Chronic Ethanol Exposure and Protracted Abstinence Alter NMDA Receptors in Central Amygdala

Abstract

We recently reported that chronic ethanol treatment (CET) and early withdrawal (2-8 h) altered glutamatergic transmission at both preand postsynaptic sites in central nucleus of the amygdala (CeA). Acute ethanol (44 mM) inhibited the NMDA receptor (NMDAR)-mediated EPSCs (NMDA-EPSCs) more in CeA neurons from CET rats than from naïve rats and also decreased paired-pulse facilitation (PPF) of NMDA-EPSCs only in CET rats. To determine whether these CET effects persisted after prolonged withdrawal, we recorded intracellularly in rat CeA slices and measured mRNA and protein expression of CeA NMDAR subunits from CET rats and those withdrawn from ethanol for 1 or 2 weeks. At 1 week withdrawal, acute ethanol decreased evoked NMDA-EPSC amplitudes and NMDA currents induced by exogenous NMDA (B20%) equally to that in naïve rats, indicating that CET effects on postsynaptic mechanisms reversed 1 week after CET cessation. However, acute ethanol still decreased PPF of NMDA-EPSCs, indicating that the acute ethanolinduced increase in glutamate release in CeA seen in CET rats was still present at this time. CET also significantly increased mRNA levels of NR1 and NR2B NMDAR subunits compared to control rats. At 1 week withdrawal, mRNA levels for NR1 and NR2B subunits were significantly decreased. These changes reversed at 2 weeks withdrawal. In Western blots, a significant increase in protein for all three subunits occurred in CeA from CET rats, but not after 1 and 2 weeks of withdrawal. These data indicate that CET induces reversible neuroadaptations in synaptic function, gene expression, and protein composition of NMDAR at CeA synapses. Neuropsychopharmacology (2006) 31, 988-996.

NMDA Receptors Regulate Nicotine-Enhanced Brain Reward Function and Intravenous Nicotine Self-Administration: Role of the Ventral Tegmental Area and Central Nucleus of the Amygdala

“…We found that the expression of NMDA receptor subunits (NR2A, NR2B, and/or NR1) was increased in the VTA and CeA, decreased in the PFC, and unaltered in the NAcc, BLA, or CPu, of nicotine self-administering rats compared with controls. Importantly, similar increases in NMDA receptor subunit expression in the VTA and CeA and decreases in the PFC have been observed in rats self-administering cocaine, opiates, or alcohol and in post-mortem brain tissues from human cocaine users (Ortiz et al, 1995;Ghasemzadeh et al, 1999;Lu et al, 2003Lu et al, , 2005Tang et al, 2003;Turchan et al, 2003;Roberto et al, 2006;Ben-Shahar et al, 2007). The effects of self-administered nicotine on NMDA receptor subunit expression were far more pronounced in the CeA compared with the VTA.…”

“…Amygdala slices (400 mm) were prepared as described previously (Roberto et al, 2006), superfused continuously (flow rate of 2-4 ml/min) with warm (311C), gassed artificial cerebrospinal fluid (aCSF) of the following composition (in mM): NaCl, 130; KCl, 3.5; NaH 2 PO 4 , 1.25; MgSO 4 7H 2 O, 1.5; CaCl 2 , 2.0; NaHCO 3 , 24; glucose, 10; and gassed with 95% O 2 and 5% CO 2 . CeA neurons were recorded with sharp micropipettes (3 M KCl) using discontinuous voltage-or current-clamp mode.…”

Cognitive and emotional consequences of binge drinking: role of amygdala and prefrontal cortex

“…An increased probability of glutamate release from the presynaptic terminal (Lack et al 2007), and increased postsynaptic NMDA receptor function (Roberto et al 2006;Lack et al 2007) may lead to increased postsynaptic AMPA receptor function (Lack et al 2007). We suggest that this imbalance towards glutamatergic excitatory transmission might have consequences similar to overactivation of glutamatergic synapses that occur during LTP.…”

“…Several pieces of evidence indicate that intermittent exposure to ethanol and withdrawal facilitates glutamatergic synaptic transmission in both central (Roberto et al 2006) and basolateral amygdala ( Floyd et al 2003;Lack et al 2007). An increased probability of glutamate release from the presynaptic terminal (Lack et al 2007), and increased postsynaptic NMDA receptor function (Roberto et al 2006;Lack et al 2007) may lead to increased postsynaptic AMPA receptor function (Lack et al 2007).…”

A Molecular Mechanism of Ethanol Dependence: The Influence of the Ionotropic Glutamate Receptor Activated by N-Methyl-D-Aspartate

“…Several studies have reported increases in the expression level of several subunits of the NMDAR such as NR1, NR2A, and NR2B during the adaptive phase under chronic alcohol exposure conditions (Snell et al, 1996;Roberto et al, 2004;Roberto et al, 2006;Lack et al, 2007). Other studies have reported increases in the accumulation of synaptic NMDARs during this phase as well (Carpenter-Hyland et al, 2004;Clapp et al, 2010).…”