Brain weight and noradrenaline content in mice selected for low (MGL) and high (MGH) blood magnesium

Brain noradrenaline content was determined by high performance liquid chromatography in adult male mice from three different strains: 40 mice with genetically low (MGL) or high (MGH) blood magnesium levels, obtained by selective breeding and 20 outbred Swiss albino mice. Brain wet weight and noradrenaline levels were significantly higher in MGL than in MGH and Swiss mice. Few or no differences were found between MGH and Swiss mice. MGL and MGH animals had a similar mean body weight, were raised in identical conditions, and were fed with a normal diet, rich in magnesium. These results together with the higher urinary noradrenaline excretion previously observed in the MGL line, indicate that the mere selection for genetic traits inducing low blood magnesium levels entails an increased catecholamine production. This phenomenon most probably accounts for the higher sensitivity and/or reactivity of MGL animals to stress. The possible role of magnesium-controlling genetic factors in the regulation of brain growth is also suggested.