Effects of manganese ions in the neuromuscular junction

RESUMO

The neurotoxic effects of manganese occured mainly from its inhalation are well described in the literature. In this study we have been demonstrated the potent and reversible effect of manganese ions (Mn²+) on neuromuscular transmission using conventional myographic. The Mn²+ mechanism wich causes reversible blockade at neuromuscular junction was investigated in isolated mouse phrenic nerve-diaphragm (PND) preparations. As much Mn²+ 0.9 mM as Mn²+ 1.8 mM produced rapid neuromuscular blockade (50% in < 4 min), but only the lower concentration reversed spontaneously. The use of d-tubocurarine (5.8 µM), 3,4-diaminopyridine 3,4-DAP, 0.09 mM) and dantrolene (10 µM) excluded the involvment of nicotinic receptors, K+ channels and ryanodine receptors, respectively, as the potential target for this ion. Manganese acts an early competitive antagonist and after as an agonist of Ca²+, indicating that this ion may probably act via Ca²+ cannels...