نظرات ياداشت سمي ترين موجودات جهان - طب اورژانس دكتر رحمت سخني Dr.Rahmat Sokhani

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Extracellular Mg²⁺ modulates intracellular Ca²⁺ in acutely isolated hippocampal CAI pyramidal cells of the guinea-pig

Aimin Zhang^a, Shou-Hui Fan^b, Toni P.-O. Cheng^c, Bella T. Altura^a^,^e, Robert K.S. Wong^b and Burton M. Altura^,^a^,^d^,^e

^aDepartment of Physiology, Box 31, State University of New York, Health Science Center at Brooklyn, 450 Clarkson Ave., Brooklyn, NY 11203, USA

^bDepartment of Pharmacology, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203, USA

^cDepartment of Anatomy and Cell Biology, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203, USA

^dDepartment of Medicine, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203, USA

^eCenter for Cardiovascular and Muscle Research, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203, USA

Accepted 26 March 1996.

Available online 12 September 2003.

Abstract

Using digital imaging microscopy and fluorescent probes, isolated hippocampal CAI pyramidal neurons of the guinea-pig were used to examine the roles of [Mg²⁺]_o in regulation of [Ca²⁺]_i and [Mg²⁺]_i. Low extracellular Mg ([Mg²⁺]_o) (0.3 mM) significantly increased [Ca²⁺]_i compared to 1.2 and 4.8 MM [Mg²⁺]_o. In contrast, [Mg²⁺]_i levels remained relatively constant, irrespective of alterations of [Mg²⁺]_o. The sustained rise in [Ca²⁺]_i induced by low [Mg²⁺]_o was reduced 70% by 1 ?M verapamil and 42%v by 1 mM Ni²⁺, and completely abolished by 5 mM Ni²⁺. The data suggest that [Mg²⁺]_o regulates [Ca²⁺]_i in hippocampal neurons, probably by modulating Ca²⁺ entry via voltage-sensitive Ca²⁺ channels, which may play important roles in epileptogenesis, memory, learning and brain trauma. Furthermore, the results demonstrate that intracellular Mg²⁺ concentration does not follow passively the concentration of Mg²⁺ in the extracellular solution.

Keywords: Intracellular Ca²⁺; Intracellular Mg²⁺; Voltage-sensitive calcium channel; Hippocampal neuron; Digital imaging microscopy