Abstract
This work evaluated the influence of chronic mild stress on latent inhibition (LI) in rats, using a conditioned emotional response (CER) procedure. Rats were assigned to four groups: a non pre-exposed control group (NPC), a non pre-exposed stressed group (NPS), a preexposed control group (PC), and a pre-exposed stressed group (PS). Stressed animals were submitted to a chronic mild stress (CMS) regimen for three weeks. The off-baseline conditioned emotional response procedure had four phases: licking response training, tone- shock conditioning, retraining, and testing. Conditioning consisted of 2 tone (30 s) and shock (0.5 s) associations. Tone-shock conditioning evidenced by NPS and NPC groups suggests that stress did not interfere with the expression of a conditioned emotional response. Pre-exposure was carried out using 6 tones (30 s) during 2 sessions before conditioning. Prior exposure to the tone resulted in a decrease in learning that was greater in stressed animals. The results indicate an increase in latent inhibition induced by chronic mild stress. Such LI potentiation after CMS may be related to dopamine (DA) neurotransmission reduction in the central nervous system.
Highlights
Latent inhibition (LI) refers to the procedure, non-reinforced pre-exposure to a stimulus, and to the behavioral outcome, characterized by a delay A.L
The results show that there was a decrease in expression of conditioned emotional response (CER) induced by the chronic mild stress in the pre-exposed condition
The present study induced the learning of a conditioned emotional response in two groups of rats, one submitted to intermittent unpredictable mild stress for a prolonged period and another comprising control non-stressed rats
Summary
Latent inhibition (LI) refers to the procedure, non-reinforced pre-exposure to a stimulus, and to the behavioral outcome, characterized by a delay A.L. This research was designed to investigate the effects of CMS on the LI phenomenon in rats using a conditioned emotional response (CER) paradigm based on behavioral suppression. Beginning on the 14th day of stress induction, the rats were submitted to an off-baseline conditioned response suppression consisting of the following 5 phases: initial shaping, pre-exposure, conditioning, reshaping, and testing.
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