EN
The individual differences in the response to aversive stimuli could be important predictor for anxiety and affective disorder. Recently, in our laboratory we evaluated model of high (HR) and low anxiety rats (LR), selected according to their behaviour in the contextual fear test (i.e., the duration of a freezing response was used as a discriminating variable) to examine the neurochemical background of differences in the individual responses to conditioned aversive stimuli. Both groups had different behavioural and biochemical profiles. During test session of conditioned freezing test, LR, had higher c-Fos activity and stronger 5-HT and CRF related immunostaining in the M2 (secondary motor cortex) and higher c-Fos in the DG of hippocampus in comparison to HR. LR vocalised more in the aversive band (22 Hz) during test session, and had higher serum levels of corticosterone and higher GABA levels in BLA. HR showed also an increase in c-Fos activity and CRF related immunostaining in BLA. We found that HR rats showed a significant decrease in the conditioned fear response over the course of two extinction sessions. Upon re-testing (24 h after the conditioned fear re-training), the fear-controlled freezing behaviour of HR rats partially returned at levels below the pre-extinction value. The behaviour of the LR group remained unchanged at each stage of the experiment. The re-exposure to conditioned fear on re-test activates the prefrontal cortex and limbic areas (increased expression of c-Fos, glucocorticoid receptor, alpha-2 subunit of GABA-A receptor, gephyrin and NR2B subunit of NMDA receptor) in HR rats.