The effects of glutamate on spontaneous acetylcholine secretion processes in the rat neuromuscular synapse.
Experiments on rat diaphragm muscles showed that glutamate (10 microM-1 mM) had no effect on the mean frequency, interspike intervals, and amplitude-time characteristics of miniature endplate potentials, but had a suppressive action on non-quantum secretion (the intensity of which was assessed in terms of the H effect). The effect of glutamate was markedly concentration-dependent and was completely overcome by blockade of NMDA receptors, inhibition of NO synthase, and by binding of NO molecules in the extracellular space by hemoglobin. It is suggested that glutamate can modulate the non-quantum release of acetylcholine, initiating the synthesis of NO molecules in muscle fibers via activation of NMDA receptors followed by the retrograde action of NO on nerve terminals.
Malomuzh
A I
AI
Kazan' Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, 420503 Kazan', Russia.
Mukhtarov
M R
MR
Urazaev
A Kh
AKh
Nikol'skii
E E
EE
Vyskochil
F
F
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018846:Excitatory Amino Acids / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D009045:Motor Endplate / Q000187:drug effects / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000378:metabolism*; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D052248:Nitric Oxide Synthase Type I; D051381:Rats
D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D018846:Excitatory Amino Acids; D009569:Nitric Oxide; D018698:Glutamic Acid; D016291:Dizocilpine Maleate; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester