AMPHETAMINE SENSITIZATION AUGMENTS AMPHETAMINE-INDUCED FOS EXPRESSIONIN THE LATERAL HABENULA

Repeated amphetamine (AMPH) administration results in behavioral sensi tization. To investigate the neuroanatomical basis of this phenomenon, we examined the effects of AMPH sensitization on AMPH-induced Fos exp ression in 24 regions of the rat brain. Rats received repeated injecti ons of AMPH (4 mg/kg, intraperitoneally, once every other day, eight t imes in total) or saline (same schedule as for AMPH). After a 14-day d rug abstinence period, rats were challenged with 2 mg/kg AMPH intraper itoneally. As measured by Fos immunohistochemistry, the AMPH sensitiza tion procedure enhanced subsequent AMPH-induced Fos expression in only one structure, the medial part of the lateral habenula. These results indicate that AMPH-induced behavioral sensitization is not accompanie d by widespread increases in the ability of AMPH to increase regional Fos expression in the forebrain. The lateral habenula appears to be in volved in the possible neural framework that is responsible for the ex pression of behavioral sensitization. (C) 1997 Elsevier Science B.V.