Dexmedetomidine attenuates the enhancement effect of propofol on conditioned fear memory in rats

Abstract

Abstract Objective Posttraumatic stress disorder (PTSD) is a frequent and disabling consequence of traumatic events. A previous study found that dexmedetomidine can alleviate anxiety like behavior and cognitive impairment in PTSD model rats. The aim of this study was to investigate the the effects of dexmedetomidine on the dosage and time window of conditioned fear memory enhanced by propofol in rats. Methods After conditioned fear training and propofol injection, the proportion of freezing time in rats with different doses and timing by dexmedetomidine were evaluated. We also examined The activation of excitatory and inhibitory neurons in the basolateral amygdala (BLA) by dual-labeling immunofluorescence. Results Propofol heightened the freezing time in the context fear conditioning test. After propofol injection, the fluorescence intensity of c-Fos in dual-localization with CaMKⅡ increased and the fluorescence intensity of c-Fos in dual-localization with GAD67 declined in the basolateral amygdala (BLA). The use of medium or high concentration of dexmedetomidine reduced the freezing time of rats injected with propofol, so did the immediate and early use. However, high concentration of dexmedetomidine significantly increased respiratory depression. After giving dexmedetomidine to rats rejected with propofol, the fluorescence intensity of c-Fos in dual-localization with CaMKⅡ declined and the fluorescence intensity of c-Fos in dual-localization with GAD67 increased in the BLA. Conclusion Dexmedetomidine can attenuate the enhancement effect of propofol on conditioned fear memory in rats, and the best effect is achieved by early administration of moderate dose (20µg/kg) (within 30 min after propofol administration).