Opposing actions of CRF-R1 and CB1 receptors on VTA-GABAergic plasticity following chronic exposure to ethanol

Neuropsychopharmacology. 2018 Sep;43(10):2064-2074. doi: 10.1038/s41386-018-0106-9. Epub 2018 Jun 9.

Abstract

Dopamine neurons in the ventral tegmental area (VTA) influence learned behaviors and neuropsychiatric diseases including addiction. The stress peptide corticotrophin-releasing factor (CRF) contributes to relapse to drug and alcohol seeking following withdrawal, although the cellular actions are poorly understood. In this study, we show that presynaptic CRF type 1 receptors (CRF-R1) potentiate GABA release onto mouse VTA dopamine neurons via a PKC-Ca2+ signaling mechanism. In naive animals, activation of CRF-R1 by bath application of CRF or ethanol enhanced GABAA inhibitory postsynaptic currents (IPSCs). Following 3 days of withdrawal from four weekly cycles of chronic intermittent ethanol (CIE) vapor exposure, spontaneous IPSC frequency was enhanced while CRF and ethanol potentiation of IPSCs was intact. However, withdrawal for 3 weeks or more was associated with reduced spontaneous IPSC frequency and diminished CRF and ethanol responses. Long-term withdrawal was also accompanied by decreased sensitivity to the CB1 receptor agonist WIN55212 as well as greatly enhanced sensitivity to the CB1 antagonist AM251. Inclusion of BAPTA in the internal recording solution restored the responsiveness to CRF or ethanol and reduced the potentiating actions of AM251. Together, these data suggest that GABAA inhibition of VTA dopamine neurons is regulated by presynaptic actions of CRF and endocannabinoids and that long-term withdrawal from CIE treatment enhances endocannabinoid-mediated inhibition, thereby suppressing CRF facilitation of GABA release. Such findings have implications for understanding the impact of chronic alcohol on stress-related, dopamine-mediated alcohol-seeking behaviors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcoholism / psychology
  • Animals
  • Benzoxazines / pharmacology
  • Central Nervous System Depressants / pharmacology*
  • Corticotropin-Releasing Hormone / pharmacology
  • Dopaminergic Neurons / drug effects
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Ethanol / pharmacology*
  • Excitatory Postsynaptic Potentials / drug effects
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Morpholines / pharmacology
  • Naphthalenes / pharmacology
  • Neuronal Plasticity / drug effects*
  • Piperidines / pharmacology
  • Pyrazoles / pharmacology
  • Receptor, Cannabinoid, CB1 / agonists
  • Receptor, Cannabinoid, CB1 / drug effects*
  • Receptors, Corticotropin-Releasing Hormone / agonists
  • Receptors, Corticotropin-Releasing Hormone / drug effects*
  • Receptors, Presynaptic / drug effects
  • Substance Withdrawal Syndrome / psychology
  • Ventral Tegmental Area / drug effects*
  • gamma-Aminobutyric Acid / physiology*

Substances

  • Benzoxazines
  • Central Nervous System Depressants
  • Morpholines
  • Naphthalenes
  • Piperidines
  • Pyrazoles
  • Receptor, Cannabinoid, CB1
  • Receptors, Corticotropin-Releasing Hormone
  • Receptors, Presynaptic
  • AM 251
  • Ethanol
  • Egtazic Acid
  • gamma-Aminobutyric Acid
  • CRF receptor type 1
  • (3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone
  • Corticotropin-Releasing Hormone
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid