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Early-life adversity (ELA) increases the likelihood of neuropsychiatric diagnoses, which are more prevalent in women than men. Since changes in reproductive hormone levels can also increase the probability of anxiety disorders in women, we examined the effects of ELA on adult female mice across the estrous cycle. We found that during diestrus, when progesterone levels are relatively high, ELA mice exhibit increased avoidance behavior and increased theta oscillation power in the ventral hippocampus (vHIP). We also found that diestrus ELA mice had higher levels of progesterone and lower levels of allopregnanolone, a neurosteroid metabolite of progesterone, in the vHIP compared with control-reared mice. Progesterone receptor antagonism normalized avoidance behavior in ELA mice, while treatment with a negative allosteric modulator of allopregnanolone promoted avoidance behavior in control mice. These results suggest that altered vHIP progesterone and allopregnanolone signaling during diestrus increases avoidance behavior in ELA mice.

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Early life adversity (ELA) increases the risk of developing neuropsychiatric illnesses such as anxiety disorders. However, the mechanisms connecting these negative early life experiences to illness later in life remain unclear. In rodents, plasticity mechanisms, specifically adult neurogenesis in the ventral hippocampus, have been shown to be altered by ELA and important for buffering against detrimental stress-induced outcomes. The current study sought to explore whether adult neurogenesis contributes to ELA-induced changes in avoidance behavior. Using the GFAP-TK transgenic model, which allows for the inhibition of adult neurogenesis, and CD1 littermate controls, we subjected mice to an ELA paradigm of maternal separation and early weaning (MSEW) or control rearing. We found that mice with intact adult neurogenesis showed no behavioral changes in response to MSEW. After reducing adult neurogenesis, however, male mice previously subjected to MSEW had an unexpected decrease in avoidance behavior. This finding was not observed in female mice, suggesting that a sex difference exists in the role of adult-born neurons in buffering against ELA-induced changes in behavior. Taken together with the existing literature on ELA and avoidance behavior, this work suggests that strain differences exist in susceptibility to ELA and that adult-born neurons may play a role in regulating adaptive behavior.

Early-life adversity (ELA) predisposes individuals to develop neuropsychiatric conditions, which are more prevalent in women than men. Efforts to model this sex difference in rodents have produced mixed results, with some studies paradoxically showing stronger phenotypes in males than females. Since changes in reproductive hormone levels can increase the likelihood of anxiety disorders in women, we examined the effects of ELA on adult female mice across the estrous cycle. We found that during diestrus, when the ratio of progesterone to estrogen is relatively high, ELA mice exhibit increased avoidance behavior, altered activity levels in specific contexts, and increased theta oscillation power in the ventral hippocampus. Ovariectomy, which eliminates circulating estrogen but not progesterone, unexpectedly preserved some of the effects present in diestrus ELA mice. Progesterone receptor antagonism in diestrus normalized avoidance behavior in ELA mice, while treatment with a negative allosteric modulator of the progesterone metabolite allopregnanolone promoted avoidance behavior in control mice. These results suggest that altered progesterone and allopregnanolone signaling during diestrus increases avoidance behavior in ELA mice

Social memory dysfunction is a feature of several neuropsychiatric and neurodevelopmental disorders. Mutation or deletion of the SHANK3 gene, which codes for a synaptic scaffolding protein, has been linked to autism spectrum disorder (ASD) and Phelan-McDermid syndrome, conditions associated with impairments in social memory. Shank3B knockout (KO) mice exhibit several behavioral abnormalities that may be analogous to symptoms of ASD, including social discrimination deficits. The CA2 region of the hippocampus integrates numerous afferents and sends a major output to the ventral CA1 (vCA1), circuitry that plays an important role in social memory. Despite finding few differences in excitatory afferents to the CA2 in Shank3B KO mice, chemogenetic activation of CA2 excitatory neurons restored social recognition function to wildtype (WT) levels. Specific activation of the CA2-vCA1 circuitry had a similar effect. Neuronal oscillations in the theta, gamma and, sharp wave ripple ranges have been linked to social memory, but we observed no differences in these measures between WT and Shank3B KO mice in the vCA1 in response to social stimuli. However, activation of CA2 excitatory neurons enhanced vCA1 theta power in Shank3B KO mice, concurrent with behavioral improvements. These findings suggest that stimulating adult circuitry in a mouse model with neurodevelopmental impairments can be sufficient to invoke latent function, particularly with respect to social memory dysfunction. The extent to which vCA1 network oscillations in the theta range are responsible for rescued behavioral function remains unknown.

Early-life adversity (ELA) predisposes individuals to develop neuropsychiatric conditions, which are more prevalent in women than men. Efforts to model this sex difference in rodents have produced mixed results, with some studies paradoxically showing stronger phenotypes in males than females. Since changes in reproductive hormone levels can increase the likelihood of anxiety disorders in women, we examined the effects of ELA on adult female mice across the estrous cycle. We found that during diestrus, when the ratio of progesterone to estrogen is relatively high, ELA mice exhibit increased avoidance behavior, altered activity levels in specific contexts, and increased theta oscillation power in the ventral hippocampus. Ovariectomy, which eliminates circulating estrogen but not progesterone, unexpectedly preserved some of the effects present in diestrus ELA mice. Progesterone receptor antagonism in diestrus normalized avoidance behavior in ELA mice, while treatment with a negative allosteric modulator of the progesterone metabolite allopregnanolone promoted avoidance behavior in control mice. These results suggest that altered progesterone and allopregnanolone signaling during diestrus increases avoidance behavior in ELA mice.

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