Effects of prenatal stress on neuroactive steroid responses to acute stress in adult male and female rats

Acute swim stress results in the robust production of several neuroactive steroids, which act as mediators of the stress response. These steroids include glucocorticoids, and positive GABAA receptor modulatory steroids such as allopregnanolone and tetrahydrocorticosterone (THDOC), which potentiate inhibitory GABA signalling, thereby playing a role in the negative control of the hypothalamo‐pituitary‐adrenal (HPA) axis. Prenatally stressed (PNS) offspring exhibit increased vulnerability to stress‐related disorders and frequently display exaggerated HPA axis responses to stressors during adulthood, which may be a result of reduced neuroactive steroid production and consequently inhibitory signalling. Here, we investigated in rats whether exposure to prenatal social stress from gestational day 16‐20 altered neuroactive steroid production under non‐stress conditions and in response to an acute stressor (swim stress) in adulthood. Using liquid chromatography‐mass spectrometry, nine neuroactive steroids were quantified (corticosterone, deoxycorticosterone (DOC), dihydrodeoxycorticosterone (DHDOC), THDOC, progesterone, DHP, allopregnanolone, pregnenolone, testosterone) in plasma and in five brain regions (frontal cortex, hypothalamus, amygdala, hippocampus, brainstem) of male and female control and PNS rats.
There was no difference in the neuroactive steroid profile between control and PNS rats under basal conditions. The increase in circulating corticosterone induced by acute swim stress was similar in control and PNS offspring. However, greater stress‐induced corticosterone and DOC concentrations were observed in the brainstem of male PNS offspring, whereas DOC concentrations were lower in the hippocampus of PNS females compared with controls, following acute stress. While PNS rats did not show deficits in allopregnanolone responses to acute stress, there were modest deficits in the production of THDOC in the brainstem, amygdala, and frontal cortex of PNS males and in the frontal cortex of PNS females. The data suggest that neuroactive steroid modulation of GABAergic signalling following stress exposure may be affected in a sex‐ and region‐specific manner in PNS offspring.