Modulation of neurotransmitter release by opioid mu- and kappa-receptors from adrenergic terminals in the myenteric plexus of the guinea-pig colon: effect of alpha 2-autoreceptor blockade

Neurosci Lett. 1997 Jan 31;222(2):75-8. doi: 10.1016/s0304-3940(97)13344-4.

Abstract

We have studied the effect of [D-Ala2,N-Me-Phe4,Gly-ol5]-enkephalin (DAMGO, opioid mu-receptor agonist) and ICI-204,448 (kappa-receptor agonist) on endogenous noradrenaline release in the guinea-pig isolated distal colon. DAMGO enhances noradrenaline over-flow and this effect is antagonized by naloxone (pIC50 = 10.27) and nor-binaltorphimine (pIC50 = 7.97), and concentration-dependently turned into inhibition by yohimbine. ICI-204,448 inhibits noradrenaline overflow and is antagonized by naloxone (pIC50 = 9.38) and nor-binaltorphimine (pIC50 = 10.48), but is not affected by yohimbine. Evidence is thus given that mu- and kappa-opioid receptors modulate noradrenaline release in the guinea-pig colon. Modifications by yohimbine of the effect of DAMGO indicate the existence of a functional relationship between mu-receptors and alpha(2)-autoreceptors in this model.

MeSH terms

  • Adrenergic alpha-2 Receptor Antagonists
  • Adrenergic alpha-Agonists / metabolism
  • Adrenergic alpha-Agonists / pharmacology
  • Adrenergic alpha-Antagonists / pharmacology*
  • Analgesics / pharmacology
  • Animals
  • Colon / innervation
  • Dose-Response Relationship, Drug
  • Electric Stimulation
  • Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
  • Enkephalins / pharmacology
  • Guinea Pigs
  • Myenteric Plexus / chemistry*
  • Myenteric Plexus / drug effects
  • Myenteric Plexus / metabolism
  • Naloxone / pharmacology
  • Naltrexone / analogs & derivatives
  • Naltrexone / pharmacology
  • Narcotic Antagonists / pharmacology
  • Neurotransmitter Agents / metabolism
  • Norepinephrine / metabolism
  • Norepinephrine / pharmacology
  • Pyrrolidines / pharmacology
  • Receptors, Adrenergic, alpha-2 / metabolism*
  • Receptors, Opioid, kappa / agonists
  • Receptors, Opioid, kappa / antagonists & inhibitors
  • Receptors, Opioid, kappa / metabolism*
  • Receptors, Opioid, mu / agonists
  • Receptors, Opioid, mu / antagonists & inhibitors
  • Receptors, Opioid, mu / metabolism*
  • Yohimbine / pharmacology

Substances

  • Adrenergic alpha-2 Receptor Antagonists
  • Adrenergic alpha-Agonists
  • Adrenergic alpha-Antagonists
  • Analgesics
  • Enkephalins
  • Narcotic Antagonists
  • Neurotransmitter Agents
  • Pyrrolidines
  • Receptors, Adrenergic, alpha-2
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu
  • Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
  • ICI 204448
  • Yohimbine
  • Naloxone
  • norbinaltorphimine
  • Naltrexone
  • Norepinephrine