Background-Corticotropin-releasing factor (CRF) and gamma-aminobutyric acid (GABA)ergic systems in the central amygdala (CeA) are implicated in the high-anxiety, high-drinking profile associated with ethanol dependence. Ethanol augments CeA GABA release in ethanol-naive rats and mice.

Dieting to control body weight involves cycles of deprivation from palatable food that can promote compulsive eating. The present study shows that rats withdrawn from intermittent access to palatable food exhibit overeating of palatable food upon renewed access and an affective withdrawal-like state characterized by corticotropin-releasing factor-1 (CRF 1) receptor antagonistreversible behaviors, including hypophagia, motivational deficits to obtain less palatable food, and anxiogenic-like behavior. Withdrawal was accompanied by increased CRF expression and CRF 1 electrophysiological responsiveness in the central nucleus of the amygdala. We propose that recruitment of anti-reward extrahypothalamic CRF-CRF 1 systems during withdrawal from palatable food, analogous to abstinence from abused drugs, may promote compulsive selection of palatable food, undereating of healthier alternatives, and a negative emotional state when intake of palatable food is prevented.eating disorders ͉ obesity ͉ palatability ͉ palatable food dependence ͉ withdrawal F orms of obesity and eating disorders, similar to drug addiction, can be conceptualized as chronic relapsing conditions with alternating periods of abstinence (i.e., dieting to avoid ''forbidden'' palatable foods) and relapse (i.e., compulsive, often uncontrollable, eating of high-palatable foods) that continue despite negative consequences (1). Although the positive reinforcing properties of palatable foods are well known (2, 3), less attention has been given to their negative reinforcing properties (4-6), namely the increased probability of a behavioral response produced by removal of an aversive stimulus (e.g., intake of palatable food to relieve negative emotional states). Intermittent cycles of extended use of drugs of abuse can progressively lead to ''affective dependence,'' observed as a need for higher and/or more regular quantities of the drug to maintain a given emotional set point as well as a negative emotional state upon cessation of drug intake (7,8). Such affective withdrawal may maintain use and motivate relapse via the negative reinforcing properties of continuing and resuming drug use, respectively (7,8).Extrahypothalamic corticotropin-releasing factor (CRF) brain stress systems are putatively involved in the transition from drug use to dependence, during which intake of abused drugs becomes increasingly motivated by these negative, rather than positive, reinforcement mechanisms. CRF plays a motivationally relevant role in withdrawal syndromes for every major drug of abuse, including alcohol, nicotine, cocaine, opiates, amphetamines, and tetrahydrocannabinol (7,8). By analogy, repeated cycles of intermittent, extended access to highly palatable food were hypothesized to induce CRF system neuroadaptations similar to those seen in drug dependence models (4, 5, 9). ResultsIntermittent, extended access to palatable food progressively leads to undereating of less preferred diets when palatable food is not available and to overeating of palatable food upon renewed ...

In the central amygdala (CeA), ethanol acts via corticotrophinreleasing factor (CRF) type 1 receptors to enhance GABA release. Amygdala CRF mediates anxiety associated with stress and drug dependence, and it regulates ethanol intake. Because mutant mice that lack PKC exhibit reduced anxiety-like behavior and alcohol consumption, we investigated whether PKC lies downstream of CRF1 receptors in the CeA. Compared with PKC ؉/؉ CeA neurons, PKC ؊/؊ neurons showed increased GABAergic tone due to enhanced GABA release. CRF and ethanol stimulated GABA release in the PKC ؉/؉ CeA, but not in the PKC ؊/؊ CeA. A PKC-specific inhibitor blocked both CRF-and ethanol-induced GABA release in the PKC ؉/؉ CeA, confirming findings in the PKC ؊/؊ CeA. These results identify a PKC signaling pathway in the CeA that is activated by CRF 1 receptor stimulation, mediates GABA release at nerve terminals, and regulates anxiety and alcohol consumption.GABA transmission ͉ alcohol ͉ electrophysiology ͉ anxiety ͉ presynaptic transmission

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.

The central amygdala (CeA) plays a major role in alcohol dependence and reinforcement, and behavioral and neurochemical evidence suggest a role for the endocannabinoid (eCB) system in ethanol binging and dependence. We used the slice preparation to investigate the physiological role of cannabinoids and their interaction with ethanol on inhibitory synaptic transmission in CeA. Superfusion of the cannabinoid receptor (CB1) agonist WIN55212-2 (WIN2) onto CeA neurons decreased evoked GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) in a concentration-dependent manner, an effect prevented by the CB1 antagonists Rimonabant (SR141716, SR1) and AM251. SR1 or AM251 applied alone augmented IPSPs, revealing a tonic eCB activity that decreased inhibitory transmission in CeA. Paired-pulse analysis suggested a presynaptic CB1 mechanism. Intracellular BAPTA abolished the ability of AM251 to augment IPSPs, demonstrating the eCB-driven nature and postsynaptic origin of the tonic CB1-dependent control of GABA release. Superfusion of ethanol increased IPSPs and addition of WIN2 reversed the ethanol effect. Similarly, prior superfusion of WIN2 prevented subsequent ethanol effects on GABAergic transmission. The ethanol-induced augmentation of IPSPs was additive to CB1 blockade, ruling out a participation of CB1 in the action of acute ethanol. Our study points to an important role of CB1 in CeA where the eCBs tonically regulate neuronal activity, and suggests a potent mechanism for modulating CeA tone during challenge with ethanol.

Toll-like receptor 4 (TLR4) is a critical component of innate immune signaling and has been implicated in alcohol responses in preclinicaland clinical models. Members of the Integrative Neuroscience Initiative on Alcoholism (INIA-Neuroimmune) consortium tested the hypothesis that TLR4 mediates excessive ethanol drinking using the following models: (1) Tlr4 knock-out (KO) rats, (2) selective knockdown of Tlr4 mRNA in mouse nucleus accumbens (NAc), and (3) injection of the TLR4 antagonist (ϩ)-naloxone in mice. Lipopolysaccharide (LPS) decreased food/water intake and body weight in ethanol-naive and ethanol-trained wild-type (WT), but not Tlr4 KO rats. There were no consistent genotypic differences in two-bottle choice chronic ethanol intake or operant self-administration in rats before or after dependence. In mice, (ϩ)-naloxone did not decrease drinking-in-the-dark and only modestly inhibited dependence-driven consumption at the highest dose. Tlr4 knockdown in mouse NAc did not decrease drinking in the two-bottle choice continuous or intermittent access tests. However, the latency to ethanol-induced loss of righting reflex increased and the duration decreased in KO versus WT rats. In rat central amygdala neurons, deletion of Tlr4 altered GABA A receptor function, but not GABA release. Although there were no genotype differences in acute ethanol effects before or after chronic intermittent ethanol exposure, genotype differences were observed after LPS exposure. Using different species and sexes, different methods to inhibit TLR4 signaling, and different ethanol consumption tests, our comprehensive studies indicate that TLR4 may play a role in ethanol-induced sedation and GABA A receptor function, but does not regulate excessive drinking directly and would not be an effective therapeutic target.

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This article summarizes the proceedings of a symposium that was presented at a conference entitled "Alcoholism and Stress: A Framework for Future Treatment Strategies". The conference was held in Volterra, Italy on May 6-9, 2008 and this symposium was chaired by Jeff L. Weiner. The overall goal of this session was to review recent findings that may shed new light on the neurobiological mechanisms that underlie the complex relationships between stress, anxiety, and alcoholism. Dr. Danny Winder described a novel interaction between D1 receptor activation and the CRF system Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptAlcohol. Author manuscript; available in PMC 2010 November 1. Published in final edited form as:Alcohol.