Neurological Mechanism Of Contextual Fear Memory Of Rat Model Of Post-traumatic Stress Disorder

OBJECTIVE: Post-traumatic stress disorder (PTSD) animal model of rat was established by a single serious foot-shock stress, and this animal model's contextual fear memory were studied according to the process of the classical pavlov fear conditioning. The focus of this study were: 1, the changing of gastrin-releasing peptide mRNA and protein during fear conditioning, and the correlation relationship between this change and fear memory. 2, the impact of Diazepam on animal model's fear memory , and the interaction between GRP and GABA during the onset of PTSD, and our research aimed to explore new method to cure PTSD.Method: Thirty male SD rats were randomly assigned to five groups: saline control, 30min+saline, 24h+saline,30min+diazepam, and 24h+diazepam. On day 1, the animals were familiarized with the shock-box for 30 minutes. Day 2 consisted of the conditioning of all the animals, the 30min+diazepam and 24h+diazepam groups were treated with diazepam(2mg/kg, IP) 30 minutes before the conditioning, and the other groups were treated with the same volume of saline. During the conditioning procedure, the animals were given 30-min IS or sham IS session (60 inescapable electric foot-shocks for 15 s at 1 mA or sham shocks of 0 mA were administered, sham IS session were only applied to saline control group). A retention test of fear conditioning was conducted 30minutes or 24 hours after the foot shock by placing the animals back into the same chamber and recording freezing behavior. Freezing was defined as a characteristic crouch position with cessation of all movement except that associated with breathing. Freezing was measured for 4 min immediately after the animal was placed in the box. Freezing was measured as a sample of freezing or not freezing every 10 sec, for a total of 25 observations. The number of observations of freezing was divided by the total number and then multiplied by 100 to obtain a percent of time spent freezing. Then the amygadala of the animals were isolated after mensuration of freezing. After the total RNA and protein were extracted from amygadala individually, semi-quantified RT-PCR were applied to measure GRP mRNA level , and semi-quantified western-bolt were applied to determine GRP protein level.Results: 1, Fear conditioning training can significantly increase the memory of conditioning context both in the 30min and 24h groups. One-way ANOVA shows that there were significant difference among the control, 30min and 24h groups(F =...