[Simultaneous administration of ethanol emphasizes the effect of methamphetamine on central nervous system in rat...

We studied about influence of alcohol preference and of simultaneously administered ethanol (EtOH) on the effect of methamphetamine (MA) on the central nervous system neurochemically and behavioral pharmacologically using two strains of rat with high or low preference for alcohol (HAP and LAP). In the neurochemical study, we determined dopamine (DA) and serotonin (5-HT) level in striatum and nucleus accumbens (N.Acc) by means of brain microdialysis after administration of MA 1 mg/kg alone (LAP-MA group, HAP-MA group) or EtOH 2 g/kg + MA 1 mg/kg (LAP-EtOH/MA group, HAP-EtOH/MA group) every 20 minutes for 10 sessions. In the behavioral pharmacological study, we observed rat's behavior in the open field and performed scoring according to Locomotion-Stereotypy (L-S) rating scale by Ellinwood every five minutes, and counted locomotion and rearing by means of infrared beam cutting every 20 minutes after administration of MA 1 mg/kg alone (LAP-MA group, HAP-MA group) or EtOH 2 g/kg + MA 1 mg/kg (LAP-EtOH/MA group, HAP-EtOH/MA group). When MA was given alone, HAP rat showed no significant difference in locomotion, rearing and L-S score compared to LAP rat, although HAP rat showed significantly lower elevation of DA and 5-HT in both striatum and N.Acc. When EtOH was simultaneously administered with MA, in LAP rat, DA and 5-HT elevation in the striatum and N.Acc showed no significant differences between LAP-EtOH/MA group and LAP-MA group. Locomotion and rearing reduced and L-S score temporarily reduced significantly in LAP-EtOH/MA group compared to LAP-MA group. However in HAP rat, HAP-EtOH/MA group showed significantly higher DA and 5-HT elevation in both striatum and N.Acc, and also showed significantly higher L-S score and higher locomotion count compared to HAP-MA group. Our results indicate that effect of MA may be influenced by alcohol preference, and that simultaneous administration of EtOH emphasizes the effect of MA on central nervous system in rat with high alcohol preference.