title: Inhibitor of cyclic AMP-dependent protein kinase blocks opioid-induced prolongation of the action potential of mouse sensory ganglion neurons in dissociated cell cultures.
abstract: The duration of the calcium component of the action potential (APD) of dorsal root ganglion (DRG) neurons in mouse spinal cord-ganglion explants has been shown to be dually modulated via excitatory and inhibitory opioid receptors. In order to determine if opioid-induced APD prolongation is modulated by receptors that are positively coupled to the adenylate cyclase (AC)/cyclic AMP second messenger system, whole-cell recordings were made from mouse DRG neurons grown in dissociated cell cultures. Tests for opioid responsivity were carried out after intracellular dialysis of an inhibitor of cAMP-dependent protein kinase (PKI). In control recordings, both DADLE-induced APD prolongation as well as shortening were prevented by co-perfusion with the opioid antagonist, diprenorphine (10 nM). Intracellular dialysis of PKI in these neurons completely blocked opioid-induced APD prolongation but did not attenuate APD shortening generally elicited by higher opioid concentrations. Bath perfusion of 10 nM DADLE elicited APD prolongation in 59% of the DRG neurons (n = 34) tested with control solution in the recording pipette, whereas none showed APD prolongation when the pipette contained PKI (n = 18). In control tests with 1 microM DADLE, the APD was prolonged in 37% of the cells and shortened in 26% (n = 19); in contrast, a matched group of PKI-treated cells showed no APD prolongation, whereas 42% showed APD shortening (n = 26). The results support the hypothesis that opioid-induced APD prolongation in DRG neurons is mediated by opioid receptor subtypes that are positively coupled via Gs to AC/cAMP-dependent voltage-sensitive ionic conductances.
authors.affiliation: Department of Neuroscience, Rose F. Kennedy Center for Research in Mental Retardation and Human Development, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY 10461.
authors.forename: G G
authors.initials: GG
authors.lastname: Chen
authors.forename: A
authors.initials: A
authors.lastname: Chalazonitis
authors.forename: K F
authors.initials: KF
authors.lastname: Shen
authors.forename: S M
authors.initials: SM
authors.lastname: Crain
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002352:Carrier Proteins / Q000494:pharmacology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism / Q000502:physiology*; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine; D005727:Ganglia, Spinal / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D009475:Neurons, Afferent / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C015482:protein kinase modulator; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D000242:Cyclic AMP; D011494:Protein Kinases