Regional brain monoamine concentrations and their alterations in bovine hypomagnesaemic tetany experimentally induced by a magnesium-deficient diet

Monoamines are important brain neurotransmitters. An investigation was carr ied out to determine if hypomagnesaemic tetany was associated with alterati ons in regional brain monoamine concentrations in bovines. The results, est ablished in cows with normal magnesium status, demonstrated that regional d ifferences existed in the distribution and concentration of brain monoamine s in the adult bovine, which were similar to those in other species. In mag nesium-deficient cows, severe hypomagnesaemia and lowered cerebrospinal flu id (CSF) magnesium concentrations were associated with significant alterati ons in monoamine concentrations in some brain regions. Alterations in 3,4-d ihydroxyphenylalanine (DOPA) and dihydroxyphenylacetic acid (DOPAC) concent rations in the corpus striatum, and dopamine (DA) in the cerebral cortex an d cerebellum were recorded. These regions play an important role in both vo luntary and involuntary motor function, and therefore these alterations may play a role in the aetiology of hypomagnesaemic tetany. However, there was no significant change in DA concentrations in the corpus striatum (the mai n dopaminergic region in the brain) associated with hypomagnesaemia. In add ition, a significantly lower norepinephrine (NE) concentration in the corpu s striatum of hypomagnesaemic animals was also recorded. Norephinephrine is generally excitatory and therefore lowered NE concentrations would be expe cted to result in depression rather than stimulation of motor function. (C) 2000 Harcourt Publishers Ltd.