Evidence that catecholamines increase acetylcholine release from neuromuscular junction through stimulation of alpha-1 adrenoceptors

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1. The effects of alpha-1 adrenoceptor agonists on 3H-acetylcholine release from mouse phrenic nerve-hemidiaphragm preparation were studied. 2. In preparation which had been incubated with 3H-choline, electrical stimulation (50 Hz, 0.8 s trains every 10 s) released 3H-acetylcholine. Neurochemical evidence was obtained that noradrenaline, adrenaline and phenylephrine facilitated the stimulation evoked release of 3H-acetylcholine. This effect was much more marked when the prejunctional nicotinic receptors mediating positive feedback modulation were blocked by (+)-tubocurarine. In the presence of this drug, when the release of 3H-acetylcholine was reduced, alpha-1 adrenoceptor agonists enhanced the release in a prazosin-sensitive manner. 3. The rank order of potency of alpha-1 adrenoceptor agonists was adrenaline > noradrenaline > phenylephrine. By contrast, methoxamine had no effect on the release of 3H-acetylcholine. It is suggested, therefore, that circulating catecholamines may be able to affect neuromuscular transmission through stimulation of presynaptic alpha-1 adrenoceptors.

Original languageEnglish
Pages (from-to)435-438
Number of pages4
JournalNaunyn-Schmiedeberg's Archives of Pharmacology
Issue number5
Publication statusPublished - May 1 1991



  • Neuromuscular junction
  • acetylcholine release
  • alpha-1 adrenoceptor

ASJC Scopus subject areas

  • Pharmacology

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