Effect of morphine on electrophysiological properties of circular and longitudinal muscles

R. J. Gilbert, S. K. Sarna, D. R. Harder

Research output: Contribution to journalArticle

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Abstract

We have measured the effects of morphine on the intracellular electrophysiological properties of smooth muscle cells from the circular and longitudinal muscle layers of the canine jejunum. Morphine hyperpolarized the circular muscle membrane by ~12 mV and increased the electrical control activity (ECA) amplitude and dV/dt. Morphine had no significant effect on the electrical properties of the longitudinal muscle cells. The morphine-induced hyperpolarization of the circular muscle membrane was blocked by tetrodotoxin (TTX) and naloxone, but not by atropine and hexamethonium, propranolol, or phentolamine. Morphine significantly increased the slope of the resting membrane potential vs. the log of the potassium concentration in bathing medium from 38 to 50 mV/decade. The sodium permeability to potassium permeability ratio, calculated from the Goldman constant field equation, was reduced by morphine from 0.13 to 0.07 at 4 mM of K+. The above results suggest that when measured by intracellular techniques, morphine hyperpolarizes the circular muscle membrane by release of a nonadrenergic, noncholinergic neurotransmitter. The mechanism of this hyperpolarization is consistent with an increase in potassium conductance.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume252
Issue number3
StatePublished - 1987
Externally publishedYes

Fingerprint

Morphine
Muscles
Potassium
Membranes
Permeability
Hexamethonium
Phentolamine
Tetrodotoxin
Jejunum
Naloxone
Atropine
Propranolol
Membrane Potentials
Muscle Cells
Smooth Muscle Myocytes
Neurotransmitter Agents
Canidae
Sodium

ASJC Scopus subject areas

  • Physiology
  • Gastroenterology

Cite this

Effect of morphine on electrophysiological properties of circular and longitudinal muscles. / Gilbert, R. J.; Sarna, S. K.; Harder, D. R.

In: American Journal of Physiology - Gastrointestinal and Liver Physiology, Vol. 252, No. 3, 1987.

Research output: Contribution to journalArticle

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