VULNERABILITY OF SYNAPTIC PLASTICITY IN THE STRIATUM OF METHAMPHETAMINE-SENSITIZED RATS

We examined the influence of ischemia on methamphetamine (MAP)-induced behavioral sensitization and enhancement of dopamine (DA) release. Af ter the recovery period of the ischemia operation, rats were treated w ith MAP (1 mg/kg, i.p.) once daily for 6 consecutive days. Re-administ ration of MAP (0.5 mg/kg, i.p.) potentiated the increase of locomotor activity after a 3-day withdrawal and the enhancement of DA release fr om striatal slices after a 6-day withdrawal. The MAP-induced sensitiza tion was impaired by 5 min ischemia. On the other hand, the increase o f locomotor activity induced by single MAP (1 mg/kg, i.p.) administrat ion was impaired by 20 min of ischemia. Moreover, in saline-treated ra ts the increase of DA release from striatal slices induced by MAP (10 mu M) application was also impaired by 20 min of ischemia. These resul ts indicate that the neuronal plastic change may be very vulnerable to ischemia in MAP-induced sensitization.