Differential effects of acute administration of haloperidol and clozapine on ethanol-induced ascorbic acid release in rat striatum

Differential effects of clozapine on ethanol-induced ascorbic acid release in mouse and rat striatum

Previous studies have shown that acute systemic administration of ethanol-induced striatal ascorbic acid (AA) release in mice and rats. In the present study, in vivo brain microdialysis coupled with high performance liquid chromatography (HPLC) with electrochemical detection (ECD) was used to comparatively evaluate the effects of clozapine on ethanol-induced AA release in mouse and rat striatum. The results showed that clozapine, at the dose of 15 mg/kg i.p., had no effect on basal AA or ethanol-induced AA release in rat striatum. The potentiating effect of clozapine on ethanol-induced striatal AA release was still observed in rats, at the higher dose of 30 mg/kg. In contrast, clozapine significantly inhibited ethanol-induced AA release in mouse striatum, at the dose of 15 and 30 mg/kg, without affecting basal AA release. The present study suggested that clozapine differentially regulated ethanol-induced AA release in the mouse and rat striatum.

Effects of clozapine, olanzapine and haloperidol on ethanol-induced ascorbic acid release in mouse striatum

The effects of clozapine, olanzapine and haloperidol on ethanol-induced striatal ascorbic acid (AA) release in mice were compared by using microdialysis coupled to high performance liquid chromatography with electrochemical detection. Ethanol (4.0 g/kg i.p.) significantly stimulated striatal AA release by about 200% of baseline in mice. Clozapine and olanzapine, two atypical neuroleptic drugs, at the dose of 1.0 mg/kg s.c., had no effect on basal AA or ethanol-induced AA release. However, both drugs, at the dose of 10 mg/kg s.c., significantly inhibited ethanol-induced AA release. In contrast, haloperidol, a typical neuroleptic drug, at the doses of 0.1-2.0 mg/kg, had no effect on both basal and ethanol-induced AA release. The present study demonstrated that similar actions were exhibited by clozapine and olanzapine, but not by haloperidol, for the regulation of ethanol-induced AA release in the mouse striatum.

Endogenous released ascorbic acid suppresses ethanol-induced hydroxyl radical production in rat striatum

Previous studies have shown that acute systemic administration of ethanol induced ascorbic acid release in the striatum. However, the pharmacological implications of ethanol-induced striatal ascorbic acid release are unclear. In the present study, ethanol-induced extracellular changes of ascorbic acid and hydroxyl radical levels were detected in rat striatum by using brain microdialysis coupled to high-performance liquid chromatography with electrochemical detection. It was found that both in male and female rats, ethanol (3.0 g/kg, i.p.) increased striatal ascorbic acid release in the first 60 min after ethanol administration. Meanwhile, the extracellular hydroxyl radical levels, detected as 2,3- and 2,5-DHBA, were significantly decreased. However, when the ascorbic acid levels returned to the baseline, hydroxyl radical levels rebounded. Administration of DL-fenfluramine (20 mg/kg, i.p.) had no effect on the basal levels of ascorbic acid and hydroxyl radical, but significantly blocked ethanol-induced ascorbic acid release and increased hydroxyl radical levels significantly. Exogenous administration of ascorbic acid (20 mg/kg, s.c.) increased the extracellular levels of ascorbic acid in the striatum, and inhibited the increase of 2,3- and 2,5-DHBA in DL-fenfluramine plus ethanol group. These results provide first evidence that release of endogenous ascorbic acid in the striatum plays an important role in preventing oxidative stress by trapping hydroxyl radical in the central nervous system.

Opposite effects of sulpiride and SCH 23390 on ethanol-induced striatal ascorbic acid release in intact and 6-hydroxydopamine lesioned rats

The effects of L-sulpiride and SCH 23390 on ethanol-induced striatal ascorbic acid (AA) release in normal and 6-hydroxydopamine-lesioned rats were studied by using microdialysis coupled to high performance liquid chromatography with electrochemical detection. Ethanol (3.0 g/kg i.p.) significantly stimulated striatal AA release by 200% above the baseline in normal, 6-hydroxydopamine-lesioned, and reserpine-treated rats. L-Sulpiride, a dopamine D(2) antagonist, at the dose of 100 mg/kg i.p., decreased basal ascorbic acid release and showed an inhibitory tendency on ethanol-induced ascorbic acid release. However, at the higher dose of 200 mg/kg i.p., L-sulpiride significantly inhibited ethanol-induced ascorbic acid release in both normal and 6-hydroxydopamine-treated rats. SCH 23390, a dopamine D(1) antagonist, at the doses of 0.5 and 1.0 mg/kg i.p., potentiated ethanol-induced ascorbic acid release in normal rats. However, the potentiation of SCH 23390 on ethanol effect was not significant in 6-hydroxydopamine-treated rats at the dose of 1.0 mg/kg i.p. The present study demonstrates that opposite actions exist in the regulation of ethanol-induced ascorbic acid release in the striatum by dopamine D(1) and D(2) receptor blockade. It also suggests that the postsynaptic dopamine receptors are involved in mediation of ethanol-induced ascorbic acid release in rat striatum.