Our major objective are: 1) to analyze mechanisms underlying the dual receptor-mediated excitatory and inhibitory modulation of the action potentials (APs) of mouse dorsal-root ganglion (DRG) neurons that we have observed in explants and dissociated cell cultures; 2) to test the hypothesis that enhancement of the adenylate cyclase (AC)/cyclic AMP system is causally related to the tolerance that occurs in DRG neuron APs and dorsal-horn network response after chronic opioid treatment of DRG-cord cultures. Whereas the duration of the AP calcium component (APD) of naive DRG neurons is generally shortened by acute exposure to high (muM) concentrations of opioids, low (nM) levels of specific mu, delta and kappa opioids elicit APD prolongation in many of the same cells. Both excitatory and inhibitory opioid effects are prevented by naloxone or diprenorphine. Intracellular and whole- cell patch-clamp recording will be used to analyze this dual opioid modulation of DRG neurons in explant and dissociated-cell cultures. Excitatory vs. inhibitory opioid receptors will be characterized by electrophysiologic tests during systematic treatments with specific opioid agonists, antagonists and receptor inactivators. These physiologic studies will be coordinated with opioid binding assays and receptor autoradiography after similar treatments, including pertussis (PTX) vs. cholera toxin (CTX). To further evaluate our evidence that opioid-induced APD prolongation is mediated by receptors positively coupled via Gs to the AC/cAMP/protein kinase A(PKA) system, the opioid responsivity of DRG neurons will be tested extracellular or intracellular perfusion with CTX vs. PTX, cAMP, PKA, inhibitors of AC and PKA, specific ion channel blockers, or altered ion concentrations. Linkages of excitatory opioid receptors with specific K+ and Ca2+ conductances in DRG cells will be analyzed. Correlative biochemical assays of AC activity of these neuros will made, especially during the physiologic expression of tolerance and during the increase in opioid excitatory responsiveness in DRG cells chronically exposed to specific mu, delta, or kappa opioids. Correlative binding assays and autoradiography will be made to determine if specific subtypes of opioid receptors are up-regulated or down-regulated in tolerant DRG neurons. These studies will provide valuable insights into cellular compensatory mechanisms that mediate tolerance to opioid analgesic effects in primary afferent synaptic networks and clues to some of the addictive and euphoric effects of opioids in the CNS.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
2R01DA002031-10
Application #
3207081
Study Section
Pharmacology I Research Subcommittee (DABR)
Project Start
1978-07-01
Project End
1992-02-29
Budget Start
1989-03-01
Budget End
1990-02-28
Support Year
10
Fiscal Year
1989
Total Cost
Indirect Cost
Name
Albert Einstein College of Medicine
Department
Type
Schools of Medicine
DUNS #
009095365
City
Bronx
State
NY
Country
United States
Zip Code
10461
Shen, K F; Crain, S M (1994) Nerve growth factor rapidly prolongs the action potential of mature sensory ganglion neurons in culture, and this effect requires activation of Gs-coupled excitatory kappa-opioid receptors on these cells. J Neurosci 14:5570-9
Shen, K F; Crain, S M (1994) Antagonists at excitatory opioid receptors on sensory neurons in culture increase potency and specificity of opiate analgesics and attenuate development of tolerance/dependence. Brain Res 636:286-97
Cruciani, R A; Dvorkin, B; Klinger, H P et al. (1994) Presence in neuroblastoma cells of a mu 3 receptor with selectivity for opiate alkaloids but without affinity for opioid peptides. Brain Res 667:229-37
Cruciani, R A; Dvorkin, B; Morris, S A et al. (1993) Direct coupling of opioid receptors to both stimulatory and inhibitory guanine nucleotide-binding proteins in F-11 neuroblastoma-sensory neuron hybrid cells. Proc Natl Acad Sci U S A 90:3019-23
Fan, S F; Shen, K F; Crain, S M (1993) mu and delta opioid agonists at low concentrations decrease voltage-dependent K+ currents in F11 neuroblastoma x DRG neuron hybrid cells via cholera toxin-sensitive receptors. Brain Res 605:214-20
Crain, S M; Shen, K F (1992) After GM1 ganglioside treatment of sensory neurons naloxone paradoxically prolongs the action potential but still antagonizes opioid inhibition. J Pharmacol Exp Ther 260:182-6
Shen, K F; Crain, S M (1992) Chronic selective activation of excitatory opioid receptor functions in sensory neurons results in opioid 'dependence' without tolerance. Brain Res 597:74-83
Crain, S M; Shen, K F (1992) After chronic opioid exposure sensory neurons become supersensitive to the excitatory effects of opioid agonists and antagonists as occurs after acute elevation of GM1 ganglioside. Brain Res 575:13-24
Fan, S F; Shen, K F; Scheideler, M A et al. (1992) F11 neuroblastoma x DRG neuron hybrid cells express inhibitory mu- and delta-opioid receptors which increase voltage-dependent K+ currents upon activation. Brain Res 590:329-33
Terwilliger, R Z; Beitner-Johnson, D; Sevarino, K A et al. (1991) A general role for adaptations in G-proteins and the cyclic AMP system in mediating the chronic actions of morphine and cocaine on neuronal function. Brain Res 548:100-10

Showing the most recent 10 out of 28 publications