Acetylcholine-activated chloride channels produce an inhibitory junction potential in buccal muscle cells of
            Aplysia

Intracellular recordings were made from the circular smooth muscle cells of the canine jejunum to study the effect of exogenous ATP and to compare the ATP response to the nonadrenergic, noncholinergic (NANC) inhibitory junction potential (IJP) evoked by electrical field stimulation (EFS). Under NANC conditions, exogenous ATP evoked a transient hyperpolarization (6.5 ± 0.6 mV) and EFS evoked a NANC IJP (17 ± 0.4 mV). ω-Conotoxin GVIA (100 nM) and a low-Ca2+, high-Mg2+ solution abolished the NANC IJP but had no effect on the ATP-evoked hyperpolarization. The ATP-evoked hyperpolarization and the NANC IJP were abolished by apamin (1 μM) and N G-nitro-l-arginine (100 μM). Oxyhemoglobin (5 μM) partially (38.8 ± 5.5%) reduced the amplitude of the NANC IJP but had no effect on the ATP-evoked hyperpolarization. Neither the NANC IJP nor the ATP-evoked hyperpolarization was affected by P2 receptor antagonists or agonists, including suramin, reactive blue 2, 1-( N, O-bis-[5-isoquinolinesulfonyl]- N-methyl-l-tyrosyl)-4-phenylpiperazine, pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid, α,β-methylene ATP, 2-methylthioadenosine 5′-triphosphate tetrasodium salt, and adenosine 5′- O-2-thiodiphosphate. The data suggest that ATP evoked an apamin-sensitive hyperpolarization in circular smooth muscle cells of the canine jejunum via local production of NO in a postsynaptic target cell.

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Can nonadrenergic inhibitory varicosities be Identified structurally

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y77-035 ◽

1977 ◽

Vol 55 (2) ◽

pp. 243-250 ◽

Cited By ~ 33

Author(s):

E. E. Daniel ◽

G. S. Taylor ◽

V. P. Daniel ◽

M. E. Holman

Keyword(s):

Small Proportion ◽

Longitudinal Muscle ◽

Circular Muscle ◽

Muscle Cells ◽

Muscle Layer ◽

Intrinsic Nerves ◽

Inhibitory Junction Potential ◽

Rabbit Jejunum ◽

Junction Potential ◽

Stimulation Of

The distribution of vesicles in axon varicosities was examined in rabbit jejunum and opossum esophagus. Circular muscle cells of both rabbit jejunum and opossum esophagus responded to stimulation of intrinsic nerves with inhibitory junction potential in nearly all cases. Inhibitory junction potentials were rare and small in longitudinal muscle cells of rabbit jejunum. There were few axon varicosities with a predominance of large opaque vesicles or large dense-cored vesicles in any muscle layer of rabbit or opossum or in the plexuses of rabbit jejunum. There were almost as high a proportion of such varicosities in longitudinal as in circular muscle of rabbit jejunum, and there were almost none in circular muscle of opossum esophagus. The distribution of vesicles in varicosities was found often to be heterogeneous and could account for the observed occurrence of a small proportion of varicosities with a predominance of large vesicles. It is suggested that there is no structural distinction in vertebrates between axons which are cholinergic and axons which are nonadrenergic inhibitory.

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