Regional catecholamine levels in brains of normal and ethanol-tolerant long-sleep and short-sleep mice

The objective of this study was to further investigate neurochemicals which might modulate congenital differences in sensitivity to the acute and chronic effects of ethanol. Catecholamine levels were measured in the cortex, hippocampus, midbrain and cerebellum of long-sleep (LS) and short-sleep (SS) mice. These measurements revealed that norepinephrine (NE) levels were equivalent in all these brain regions of both strains except for a significantly greater concentration in the midbrain of LS mice. The hippocampus, cortex and cerebellum of SS mice contained more epinephrine (E) than for LS mice. Likewise, the hippocampus and cerebellum of SS mice had higher levels of dopamine (DA), while in the midbrain this amine was more abundant in LS mice. Following 7–10 days of ethanol ingestion, both LS and SS mice exhibited a significant reduction in the duration of ethanol-induced loss of righting reflex. This tolerant state was associated with a depletion of NE in the hippocampus and cortex of both strains. NE was also significantly reduced in the midbrain of LS and the cerebellum of SS mice. On the other hand, E levels were unaltered except for a reduction in the hippocampus of tolerant SS mice. DA levels declined in all brain regions of tolerant mice except for the cerebellum of LS mice and the midbrain of SS mice where a significant increase and no change in DA concentration was detected, respectively. Interestingly, the brain levels of 3-methoxy-4-hydroxyphenylglycol were uniformly increased during the tolerant state for both strains. This suggests that the generalized reduction of brain catecholamines during the tolerant state is secondary to an enhanced activity of the neuronal pathways which these chemicals mediate.