Aberrant synaptic activation of N-methyl-D-aspartate receptors underlies ethanol withdrawal hyperexcitability.
Chronic ethanol exposure may induce neuroadaptive responses in N-methyl-d-aspartate (NMDA) receptors, which are thought to underlie a variety of alcohol-related brain disorders. Here, we demonstrate that hyperexcitability triggered by withdrawal from chronic ethanol exposure is associated with increases in both synaptic NMDA receptor expression and activation. Withdrawal from chronic ethanol exposure (75 mM ethanol, 5-9 days) elicited robust and prolonged epileptiform activity in CA1 pyramidal neurons from hippocampal explants, which was absolutely dependent upon NMDA receptor activation but independent of chronic inhibition of protein kinase A (PKA). Analysis of Sr(2+)-supported asynchronous NMDA receptor-mediated miniature excitatory postsynaptic currents (mEPSCs) was employed to assess changes in NMDA neurotransmission. After chronic exposure, ethanol withdrawal was associated with an increase in mEPSC amplitude 3.38-fold over that after withdrawal from acute ethanol exposure. Analysis of paired evoked alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid EPSCs and spontaneous mEPSCs indicated that withdrawal after chronic exposure was also associated with a selective increase in action potential evoked but not spontaneous transmitter release probability. Immunoblot analysis revealed significant increases in total NR1, NR2A, and NR2B subunit expression after chronic exposure and unaffected by PKA-inhibition manner. Confocal imaging studies indicate that increased NR1 subunit expression was associated with increased density of NR1 expression on dendrites in parallel with a selective increase in the size of NR1 puncta on dendritic spines. Therefore, neuroadaptation to chronic ethanol exposure in NMDA synaptic transmission is responsible for aberrant network excitability after withdrawal and results from changes in both postsynaptic function as well as presynaptic release.
Hendricson
Adam W
AW
Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712-0125, USA.
Maldve
Regina E
RE
Salinas
Armando G
AG
Theile
Jonathan W
JW
Zhang
Tao A
TA
Diaz
Laurea M
LM
Morrisett
Richard A
RA
D000818:Animals; D015153:Blotting, Western; D002492:Central Nervous System Depressants / Q000009:adverse effects*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004563:Electrochemistry; D004594:Electrophysiology; D000431:Ethanol / Q000009:adverse effects*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials; D005260:Female; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D006624:Hippocampus / Q000502:physiology; D006948:Hyperkinesis / Q000503:physiopathology*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008297:Male; D018613:Microscopy, Confocal; D009045:Motor Endplate / Q000502:physiology; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012640:Seizures / Q000503:physiopathology; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D002492:Central Nervous System Depressants; D018690:Excitatory Amino Acid Agonists; C409466:NR1 NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D049452:Green Fluorescent Proteins; D000431:Ethanol; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D017868:Cyclic AMP-Dependent Protein Kinases