RELATIONSHIP BETWEEN MEMORY AND FEAR - DEVELOPMENTAL AND PHARMACOLOGICAL STUDIES

Habituation of the acoustic startle response (ASR) and freezing respon ses were assessed simultaneously in rats of different ages. Results sh owed that until 30 days of age rats were not able to express long-term habituation of the ASR, whereas irrespective of age, all rats exhibit ed the increased freezing responses as a result of fear conditioning. In addition, the interaction between fear and memory was studied using the same behavioral model in adult rats treated intraperitoneally wit h diazepam at doses 1.2 and 2.5 mg/kg. Diazepam administration did not result in a significant change in initial startle responsiveness but elicited a profound suppression of startle amplitude over trials. Furt hermore, animals given diazepam showed more initial freezing than the vehicle-treated controls, while fear-conditioned freezing was decrease d by diazepam. The pattern of results is discussed in relation to deve lopmental and pharmacological dissociations between the different beha vioral components of responses to aversive and stressful cues.