Effect of GABAergic Compounds on the Anion-Sensitive Mg²⁺-ATPase from Bream (Abramis brama L.) Brain

S. A. Menzikov^* and O. V. Menzikova

Papanin Institute of Biology of Inland Waters, Russian Academy of Sciences, Borok, Yaroslavl Region, 152742 Russia; fax: (085) 225-3845; E-mail: sam@ibiw.yaroslavl.ru

^* To whom correspondence should be addressed.

Received July 29, 1999; Revision received October 27, 1999

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Preincubation of plasma membranes from bream brain with 10^-8-10^-4 M gamma-aminobutyric acid (GABA) or muscimol increased the anion-sensitive Mg²⁺-ATPase activity. The activating effect of neurotransmitters on the Mg²⁺-ATPase is enhanced with increasing preincubation time of the membranes with the ligands, decreases with increasing Mg²⁺-ATP concentration in the incubation medium, and is inhibited in the presence of the GABA_a-receptor antagonist, bicuculline (90 µM). The anions Cl^-, Br^-, and I^- stimulate the basal Mg²⁺-ATPase activity, and an effect of 10^-4 M GABAin the presence of anions was not found. It is supposed that GABAergic ñhemicals modify the anion-sensitive Mg²⁺-ATPase in a receptor-dependent way.

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KEY WORDS: fish, brain, bream, plasma membranes, Mg²⁺-ATPase, anions, GABA, muscimol, bicuculline

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