Modulation of [3H]acetylcholine release from peripheral nervous systems under in vitro conditions (nervus phrenicus of rats; small Intestine, trachea of guinea-pigs)

Wessler, Ignaz; Apel, C.; Garmsen, M.; Hellwig, D. H.; Racké, Kurt

doi:10.1016/0014-2999(90)92368-s

Cited by 1 publication

(1 citation statement)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Indeed, it is difficult to reconcile that the time course of inhibition of evoked [3H]-ACh release by tubocurarine should lag behind the occurrence of e.p.p. run-down (Wessler et al, 1987) and that abungarotoxin but not cobratoxin or erabutoxin reduced evoked [3H]-ACh release (Wessler et al, 1990).…”

Section: Discussionmentioning

confidence: 90%

Run‐down of neuromuscular transmission during repetitive nerve activity by nicotinic antagonists is not due to desensitization of the postsynaptic receptor

Hong

Chang

1991

British J Pharmacology

View full text Add to dashboard Cite

1 Whether the function of the postsynaptic acetylcholine receptor is use-dependently affected by repetitive nerve stimulation in the presence of competitive antagonists was studied in the mouse phrenic nervehemidiaphragm preparation.2 For electrophysiological experiments, the preparation was immobilized by synthetic p-conotoxin, which preferentially blocks muscular Na-channels causing neither depolarization of the membrane potential, inhibition of quantal transmitter release, nor depression of nicotinic receptor function. 3 High concentrations of cobratoxin depressed indirect twitches and endplate potentials (e.p.ps) without inducing waning of contractilities or run-down of trains of e.p.ps evoked at 10-100 Hz. However, waning and run-down were accelerated after washout of the toxin despite diminished postsynaptic receptor blockade. Once the run-down of e.p.ps was produced by washout or low concentrations of cobratoxin, further depression of e.p.p. amplitude with high concentrations of cobratoxin did not attenuate the e.p.p. rundown. 4 The degrees of waning of tetanus and trains of e.p.ps produced by a very high concentration of tubocurarine (20pM) were also less than that caused at a 100 fold lower concentration, albeit the amplitudes of twitches and the first e.p.p. were depressed more rapidly and markedly. 5 Tubocurarine, like cobratoxin, depressed the amplitude of miniature endplate potentials (m.e.p.ps) more than e.p.ps. 6 In contrast to the steepened run-down of successive e.p.ps in the presence of low concentrations of either nicotinic antagonists, the amplitude of m.e.p.ps observed during repetitive stimulation was uniform and was not different from that before stimulation. 7 The results suggest that the e.p.p. run-down and tetanic fade induced by nicotinic antagonists are due to a slow kinetic blockade of presynaptic receptors and confirm that the e.p.p. run-down is not produced by a use-dependent failure of postsynaptic nicotinic receptors. The roles of the presynaptic nicotinic receptor in positive or negative feedback modulations of transmitter release are discussed.

show abstract

Section: Discussionmentioning

confidence: 90%