Ethanol produces corticotropin-releasing factor receptor-dependent enhancement of spontaneous glutamatergic transmission in the mouse central amygdala.
BACKGROUND
Ethanol (EtOH) modulation of central amygdala (CeA) neurocircuitry plays a key role in the development of alcoholism via activation of the corticotropin-releasing factor (CRF) receptor (CRFR) system. Previous work has predominantly focused on EtOH × CRF interactions on the CeA GABA circuitry; however, our laboratory recently showed that CRF enhances CeA glutamatergic transmission. Therefore, this study sought to determine whether EtOH modulates CeA glutamate transmission via activation of CRF signaling.


METHODS
The effects of EtOH on spontaneous excitatory postsynaptic currents (sEPSCs) and basal resting membrane potentials were examined via standard electrophysiology methods in adult male C57BL/6J mice. Local ablation of CeA CRF neurons (CRF(CeAhDTR) ) was achieved by targeting the human diphtheria toxin receptor (hDTR) to CeA CRF neurons with an adeno-associated virus. Ablation was quantified post hoc with confocal microscopy. Genetic targeting of the diphtheria toxin active subunit to CRF neurons (CRF(DTA) mice) ablated CRF neurons throughout the central nervous system, as assessed by quantitative reverse transcriptase polymerase chain reaction quantification of CRF mRNA.


RESULTS
Acute bath application of EtOH significantly increased sEPSC frequency in a concentration-dependent manner in CeA neurons, and this effect was blocked by pretreatment of co-applied CRFR1 and CRFR2 antagonists. In experiments utilizing a CRF-tomato reporter mouse, EtOH did not significantly alter the basal membrane potential of CeA CRF neurons. The ability of EtOH to enhance CeA sEPSC frequency was not altered in CRF(CeAhDTR) mice despite a ~78% reduction in CeA CRF cell counts. The ability of EtOH to enhance CeA sEPSC frequency was also not altered in the CRF(DTA) mice despite a 3-fold reduction in CRF mRNA levels.


CONCLUSIONS
These findings demonstrate that EtOH enhances spontaneous glutamatergic transmission in the CeA via a CRFR-dependent mechanism. Surprisingly, our data suggest that this action may not require endogenous CRF.
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee.
Yuval
Y
Silberman
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee.|Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, Tennessee.
Tracy L
TL
Fetterly
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee.
Elias K
EK
Awad
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee.
Elana J
EJ
Milano
Section on Fundamental Neuroscience, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland.
Ted B
TB
Usdin
Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee.|Vanderbilt Brain Institute, Vanderbilt University School of Medicine, Nashville, Tennessee.
Danny G
DG
Winder
D000818:Animals; D066274:Central Amygdaloid Nucleus / Q000187:drug effects* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009924:Organ Culture Techniques; D018019:Receptors, Corticotropin-Releasing Hormone / Q000819:agonists / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects* / Q000502:physiology
D018019:Receptors, Corticotropin-Releasing Hormone; D000431:Ethanol; D018698:Glutamic Acid
CRF Reporter Mice; Central Nucleus of the Amygdala; Diphtheria Toxin; Selective Deletion; Whole-Cell Patch-Clamp Electrophysiology