Amphetamine sensitization enhances regional c-fos expression produced by conditioned fear.
Chronically administered amphetamine can result in a paranoid psychosis that can be re-induced in former amphetamine abusers by psychological stressors. In an attempt to investigate the neurobiological correlates 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 distinctive environment for 30 min/day for three days. Three days after the last fear conditioning session, the animals received injections of saline or D-amphetamine (4 mg/kg, i.p.) once every second day for 16 days (eight injections in total). After a 14-day drug abstinent period, the animals were placed in the fear conditioning apparatus but without footshock. The amphetamine sensitization procedure significantly enhanced the effects of conditioned fear on c-fos expression in several brain regions. These included the cingulate cortex area 3, agranular insular cortex (layers 2 and 3), claustrum, piriform cortex, the shell region of the nucleus accumbens, medial striatum, ventral lateral septum, and CA3 and polymorphic layer of the hippocampal formation. These results indicate that D-amphetamine sensitization can have long-lasting effects on the neural circuitries activated by conditioned stressors.
Hamamura
T
T
Department of Psychiatry, University of British Columbia, Vancouver, Canada.
Ichimaru
Y
Y
Fibiger
H C
HC
D000818:Animals; D001923:Brain Chemistry / Q000502:physiology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003913:Dextroamphetamine / Q000494:pharmacology*; D004597:Electroshock; D005239:Fear / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D013268:Stimulation, Chemical; D013315:Stress, Psychological / Q000378:metabolism / Q000503:physiopathology
D000697:Central Nervous System Stimulants; D016760:Proto-Oncogene Proteins c-fos; D003913:Dextroamphetamine