Brain catecholamines, serotonin and their metabolites in mice selected for low (MGL) and high (MGH) blood magnesium levels.

Brain noradrenaline, dopamine, DOPAC (3-4 dihydroxyphenylacetic acid), HVA (homovanillic acid), serotonin and 5-HIAA (5-hydroxyindolacetic acid) were determined by high performance liquid chromatography with amperimetric detection in adult male mice from three different strains : mice with genetically low (MGL) or high (MGH) blood magnesium levels, obtained by selective breeding and outbred Swiss albino mice. Noradrenaline levels were significantly higher (P < or = 0.001) in MGL than in MGH and Swiss mice : DOPAC levels were lower (P < or = 0.001) in MGL than in MGH and Swiss. Little or no differences were found for these variables between MGH and Swiss mice. MGL and MGH animals had similar brain dopamine, HVA and serotonin contents. These results suggest that the mere selection for genetic traits inducing low blood magnesium levels increases the synthesis of noradrenaline or decreases its catabolism. The above data together with the higher urinary noradrenalin excretion previously observed in the MGL line might account for the higher sensitivity and/or reactivity of MGL animals to stress. Swiss mice had significantly lower (P < or = 0.001) brain dopamine and serotonin contents than both MGL and MGH lines; indeed Swiss mice and MGL/MGH mice were issued from very different populations and had vastly different stocks of genes. Brain 5-HIAA content was also found higher (P < or = 0.01) in MGH than in MGL and Swiss mice; this latter result needs to be confirmed by further research.