers, is associated with impaired mother-infant interactions and deficits in cognitive function. Exposure to stress during pregnancy is a major risk factor for postpartum depression. However, little is known about the neural consequences of gestational stress. The medial prefrontal cortex (mPFC) is a brain region that has been linked to stress, cognition, maternal care, and mood disorders including postpartum depression. Here we examined the effects of chronic gestational stress on mPFC function and whether these effects might be linked to structural modifications in the mPFC. We found that in postpartum rats, chronic gestational stress resulted in maternal care deficits, increased depressive-like behavior, and impaired performance on an attentional set shifting task that relies on the mPFC. Furthermore, exposure to chronic stress during pregnancy reduced dendritic spine density on mPFC pyramidal neurons and altered spine morphology. Taken together, these findings suggest that pregnancy stress may contribute to postpartum mental illness and its associated symptoms by compromising structural plasticity in the mPFC

Less Can Be More: Fine Tuning the Maternal Brain

International audiencePAWLUSKI, J.L., Hoekzema, E., Leuner, B., and Lonstein, J.S. Less can be more: Fine tuning the maternal brain. NEUROSCI BIOBEHAV REV (129) XXX-XXX, 2022. Plasticity in the female brain across the lifespan has recently become a growing field of scientific inquiry. This has led to the understanding that the transition to motherhood is marked by some of the most significant changes in brain plasticity in the adult female brain. Perhaps unexpectedly, plasticity occurring in the maternal brain often involves a decrease in brain volume, neurogenesis and glial cell density that presumably optimizes caregiving and other postpartum behaviors. This review summarizes what we know of the 'fine-tuning' of the female brain that accompanies motherhood and highlights the implications of these changes for maternal neurobehavioral health. The first part of the review summarizes structural and functional brain changes in humans during pregnancy and postpartum period with the remainder of the review focusing on neural and glial plasticity during the peripartum period in animal models. The aim of this review is to provide a clear understanding of when 'less is more' in maternal brain plasticity and where future research can focus to improve our understanding of the unique brain plasticity occurring during matrescence

Acute sexual experience enhances cell proliferation in the dentate gyrus despite elevated glucocorticoid levels.

<p>Compared to naive controls, a single sexual experience elevated (a) corticosterone levels and (b) the number of proliferating cells (labeled with BrdU and examined after a 2 h survival). Bars represent mean ± SEM, ^*<i>P</i><0.05.</p

Sexual experience reduces some measures of anxiety-like behavior.

<p>(a) Compared to naive controls, sexual experience reduced anxiety-like behavior on the novelty suppressed feeding paradigm. (b) Home cage food consumption was unaltered. In contrast, anxiety-like behavior in the elevated plus maze was unaffected by sexual experience. (c) Percent time in the opens arms as well as (d) open and closed arm entries were similar in naive and sexually-experienced rats. Bars represent mean ± SEM, ^*<i>P</i><0.05.</p

Sexual behavior on day 1, 7, and 14 of male rats (n = 6) exposed to a sexually-receptive female daily for 14 consecutive days.

<p>There was no difference across days in the average number of mounts, intromissions, or ejaculations displayed during a 30 min exposure to a hormonally-primed sexually receptive female. Numbers represent mean ± SEM. <i>P</i>>0.05 for all comparisons, repeated measures ANOVA.</p

Chronic gestational stress impairs cognitive flexibility.

<p>Compared to postpartum females who were unstressed, postpartum females stressed in pregnancy showed impairments on the reversal (REV) and extra dimensional (EDS) phases of the attentional set shifting task as demonstrated by more trials (a) and errors (b) to reach criterion. The number of trials (a) and errors (b) to reach criterion for the simple discrimination (SD), compound discrimination (CD) and intradimensional shift (IDS) did not differ between unstressed and stressed mothers. Bars represent mean ± SEM, * <i>p</i><0.05.</p

Behavioral protocol for attentional set shifting.

<p>Representative example of stimulus pairs and the progression through stages of the attentional set shifting task. Digging medium was the initial discriminative stimulus dimension, shifting to texture in the EDS stage. For each stage, the positive stimulus is in bold and is paired randomly across trials with the two stimuli from the irrelevant dimension.</p