INCREASED GI-ALPHA AND GO-ALPHA MESSENGER-RNAS IN HIPPOCAMPUS AFTER REPEATED METHAMPHETAMINE ADMINISTRATION

CHANGES in transcription of Gs alpha, Gi2 alpha: and Go alpha proteins after repeated methamphetamine administration were investigated using in situ hybridization. Rats received daily injections of methamphetam ine (4 mg kg(-1)) for 14 days. Four hours after the last injection, Go alpha mRNA showed an increase of 16.6-31.6% in CA1, CA3 and dentate g yrus of the hippocampus. Gi alpha mRNA level increased by 24.2% in CA1 , while Gs alpha mRNA remained unaffected. Go alpha and Gi alpha mRNA returned to basal levels after 48 h abstinence. The expression of thes e G alpha mRNA in other brain regions, including substantia nigra, ven tral tegmentum area, striatum, accumbens and cortices, was unchanged. The increase in Go alpha and Gi alpha mRNAs restricted only to the hip pocampus after repeated methamphetamine administration may be involved in the development of dependence rather than behavioral sensitization .