Responses to the Lowering of Magnesium and Calcium Concentrations in the Cerebrospinal Fluid of Unanaesthetized Sheep

Abstract

A technique for ventriculolumbar perfusion of the cerebrospinal fluid space has been used to study the neuromuscular effects of low concentrations of magnesium and calcium in the cerebrospinal fluid of conscious sheep. Perfusion with synthetic cerebrospinal fluid solutions containing less than O' 6 mg magnesium/lOO ml produced episodes of tetany which were abolished by perfusion with a solution of normal magnesium concentration. This suggests that the low cerebrospinal fluid magnesium concentrations reported in cases of hypomagneseamic tetany may result in changes within the central nervous system that could produce the nervous signs. Perfusates with a calcium concentration below 2·0 mg/lOO rnl caused hyperpnoea and continuous muscle tremors. Magnesium (0' 6 mg/lOO m!) and calcium (2·0 mg/lOO ml) perfused simultaneously acted synergistically to produce signs characteristic of low levels of each of the ions.