Influence of 6-hydroxydopamine on ethanol narcosis in mice

The effects of 6-hydroxydopamine (6-OHDA) i.c.v. on ethanol-induced narcosis were studied in mice, either untreated or pretreated with alpha-methyl-p-tyrosine (AMPT), p-chlorophenylalanine (PCPA) or 5-hydroxytryptophan (5-HTP). Mice treated with 6-OHDA 200 micrograms i.c.v., exhibited longer ethanol narcosis time than untreated controls. This effect was significantly increased when mice treated with 6-OHDA received AMPT (inhibitor of catecholamine biosynthesis) or 5-HTP (precursor or serotonin biosynthesis). After administration of PCPA (inhibitor of tryptophan hydroxylase) 6-OHDA did not prolong ethanol narcosis. Alcohol blood levels at awakening time were not significantly influenced by 6-OHDA. These results are consistent with the idea that a decrease in brain noradrenaline as well as an increase in brain serotonin enhance the narcotic action of ethanol, while both, the increase in brain noradrenaline and the decrease in brain serotonin shorten ethanol narcosis.