Opioids at low concentration decrease openings of K+ channels in sensory ganglion neurons

doi:10.1016/0006-8993(91)90737-G

Brain Research

Volume 558, Issue 1, 30 August 1991, Pages 166-170

https://doi.org/10.1016/0006-8993(91)90737-G Get rights and content

Abstract

Previous studies showed that low concentrations of opioids prolong the calcium-dependent component of the action potential duration (APD) of dorsal root ganglion (DRG) neurons, whereas higher concentrations shorten the APD. In the present study whole-cell voltage-clamp, as well as cell-attached membrane-patch voltage-clamp, recordings demonstrate that application of picomolar to nanomolar concentrations of μ, δ or κ opioid agonists (DAGO, DPDPE or dynorphin) to DRG neurons in dissociated cell cultures reversibly decreased the activities of voltage-sensitive K⁺ channels. Pretreatment of DRG neurons with the opioid receptor antagonists, naloxone (30 nM) or diprenorphine (1 nM) prevented μ/δ or κ opioid-induced decreases in K⁺ channel activities, respectively. Since opioids added to the bath solution decreased the activities of K⁺ channels in the membrane patch sealed off by the pipette tip, our results provide strong evidence that some modes of excitatory modulation of the action potential of DRG neurons are mediated by diffusible second messengers. The data are consonant with our previous studies indicating that opioids can elicit excitatory effects on sensory neurons via cholera toxin-sensitive G_s-linked excitatory opioid receptors coupled to cyclic AMP-dependent ionic channels.

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: This work was supported by Research Grants DA-05203 and DA-02031 to S.M.C. The DRG cell cultures were prepared by Peter Vanamee in tissue culture facilities kindly provided by Dr. Murray B. Bornstein. Analyses of the single-channel activities of the DRG neurons were carried out by S.F.F., using computer facilities kindly provided by Dr. Peter R. Brink, Department of Physiology and Biophysics, State University of New York at Stony Brook, NY, U.S.A.

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Opioids at low concentration decrease openings of K+ channels in sensory ganglion neurons

Abstract

Biophys. J.

Neuroscience

Brain Research

Trends Pharmacol. Sci.

Trends Physiol. Sci.

Biophys. J.

Brain Research

Neuropharmacology

Brain Research

Opioids at low concentration decrease openings of K⁺ channels in sensory ganglion neurons