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Prejunctional actions of N-ethyl-maleimide and phenoxybenzamine in rat vas deferens

I Browne1, G Thomas, K Gavin

  • 1Department of Physiology, Royal College of Surgeons, Ireland, Dublin.

European Journal of Pharmacology
|November 24, 1994
PubMed

Insights

N-ethyl-maleimide affects prejunctional receptors in rat vas deferens by mechanisms beyond G-protein inactivation, as shown by its distinct effects compared to alpha 2-adrenoceptor antagonists.

Area of Science:

  • Pharmacology
  • Neuroscience
  • Physiology

Background:

  • Prejunctional receptors modulate neurotransmitter release.
  • Alpha-2 adrenoceptors and serotonin receptors play roles in regulating smooth muscle contraction.
  • N-ethyl-maleimide is a chemical agent used to probe protein function.

Purpose of the Study:

  • To investigate the mechanism of action of N-ethyl-maleimide on prejunctional inhibitory receptors.
  • To differentiate the effects of N-ethyl-maleimide from known alpha-2 adrenoceptor antagonists.

Main Methods:

  • Electrically evoked isometric contractions of rat vas deferens.
  • Pretreatment with N-ethyl-maleimide, phenoxybenzamine, or EEDQ.
  • Receptor binding assays using [3H]MK 912.

Main Results:

  • N-ethyl-maleimide reduced the potency of xylazine and 5-hydroxytryptamine but not amidephrine.
  • Phenoxybenzamine and EEDQ altered xylazine's effects, but N-ethyl-maleimide did not further modify these.
  • N-ethyl-maleimide did not bind to alpha-2 adrenoceptors at effective concentrations.

Conclusions:

  • N-ethyl-maleimide's effects on prejunctional receptors may involve mechanisms other than direct G-protein inactivation.
  • The findings suggest a complex interplay between N-ethyl-maleimide, G-proteins, and alpha-2 adrenoceptors.

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