The effect of glutamate and inhibitors of NMDA receptors on postdenervation decrease of membrane potential in rat diaphragm.
The early postdenervation depolarization of rat diaphragm muscle fibers (8-10 mV within 3 h in vitro) is substantially smaller (3 mV) when muscles are bathed with 1 x 10(-3) M L-glutamate (Glu) or 1 x 10(-3) M N-methyl-D-aspartate (NMDA). The effects of Glu and NMDA are inhibited in a dose-dependent manner by competitive inhibitor 2-amino-5-phosphonovaleric acid (APV) with Ki 6.3 x 10(-4) M, by 2 x 10(-7) M MK-801, which acts as an open channel inhibitor, by 2-3 x 10(-4) Zn2+, which reacts with surface-located sites of the NMDA subtype of the glutamate receptor, and also by glycine-free solutions and 7-Cl-kynurenic acid, which inhibits the glycine binding sites on NMDA receptors. It follows that the effect of glutamate on early post-denervation depolarization is mediated by the NMDA subtype of glutamate receptor with similar pharmacological properties to those found in neurons. The only exception found was the glutamate-like action of 1 x 10(-7) M MK-801, which partially prevented the early postdenervation depolarization when present in the muscle bath during the first 3 h after nerve section.
Urazaev
A Kh
AKh
Medical University, Kazan, Russia.
Naumenko
N V
NV
Poletayev
G I
GI
Nikolsky
E E
EE
Vyskocil
F
F
D000818:Animals; D003964:Diaphragm / Q000294:innervation / Q000502:physiology; D004594:Electrophysiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008839:Microelectrodes; D009121:Muscle Denervation; D018485:Muscle Fibers, Skeletal / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D015032:Zinc / Q000494:pharmacology
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D015032:Zinc