EFFECTS OF HYPOMAGNESIA ON TRANSMITTER ACTIONS IN NEOCORTICAL SLICES

被引:25
作者
ELBEHEIRY, H [1 ]
PUIL, E [1 ]
机构
[1] UNIV BRITISH COLUMBIA, FAC MED, DEPT ANAESTHESIOL, VANCOUVER V6T 1W5, BC, CANADA
关键词
D O I
10.1111/j.1476-5381.1990.tb14197.x
中图分类号
R9 [药学];
学科分类号
1007 ;
摘要
1. The effects of hypomagnesia on the neuronal responses induced by iontophoretically applied acetylcholine, glutamate, N-methylaspartate (NMDA) and γ-aminobutyric acid (GABA) were investigated using intracellular recording techniques in in vitro slices of sensorimotor cortex (guinea-pigs). 2. Perfusion with Mg-free media, with or without tetrodotoxin (TTX), induced a small hyperpolarization (~4 mV) and a small decrease (~10%) in the input resistance of neurones. During TTX-blockade of Na-spike genesis, spontaneous depolarizing waves of low frequencies were observed in neurones of slices under Mg-free conditions. 3. The effects of acetylcholine and to a lesser extent, GABA actions, were depressed in a dose-dependent, reversible manner by decreases in the [Mg2+] of the perfusing media. In neurones of slices that had been incubated in Mg-free artificial cerebrospinal fluid to ensure a maximal depletion, the responses to these transmitters were potentiated by each sequentially administered increase in extracellular [Mg2+]. The actions of NMDA were potentiated during perfusion of Mg-free media. However, the responses to glutamate, which may activate receptors for NMDA, were either depressed or unchanged under these conditions. 4. A regulatory role for external Mg cations in the responses of neocortical neurones to the transmitter substances, acetylcholine and GABA, can be inferred from these investigations which simulate hypomagnesemia. The dose-dependent depression of GABA actions by low extracellular [Mg2+] additionally provides a plausible mechanism that may contribute to the neuronal hyperexcitability that is observed during conditions of hypomagnesemia.
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页码:1006 / 1010
页数:5
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