Abstract
Using nerve-muscle preparations of the cutaneous pectoris muscle of the frog, and recording extracellular evoked electrical responses from a nerve ending (NE), we have studied the mechanisms by which exogenic acetylcholine (ACh) influences the ion currents of a motor nerve ending. We have established that ACh in concentrations of 0.1–0.6 mmoles/liter causes an increase in the third phase of the NE response, and in concentrations of 0.7–2.0 mmoles/liter, suppresses it. We have found that tubocurarine and atropine do not block the effects of ACh. It has been shown that the ACh-induced increase in the amplitude of the third phase of the NE response is seen against a background of calcium channel blockers, and it can be eliminated by 4-aminopyridine (4-AP) and tetraethylammonium. The inhibitory effect of ACh on the third phase of the NE response is not present in calcium-free solutions, nor when the calcium current is blocked. A discussion is given of the mechanisms of exogenic and endogenic ACh action on the potential-dependent and calcium-activated potassium current of the NE.
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Literature cited
A. L. Zefirov, E. E. Nikol'skii, and D. M. Shakir'yanova, "The action of exogenic acetylcholine and cholinomimetics on the ion current of a motor nerve ending of the frog," in: The Physiology of Transmitters. The Peripheral Synapse, Abstract of Report at VI All-Union Symposium, Kazan (1991), p. 47.
A. L. Zefirov and I. A. Khalilov, "Ion currents of a nerve ending in the tailor's muscle of the frog," Neirofiziologiya,15, No. 6, 770–779 (1985).
A. L. Zefirov, I. A. Khalilov, and Kh. S. Khamitov, "Calcium and calcium-activated potassium currents of a motor nerve ending of the frog," ibid.,19, No. 4, 457–472 (1987).
D. A. Brown, B. H. Gahwhiler, W. H. Griffith, and J. V. Halliwell, "Membrane currents in hippocampal neurons," Progr. Brain Res.,83, 141–160 (1990).
D. Colquhoun and D. C. Ogden, "Evidence from single-channel recording of channel block by nicotinic agonists at the frog neuromuscular junction," J. Physiol.,353, 90 (1984).
B. Katz, "Looking back at the neuromuscular junction," in: Neuromuscular Junction, Amsterdam (1989), pp. 3–9.
J. Kehoe, "Acetylcholine receptors on molluscan neurones," Adv. Pharmacol. Therap.,8, 285–298 (1979).
R. Latorre, A. Obernauser, P. Labarca, and O. Alvarez, "Varieties of calcium-activated potassium channels," Annu. Rev. Physiol.,51, 385–399 (1989).
I. B. Levitan, "Modulation of ion channels in neurons and other cells," Annu. Rev. Neurosci.,11, 119–136 (1988).
A. Mallart, "Presynaptic currents in frog motor endings," Pflugers Arch.,400, No. 1, 8–13 (1984).
Y. Nakajima, S. Nakajima, R. J. Leonard, and K. Yamagichi, "Acetylcholine raises excitability by inhibiting the fast transient potassium currents in cultured rats sympathetic neurons," Proc. Natl. Acad. Sci. USA,83, No. 4, 3022–3026 (1986).
S. M. Sine and J. N. Steinback, "Activation of a nicotinic acetylcholine receptor," Biophys. J.,45, No. 2, 175–185 (1984).
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S. V. Kurashov Medical Institute, Ministry of Health of the Russian Federation, Kazan. Translated from Neirofiziologiya, Vol. 24, No. 6, pp. 678–683, November–December, 1992.
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Zefirov, A.L., Shakir'yanova, D.M. Action of exogenic acetylcholine on the potassium currents of frog motor nerve endings. Neurophysiology 24, 454–458 (1992). https://doi.org/10.1007/BF01052964
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DOI: https://doi.org/10.1007/BF01052964