AMPHETAMINE SENSITIZATION ENHANCES REGIONAL C-FOS EXPRESSION PRODUCEDBY CONDITIONED FEAR

Chronically administered amphetamine can result in a paranoid psychosi s that can be re-induced in former amphetamine abusers by psychologica l stressors. In an attempt to investigate the neurobiological correlat es of this phenomenon, the present study examined the effects of prior D-amphetamine sensitization on regional c-fos expression induced by a psychological stressor. Rats received intermittent footshock in a dis tinctive environment for 30 min/day for three days. Three days after t he last fear conditioning session, the animals received injections of saline or D-amphetamine (4 mg/kg, i.p.) once every second day for 16 d ays (eight injections in total). After a iii-day drug abstinent period , the animals were placed in the fear conditioning apparatus but witho ut footshock. The amphetamine sensitization procedure significantly en hanced the effects of conditioned fear on c-Sos expression in several brain regions. These included the cingulate cortex area 3, agranular i nsular cortex (layers 2 and 3), claustrum, piriform cortex, the shell region of the nucleus accumbens, medial striatum, ventral lateral sept um, and CA3 and polymorphic layer of the hippocampal formation. These results indicate that D-amphetamine sensitization can have long-lastin g effects on the neural circuitries activated by conditioned stressors . Copyright (C) 1996 IBRO. Published by Elsevier Science Ltd.