SCOPOLAMINE SELECTIVELY DISRUPTS THE ACQUISITION OF CONTEXTUAL FEAR CONDITIONING IN RATS

Muscarinic cholinergic antagonism produces learning and memory deficit s in a variety of hippocampal-dependent tasks. Hippocampal lesions pro duce both acquisition deficits and retrograde amnesia for contextual f ear conditioning, but do not impact fear conditioning to discrete cues . In order to examine the effects of muscarinic antagonism in this par adigm, rats were given scopolamine (1 mg/kg) either before or for 3 da ys after a Pavlovian fear-conditioning session in which tones were pai red with aversive footshocks. Fear to the context and the tone was ass essed by measuring freezing in separate tests. It was found that pretr aining, but not posttraining, scopolamine severely impaired contextual fear conditioning; tone conditioning was not affected under either co ndition. (C) 1995 Academic Press, Inc.