Adolescent male and female rats show enhanced latent inhibition of conditioned fear compared to adult rats

TL;DR

Adolescent rats, both male and female, show stronger latent inhibition of fear compared to adults, suggesting a natural resilience during adolescence.

Contribution

The study reveals that adolescents have enhanced latent inhibition of conditioned fear compared to adults, contrary to expectations.

Findings

Adolescent rats showed enhanced latent inhibition compared to adults, indicated by reduced freezing after pre-exposure to a cue.

Estrous cycle had no effect on latent inhibition in female rats at any age.

Benign pre-exposure to a cue reduces subsequent fear conditioning more strongly in adolescents than in adults.

Abstract

Latent inhibition is diminished associative memory because of pre-exposure to the conditioned stimulus without any consequences. Latent inhibition likely plays a significant role in the ontogeny of anxiety disorders, contributing to why anxiety disorders are particularly prevalent in adolescence. Therefore, the present study examined latent inhibition of conditioned fear in adolescent and adult rats of each sex. Given that adolescence is associated with deficits in fear extinction, we hypothesized that latent inhibition will be impaired in adolescents compared to adults and expected females to show age-specific estrous cycle effects.

On day 1, male (Experiment 1) and female (Experiment 2) rats were placed in fear conditioning chambers. Half of the rats received pre-exposure to the tone cue while the other half received nothing. On day 2, all rats were placed back in the same chambers and exposed to three cue-footshock pairings. Latent inhibition was tested on day 3 with 20 presentations of the cue by itself in the same chamber.

We unexpectedly observed enhanced latent inhibition in adolescents compared to adults in both male and female rats, indicated by lower levels of freezing due to pre-exposure to the cue. Estrous cycle did not affect latent inhibition at any age.

These results suggest that benign experience to a cue reduces subsequent conditioning to the cue more potently in adolescence compared to adulthood, which suggests a potential resilience mechanism naturally occurring in adolescence.

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