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A study of excitatory neuromuscular transmission in the bovine trachea
Author(s) -
Cameron A. R.,
Kirkpatrick C. T.
Publication year - 1977
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1977.sp011979
Subject(s) - excitatory postsynaptic potential , depolarization , acetylcholine , axon , neuromuscular junction , stimulation , contraction (grammar) , anatomy , neuromuscular transmission , biophysics , chemistry , muscle contraction , biology , neuroscience , endocrinology , inhibitory postsynaptic potential
1. The excitatory innervation of bovine tracheal smooth muscle has been studied with the sucrose‐gap apparatus. 2. Single 2 ms electrical stimuli applied to the whole tissue excited intrinsic nerves, and produced a small transient depolarization of the smooth muscle, the excitatory junction potential (e.j.p.). The e.j.p. caused a twitch‐type contraction; twitches and e.j.p.s summated during repetitive stimulation but facilitation was not observed, and action potentials were never elicited. 3. The effects of electrical stimulation could be abolished by atropine (5 × 10 −7 mol/l) and augmented by neostigmine (4 × 10 −6 mol/l), and were mimicked by exogenous acetylcholine (1·0 μg/ml). 4. With the electron microscope, the density of innervation was found to be low (one axon per ninety smooth muscle cells). Axons were found in small groups in the clefts between bundles of cells, but no axons penetrated within the muscle bundles. Naked axon varicosities containing agranular vesicles were seen, but no axon approached within 200 nm of a smooth muscle cell. 5. It is difficult to reconcile the sparsity of innervation with the dependence of the tissue on nerve excitation to initiate activity.