Effects of repeated methamphetamine administration on dopamine D1 receptor, D2 receptor and adenylate cyclase type V mRNA levels in the rat striatum.

Dopamine D1 receptor (D1R), D2 receptor (D2R) and adenylate cyclase type V (AC5) mRNAs in the rat dorsal striatum (CPu) and ventral striatum (Acb) were measured by in situ hybridization histochemistry (ISHH) after repeated methamphetamine (MAP) administration. MAP (4 mg/kg) or an equivalent volume of saline was administered intraperitoneally once daily for 10 days to male Wistar rats. After 7 days of abstinence, behavioral experiment with MAP-challenge revealed that a significant behavioral sensitization was achieved in MAP-treated animals. The animals were sacrificed 7 days after the last injection and brain sections were analyzed by ISHH using 35S-labeled antisense oligonucleotide probes. We found that D1R mRNA levels in the CPu were significantly increased (124% of control, P < 0.01). In contrast, repeated MAP-treatment did not significantly affect the expression of D1R mRNA in Acb or mRNA for D2R or AC5. It was concluded that MAP-induced behavioral sensitization is accompanied by increased D1R mRNA levels in CPu.