Anticholinergic drug atropine diminishes newly formed fear memory in male rats

Post-traumatic stress disorder (PTSD) is a condition which is triggered shortly after experiencing traumatic events. PTSD is complicated by the fact that people with PTSD often develop additional disorders such as phobias, addiction, depression, panic disorder and obsessive-compulsive disorder. Beta-adrenergic and cholinergic system both are involved in memory formation as well as in emotional response associated with memory. It is reported that the administration of beta-adrenergic and cholinergic antagonist results in the impairment in memory formation. Here, we examined the potential of beta-adrenergic antagonist propranolol and muscarinic cholinergic antagonist atropine for impairing the recently formed fear memory associated with PTSD. Reconsolidation is the memory process during which labile memory converts into permanent memory. In this study it is hypothesized that if recently formed fear memory is disturbed during reconsolidation phase by pharmacological intervention then it could be possible to impair well-consolidated fear memory. Atropine and propranolol were injected in separate set of rats (n=6) just after the reactivation of fear memory. Short term memory and long term memory were monitored after 2 h and 24 h of reactivation respectively. Results of current study demonstrated that only atropine showed significant impairment of reconsolidation of newly formed fear memory whereas propranolol did not show fear memory disrupting effects. The results emphasize the significance of pharmacological intervention to impair reconsolidation of newly formed fear memory.