Further evidence of an inverse genetic relationship between innate differences in alcohol preference and alcohol withdrawal magnitude in multiple selectively bred rat lines

RNA-Seq Analysis of Genetic and Transcriptome Network Effects of Dual-Trait Selection for Ethanol Preference and Withdrawal Using SOT and NOT Genetic Models

BACKGROUND

Genetic factors significantly affect alcohol consumption and vulnerability to withdrawal. Furthermore, some genetic models showing predisposition to severe withdrawal are also predisposed to low ethanol (EtOH) consumption and vice versa, even when tested independently in naïve animals.

METHODS

Beginning with a C57BL/6J × DBA/2J F2 intercross founder population, animals were simultaneously selectively bred for both high alcohol consumption and low acute withdrawal (SOT line), or vice versa (NOT line). Using randomly chosen fourth selected generation (S4) mice (N = 18-22/sex/line), RNA-Seq was employed to assess genome-wide gene expression in ventral striatum. The MegaMUGA array was used to detect genome-wide genotypic differences. Differential gene expression and the weighted gene co-expression network analysis were implemented as described elsewhere (Genes Brain Behav 16, 2017, 462).

RESULTS

The new selection of the SOT and NOT lines was similar to that reported previously (Alcohol Clin Exp Res 38, 2014, 2915). One thousand eight hundred and sixteen transcripts were detected as differentially expressed between the lines. For genes more highly expressed in the SOT line, there was enrichment in genes associated with cell adhesion, synapse organization, and postsynaptic membrane. The genes with a cell adhesion annotation included 23 protocadherins, Mpdz and Dlg2. Genes with a postsynaptic membrane annotation included Gabrb3, Gphn, Grid1, Grin2b, Grin2c, and Grm3. The genes more highly expressed in the NOT line were enriched in a network module (red) with annotations associated with mitochondrial function. Several of these genes were module hub nodes, and these included Nedd8, Guk1, Elof1, Ndufa8, and Atp6v1f.

CONCLUSIONS

Marked effects of selection on gene expression were detected. The NOT line was characterized by higher expression of hub nodes associated with mitochondrial function. Genes more highly expressed in the SOT aligned with previous findings, for example, Colville and colleagues (Genes Brain Behav 16, 2017, 462) that both high EtOH preference and consumption are associated with effects on cell adhesion and glutamate synaptic plasticity.

Alcoholic Hepatitis: Lost in Translation

Alcoholic hepatitis is the most severe and acute form of alcoholic liver disease. The mortality rate associated with alcoholic hepatitis is high, largely due to the lack of suitable pharmacological interventions. While there has been substantial research in the area, generating pharmacological interventions has been plagued by the lack of a robust mouse model both for testing and for understanding the underlying pathology. A number of major notable advances have been made in this area recently, with the goal of generating a mouse model of alcoholic hepatitis. The purpose of this article is to review recent advances in modeling alcoholic liver disease both in vitro and in vivo in the mouse, and place them in the context of the greater spectrum of alcoholic liver disease, with a focus on how we can translate current advances into a high-fidelity model of alcoholic hepatitis. In addition, we will review the basic mechanisms of alcoholic hepatitis as it is currently understood, focusing on recent advancements in diagnosis, prognosis and current pathophysiology, especially as it relates to the profound immune dysfunction present during alcoholic hepatitis.

Genetic correlation between alcohol preference and conditioned fear: Exploring a functional relationship

Post-traumatic stress disorder (PTSD) and alcohol-use disorders have a high rate of co-occurrence, possibly because they are regulated by common genes. In support of this idea, mice selectively bred for high (HAP) alcohol preference show greater fear potentiated startle (FPS), a model for fear-related disorders such as PTSD, compared to mice selectively bred for low (LAP) alcohol preference. This positive genetic correlation between alcohol preference and FPS behavior suggests that the two traits may be functionally related. This study examined the effects of fear conditioning on alcohol consumption and the effects of alcohol consumption on the expression of FPS in male and female HAP2 and LAP2 mice. In experiment 1, alcohol consumption (g/kg) under continuous-access conditions was monitored daily for 4 weeks following a single fear-conditioning or control treatment (foot shock and no shock). FPS was assessed three times (once at the end of the 4-week alcohol access period, once at 24 h after removal of alcohol, and once at 6-8 days after removal of alcohol), followed by two more weeks of alcohol access. Results showed no change in alcohol consumption, but alcohol-consuming, fear-conditioned, HAP2 males showed increased FPS at 24 h during the alcohol abstinence period compared to control groups. In experiment 2, alcohol consumption under limited-access conditions was monitored daily for 4 weeks. Fear-conditioning or control treatments occurred four times during the first 12 days and FPS testing occurred four times during the second 12 days of the 4-week alcohol consumption period. Results showed that fear conditioning increased alcohol intake in both HAP2 and LAP2 mice immediately following the first conditioning session. Fear-conditioned HAP2 but not LAP2 mice showed greater alcohol intake compared to control groups on drinking days that occurred between fear conditioning and FPS test sessions. FPS did not change as a function of alcohol consumption in either line. These results in mice help shed light on how a genetic propensity toward high alcohol consumption may be related to the risk for developing PTSD and co-morbid alcohol-use disorders in humans.

Sex Differences in Behavioral Dyscontrol: Role in Drug Addiction and Novel Treatments

The purpose of this review is to discuss recent findings related to sex differences in behavioral dyscontrol that lead to drug addiction, and clinical implications for humans are discussed. This review includes research conducted in animals and humans that reveals fundamental aspects of behavioral dyscontrol. The importance of sex differences in aspects of behavioral dyscontrol, such as impulsivity and compulsivity, is discussed as major determinants of drug addiction. Behavioral dyscontrol during adolescence is also an important consideration, as this is the time of onset for drug addiction. These vulnerability factors additively increase drug-abuse vulnerability, and they are integral aspects of addiction that covary and interact with sex differences. Sex differences in treatments for drug addiction are also reviewed in terms of their ability to modify the behavioral dyscontrol that underlies addictive behavior. Customized treatments to reduce behavioral dyscontrol are discussed, such as (1) using natural consequences such as non-drug rewards (e.g., exercise) to maintain abstinence, or using punishment as a consequence for drug use, (2) targeting factors that underlie behavioral dyscontrol, such as impulsivity or anxiety, by repurposing medications to relieve these underlying conditions, and (3) combining two or more novel behavioral or pharmacological treatments to produce additive reductions in drug seeking. Recent published work has indicated that factors contributing to behavioral dyscontrol are an important target for advancing our knowledge on the etiology of drug abuse, intervening with the drug addiction process and developing novel treatments.

Dual-trait selection for ethanol consumption and withdrawal: genetic and transcriptional network effects

BACKGROUND

Data from C57BL/6J (B6) × DBA/2J (D2) F2 intercrosses (B6xD2 F2 ), standard and recombinant inbred strains, and heterogeneous stock mice indicate that a reciprocal (or inverse) genetic relationship exists between alcohol consumption and withdrawal severity. Furthermore, some genetic studies have detected reciprocal quantitative trait loci (QTLs) for these traits. We used a novel mouse model developed by simultaneous selection for both high alcohol consumption/low withdrawal and low alcohol consumption/high withdrawal and analyzed the gene expression and genome-wide genotypic differences.

METHODS

Randomly chosen third selected generation (S3 ) mice (N = 24/sex/line), bred from a B6xD2 F2 , were genotyped using the Mouse Universal Genotyping Array, which provided 2,760 informative markers. QTL analysis used a marker-by-marker strategy with the threshold for a significant log of the odds (LOD) set at 10. Gene expression in the ventral striatum was measured using the Illumina Mouse 8.2 array. Differential gene expression and the weighted gene co-expression network analysis (WGCNA) were implemented.

RESULTS

Significant QTLs for consumption/withdrawal were detected on chromosomes (Chr) 2, 4, 9, and 12. A suggestive QTL mapped to Chr 6. Some of the QTLs overlapped with known QTLs mapped for 1 of the traits individually. One thousand seven hundred and forty-five transcripts were detected as being differentially expressed between the lines; there was some overlap with known withdrawal genes (e.g., Mpdz) located within QTL regions. WGCNA revealed several modules of co-expressed genes showing significant effects in both differential expression and intramodular connectivity; a module richly annotated with kinase-related annotations was most affected.

CONCLUSIONS

Marked effects of selection on expression and network structure were detected. QTLs overlapping with differentially expressed genes on Chr 2 (distal) and 4 suggest that these are cis-eQTLs (Chr 2: Kif3b, Kcnq2; Chr 4: Mpdz, Snapc3). Other QTLs identified were on Chr 2 (proximal), 9, and 12. Network results point to involvement of kinase-related mechanisms and outline the need for further efforts such as interrogation of noncoding RNAs.

Cytokines and chemokines as biomarkers of ethanol-induced neuroinflammation and anxiety-related behavior: role of TLR4 and TLR2

Recent evidence supports the influence of neuroimmune system activation on behavior. We have demonstrated that ethanol activates the innate immune system by stimulating toll-like receptor 4 (TLR4) signaling in glial cells, which triggers the release of inflammatory mediators and causes neuroinflammation. The present study aimed to evaluate whether the ethanol-induced up-regulation of cytokines and chemokines is associated with anxiety-related behavior, 24 h after ethanol removal, and if TLR4 or TLR2 is involved in these effects. We used WT, TLR4-KO and TLR2-KO mice treated with alcohol for 5 months to show that chronic ethanol consumption increases the levels of cytokines (IL-1β, IL-17, TNF-α) and chemokines (MCP-1, MIP-1α, CX3CL1) in the striatum and serum (MCP-1, MIP-1α, CX3CL1) of WT mice. Alcohol deprivation for 24 h induces IFN-γ levels in the striatum and maintains high levels of some cytokines (IL-1β, IL-17) and chemokines (MIP-1α, CX3CL1) in this brain region. The latter events were associated with an increase in anxiogenic-related behavior, as evaluated by the dark and light box and the elevated plus maze tests. Notably, mice lacking TLR4 or TLR2 receptors are largely protected against ethanol-induced cytokine and chemokine release, and behavioral associated effects during alcohol abstinence. These data support the role of TLR4 and TLR2 responses in neuroinflammation and in anxiogenic-related behavior effects during ethanol deprivation, and also provide evidence that chemokines and cytokines can be biomarkers of ethanol-induced neuroimmune response.

Effects of stress, acute alcohol treatment, or both on pre-pulse inhibition in high- and low-alcohol preferring mice

Pre-pulse inhibition of the acoustic startle reflex (PPI) is a measure of sensorimotor gating frequently used to assess information processing in both humans and rodents. Both alcohol and stress exposure can modulate PPI, making it possible to assess how stress and alcohol interact to influence information processing. Humans with an increased genetic risk for alcoholism are more reactive to stressful situations compared to those without a family history, and alcohol may have stress-dampening effects for those with high genetic risk. The purpose of the present study was to examine the effects of stress, acute alcohol exposure, or both on PPI in male and female mice selectively bred for high- (HAP2) and low- (LAP2) alcohol preference. Experiment 1 assessed the effects of various doses of acute alcohol on PPI. Experiments 2 and 3 assessed the effect of 10 days of restraint stress on subsequent PPI tested at 30 min (Experiment 2) or 24 h (Experiment 3) following the termination of stress exposure. Experiment 3 also examined the effects of acute alcohol treatment (0.75 g/kg) on PPI in mice previously exposed to stress or no stress. Results indicate that 0.75 and 1.0 g/kg doses of alcohol increased PPI in HAP2 but not LAP2 mice. When PPI was tested 30 min after stress exposure, stressed HAP2 mice showed a trend toward decreased PPI and stressed LAP2 mice showed a trend toward increased PPI. The combination of stress and alcohol treatment did not alter PPI in either line 24 h following the termination of stress exposure, suggesting that alcohol does not ameliorate the effect of stress on PPI. Stressed LAP2 mice had increased basal circulating corticosterone on the final stress exposure day compared to non-stressed LAP2 mice, and no difference was found between stressed and non-stressed HAP2 mice. The results suggest that high genetic risk for alcoholism may be related to increased sensitivity to alcohol and stress effects on PPI, and this sensitivity could signify an endophenotype for increased genetic risk to develop alcoholism.

Ethanol drinking in withdrawal seizure-prone and -resistant selected mouse lines

Withdrawal Seizure-Prone (WSP) and Withdrawal Seizure-Resistant (WSR) mouse lines were bidirectionally selectively bred, respectively, to have severe or mild ethanol withdrawal handling-induced convulsions (HICs) after cessation of 3 days of ethanol vapor inhalation. Murine genotypes with severe withdrawal have been found to show low ethanol consumption, and high consumers show low withdrawal. An early drinking study with WSP and WSR mice showed modest evidence consistent with this genetic correlation, but there were several limitations to that experiment. We therefore conducted a thorough assessment of two bottle ethanol preference drinking in both replicate pairs of WSP/WSR selected lines in mice of both sexes. Greater preference drinking of WSR-2 than WSP-2 female mice confirmed the earlier report. However, in the parallel set of selected lines, the WSP-1 mice drank more than the WSR-1s. Naive mice tested for preference for sucrose, saccharin and quinine did not differ markedly for any tastant. Finally, in a test of binge-like drinking, Drinking in the Dark (DID), WSP mice drank more than WSR mice and attained significantly higher (but still modest) blood ethanol concentrations. Tests of acute withdrawal after DID showed a mild, but significant elevation in handling-induced convulsions in the WSP line. These results provide further evidence that 2-bottle ethanol preference and DID are genetically distinguishable traits.

Reduced emotional signs of opiate withdrawal in rats selectively bred for low (LoS) versus high (HiS) saccharin intake

RATIONALE

Rats bred for high (HiS) and low (LoS) saccharin intake exhibit divergent behavioral responses to multiple drugs of abuse, with HiS rats displaying greater vulnerability to drug taking. Previous research indicates that this effect may be due to increased sensitivity to reward in HiS rats and to the aversive effects of acute drug administration in LoS rats.

OBJECTIVE

The current study investigated whether HiS and LoS rats also exhibit different behavioral signs of withdrawal following one or repeated opiate exposures.

METHODS

Emotional signs of opiate withdrawal were assessed with potentiation of the acoustic startle reflex and conditioned place aversion (CPA) in male and female HiS and LoS rats. Startle was measured before and 4 h after a 10-mg/kg injection of morphine on days 1, 2, and 7 of opiate exposure. CPA was induced with a 2-day, naloxone-precipitated conditioning paradigm. Somatic signs of withdrawal and weight loss were also measured.

RESULTS

Male and female LoS rats exhibited lower startle potentiation than HiS rats on the seventh day of morphine exposure. LoS male rats also failed to develop a CPA to morphine withdrawal. No differences in physical withdrawal signs were observed between HiS and LoS rats, but males of both lines had more physical signs of withdrawal than females.

CONCLUSIONS

These results suggest that LoS rats are less vulnerable to the negative emotional effects of morphine withdrawal than HiS rats. A less severe withdrawal syndrome may contribute to decreased levels of drug taking in the LoS line.

Genotype modulates age-related alterations in sensitivity to the aversive effects of ethanol: an eight inbred strain analysis of conditioned taste aversion

Adolescent individuals display altered behavioral sensitivity to ethanol, which may contribute to the increased ethanol consumption seen in this age-group. However, genetics also exert considerable influence on both ethanol intake and sensitivity. Currently there is little research assessing the combined influence of developmental and genetic alcohol sensitivities. Sensitivity to the aversive effects of ethanol using a conditioned taste aversion (CTA) procedure was measured during both adolescence (P30) and adulthood (P75) in eight inbred mouse strains (C57BL/6J, DBA/2J, 129S1/SvImJ, A/J, BALB/cByJ, BTBR T(+) tf/J, C3H/HeJ and FVB/NJ). Adolescent and adult mice were water deprived, and subsequently provided with access to 0.9% (v/v) NaCl solution for 1 h. Immediately following access mice were administered ethanol (0, 1.5, 2.25 and 3 g/kg, ip). This procedure was repeated in 72 h intervals for a total of five CTA trials. Sensitivity to the aversive effects of ethanol was highly dependent upon both strain and age. Within an inbred strain, adolescent animals were consistently less sensitive to the aversive effects of ethanol than their adult counterparts. However, the dose of ethanol required to produce an aversion response differed as a function of both age and strain.

Ethanol tolerance and withdrawal severity in high drinking in the dark selectively bred mice

BACKGROUND

Mouse lines are being selectively bred in replicate for high blood ethanol concentrations (BECs) achieved after limited access of ethanol (EtOH) drinking early in the circadian dark phase. High Drinking in the Dark-1 (HDID-1) mice are in selected generation S21, and the replicate HDID-2 line in generation S14. Tolerance and withdrawal symptoms are 2 of the 7 diagnostic criteria for alcohol dependence. Withdrawal severity has been found in mouse studies to be negatively genetically correlated with EtOH preference drinking.

METHODS

To determine other traits genetically correlated with high DID, we compared naïve animals from both lines with the unselected, segregating progenitor stock, HS/Npt. Differences between HDID-1 and HS would imply commonality of genetic influences on DID and these traits.

RESULTS

Female HDID-1 and HDID-2 mice tended to develop less tolerance than HS to EtOH hypothermia after their third daily injection. A trend toward greater tolerance was seen in the HDID males. HDID-1, HDID-2, and control HS lines did not differ in the severity of acute or chronic withdrawal from EtOH as indexed by the handling-induced convulsion (HIC). Both HDID-1 and HDID-2 mice tended to have greater HIC scores than HS regardless of drug treatment.

CONCLUSIONS

These results show that tolerance to EtOH's hypothermic effects may share some common genetic control with reaching high BECs after DID, a finding consistent with other data regarding genetic contributions to EtOH responses. Withdrawal severity was not negatively genetically correlated with DID, unlike its correlation with preference drinking, underscoring the genetic differences between preference drinking and DID. HDID lines showed greater basal HIC scores than HS, suggestive of greater central nervous system excitability.

Effects of cross-fostering on alcohol preference and correlated responses to selection in high- and low-alcohol-preferring mice

BACKGROUND

Selectively bred rodent lines are valuable tools for investigating gene × environment interactions related to risk for alcoholism in humans. Early maternal environment is one particular factor known for critically influencing neural, hormonal, and behavioral outcomes in adulthood. Cross-fostering is a procedure that may be used to explore the role of genotype-dependent maternal influences on phenotypic variability in adulthood. The purpose of these experiments was to examine the effects of cross-fostering on free-choice alcohol drinking and correlated responses to selection for alcohol preference in mice selectively bred for high (HAP2) and low (LAP2) alcohol preference.

METHODS

Mice were assigned to one of the following treatments: SHAM (pups that were fostered to their original biological mother), IN (pups that were fostered to a different mother of the same line), and CROSS (pups that were fostered to a mother of a different line). Mice were tested in adulthood for (i) free 24-hour access to alcohol for a period of 28 days; (ii) the expression of the acoustic startle response and fear-potentiated startle (FPS); and (iii) handling-induced convulsions (HICs) during acute alcohol withdrawal.

RESULTS

Overall, the expression of the alcohol preference selection phenotype was robust in all groups (HAP2 > LAP2). Cross-fostering produced a moderate but significant reduction in g/kg alcohol drinking and preference scores in HAP2 mice (CROSS < SHAM) but had no effect in LAP2 mice. Cross-fostering did not affect the expression of correlated responses to selection: acoustic startle response (HAP2 > LAP2), FPS (HAP2 > LAP2), HICs (LAP2 > HAP2).

CONCLUSIONS

It appears that maternal environment can modify the expression of the high-alcohol-preference phenotype in HAP2 selectively bred mice. These results suggest a gene × environment interaction with respect to the expression of the high-alcohol-preference selection phenotype but not correlated responses to selection.

The negative effects of alcohol hangover on high-anxiety phenotype rats are influenced by the glutamate receptors of the dorsal midbrain

Alcoholism is a chronic disorder characterized by the appearance of a withdrawal syndrome following the abrupt cessation of alcohol intake that includes symptoms of physical and emotional disturbances, anxiety being the most prevalent symptom. In humans, it was shown that anxiety may increase the probability of relapse. In laboratory animals, however, the use of anxiety to predict alcohol preference has remained difficult. Excitatory amino acids as glutamate have been implicated in alcohol hangover and may be responsible for the seizures and anxiety observed during withdrawal. The dorsal periaqueductal gray (DPAG) is a midbrain region critical for the modulation/expression of anxiety- and fear-related behaviors and the propagation of seizures induced by alcohol withdrawal, the glutamate neurotransmission being one of the most affected. The present study was designed to evaluate whether low- (LA) and high-anxiety rats (HA), tested during the alcohol hangover phase, in which anxiety is the most prevalent symptom, are more sensitive to the reinforcing effects of alcohol when tested in a voluntary alcohol drinking procedure. Additionally, we were interested in investigating the main effects of reducing the excitatory tonus of the dorsal midbrain, after the blockade of the ionotropic glutamate receptors into the DPAG, on the voluntary alcohol intake of HA and LA motivated rats that were made previously experienced with the free operant response of alcohol drinking. For this purpose, we used local infusions of the N-metil D-Aspartato (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-kainate receptors antagonist DL-2-Amino-7-phosphonoheptanoic acid - DL-AP7 (10 nmol/0.2 μl) and l-glutamic acid diethyl ester - GDEE (160 nmol/0.2 μl), respectively. Alcohol intoxication was produced by 10 daily bolus intraperitonial (IP) injections of alcohol (2.0 g/kg). Peak-blood alcohol levels were determined by gas-chromatography analysis in order to assess blood-alcohol content. Unconditioned and conditioned anxiety-like behavior was assessed by the use of the fear-potentiated startle procedure (FPS). Data collected showed that anxiety and alcohol drinking in HA animals are positively correlated in animals that were made previously familiarized with the anxiolytic effects of alcohol. In addition, anxiety-like behavior induced during alcohol hangover seems to be an effect of changes in glutamatergic neurotransmission into DPAG possibly involving AMPA/kainate and NMDA receptors, among others.

Food dependence in rats selectively bred for low versus high saccharin intake. Implications for "food addiction"

The "food addiction" concept implies that proneness to drug dependence and to food dependence should covary. The latter was studied in low- (LoS) and high- (HiS) saccharin-consuming rats, who differ in drug self-administration (HiS>LoS) and withdrawal (LoS>HiS). Sugary food intake in the first 1-2 h was higher in HiS than LoS rats. Sugar intake predicted startle during abstinence only among LoS rats. These results may suggest bingeing-proneness in HiS rats and withdrawal-proneness among LoS rats. However, intake escalation and somatic withdrawal did not differ between lines. Further study with selectively bred rats, with attention to definitions and measures, is warranted.

Development of ethanol withdrawal-related sensitization and relapse drinking in mice selected for high- or low-ethanol preference

BACKGROUND

Previous studies have shown that high alcohol consumption is associated with low withdrawal susceptibility, while at the same time, other studies have shown that exposure to ethanol vapor increases alcohol drinking in rats and mice. In the present studies, we sought to shed light on this seeming contradiction using mice selectively bred for High- (HAP) and Low- (LAP) Alcohol Preference, first, assessing these lines for differences in signs of ethanol withdrawal and second, for differences in the efficacy of intermittent alcohol vapor exposure on elevating subsequent ethanol intake.

METHODS

Experiment 1 examined whether these lines of mice differed in ethanol withdrawal-induced CNS hyperexcitability and the development of sensitization to this effect following intermittent ethanol vapor exposure. Adult HAP and LAP lines (replicates 1 and 2), and the C3H/HeNcr inbred strain (included as a control genotype for comparison purposes) received intermittent exposure to ethanol vapor and were evaluated for ethanol withdrawal-induced seizures assessed by scoring handling-induced convulsions (HIC). Experiment 2 examined the influence of chronic intermittent ethanol exposure on voluntary ethanol drinking. Adult male and female HAP-2 and LAP-2 mice, along with male C57BL/6J (included as comparative controls) were trained to drink 10% ethanol using a limited access (2 h/d) 2-bottle choice paradigm. After stable baseline daily intake was established, mice received chronic intermittent ethanol vapor exposure in inhalation chambers. Ethanol intake sessions resumed 72 hours after final ethanol (or air) exposure for 5 consecutive days.

RESULTS

Following chronic ethanol treatment, LAP mice exhibited overall greater withdrawal seizure activity compared with HAP mice. In Experiment 2, chronic ethanol exposure/withdrawal resulted in a significant increase in ethanol intake in male C57BL/6J, and modestly elevated intake in HAP-2 male mice. Ethanol intake for male control mice did not change from baseline levels of intake. In contrast, HAP-2 female and LAP-2 mice of both sexes did not show changes in ethanol intake as a consequence of intermittent ethanol exposure.

CONCLUSIONS

Overall, these results indicate that the magnitude of ethanol withdrawal-related seizures is inversely related to inherited ethanol intake preference. Additionally, intermittent ethanol vapor exposure appears more likely to affect high-drinking mice (C57BL/6J and HAP-2) than low drinkers, although these animals are less affected by ethanol withdrawal.

Ontogeny of ethanol intake in alcohol preferring (P) and alcohol nonpreferring (NP) rats

There is a scarcity of research on ethanol affinity in alcohol-preferring (P) rats before weaning and it is unknown if neonate P rats exhibit ethanol intake preferences comparable to those observed in adult P rats. This study examined ethanol intake in P and alcohol-nonpreferring (NP) rats 3 hr after birth (Experiment 1, surrogate nipple test), at postnatal days (PD) 8, 12, and 18 (Experiment 2, consumption from the floor procedure) and at adolescence (Experiment 3, two-bottle choice test at PD32). The high-preference genotype was readily expressed 3 hr after birth. P neonates drank twice as much ethanol as their NP counterparts. This heightened ethanol preference transiently reversed at P8, reemerged as weaning approached (P18) and was fully expressed during adolescence. These results help to clarify the ontogeny of genetic predisposition for ethanol. Genetic predisposition for higher ethanol intake in P than in NP rats seems to be present immediately following birth.

What aspects of human alcohol use disorders can be modeled using selectively bred rat lines?

The use of selective breeding to produce animal models for the study of alcohol abuse and alcoholism represents one of the major advances in the field of alcohol research. Rats selectively bred for alcohol preference and alcohol nonpreference have been useful to both preclinical and clinical investigators in the alcohol research community for studying the behavioral, neurobiological, and molecular basis of alcohol drinking, for identifying the genes that may contribute to the development of alcohol abuse and alcoholism, and for evaluating the utility of drugs aimed at reducing alcohol intake and preventing alcohol relapse. Rats selectively bred for alcohol preference (alcohol preferring or "P" line) have enhanced responsiveness to the low dose reinforcing effects of alcohol, less aversion to moderate/high doses of alcohol, and are able to develop tolerance to the aversive effects of alcohol more rapidly and to maintain tolerance longer than rats selectively bred for alcohol nonpreference (alcohol nonpreferring or "NP" line). The increased potency of low-dose alcohol as a reinforcer for P rats might be expected to foster and maintain alcohol drinking. Weaker aversion to the pharmacological effects of moderate/high doses of alcohol in the P line would allow P rats to drink more alcohol than NP rats before the postingestional effects become aversive. Rapid induction of tolerance to the aversive effects of alcohol with repeated bouts of voluntary alcohol drinking, as well as persistence of alcohol tolerance in rats of the P line might serve to maintain alcohol drinking. These are powerful mechanisms that may serve to promote and maintain a high alcohol drinking behavior. Although these rat lines have been used to address several characteristics of excessive alcohol consumption in humans, they have not yet been used to model several aspects of human alcohol use disorders. New applications of these selectively bred rat lines are discussed which may further our understanding of the factors contributing to alcohol abuse and alcoholism.

Pentylenetetrazol produces a state-dependent conditioned place aversion to alcohol withdrawal in mice

The purpose of this study was to determine if aversive effects of alcohol withdrawal could be detected in mice using the place conditioning procedure and whether the GABA(A) receptor antagonist, pentylenetetrazol (PTZ), would increase the aversive effects of alcohol withdrawal and increase the probability of detecting conditioned place aversion. Subjects were alcohol-naïve mice from a specific line selectively bred for low alcohol preference (LAP1; n=91) and were assigned to three groups: alcohol withdrawal, PTZ alone, and PTZ+alcohol withdrawal. On four trials, mice received either a 4.0 g/kg intraperitoneal (i.p.) injection of alcohol (alcohol withdrawal, PTZ+alcohol withdrawal groups) or saline (PTZ group) 8 h prior to being placed on a distinctive floor texture for a 30-min conditioning session. Five minutes before these sessions, mice in the PTZ and PTZ+alcohol withdrawal groups received PTZ (5.0 mg/kg; i.p.) and the alcohol withdrawal group received saline. On intervening days mice received two saline injections at the same time points prior to being placed on a different floor texture. Post-conditioning floor preference was assessed in two 60-min tests; the first test was drug-free and the second test was state-dependent. Neither alcohol withdrawal nor PTZ produced significant place conditioning. The PTZ+alcohol withdrawal group showed a significant place aversion during the state-dependent test. These data suggest that the combined stimulus properties of PTZ and alcohol withdrawal facilitated the expression of conditioned place aversion to alcohol withdrawal.

Modeling risk factors for nicotine and other drug abuse in the preclinical laboratory

Risk factors that predict vulnerability for nicotine and other drug abuse have been identified using preclinical models, and there is close agreement with clinical and epidemiological studies. The major risk factors to be discussed are age, sex/hormonal status, impulsivity, sweet-liking, novelty reactivity, proclivity for exercise, and environmental impoverishment (vs. enrichment). This discussion will focus on factors that preclinical research has determined are strong and translatable predictors of nicotine and other drug abuse. An advantage of using preclinical models is that prospective, longitudinal studies and within-subject designs can be used to reveal risk factors that are diverse yet maintain unique characteristics. The many interrelationships among these factors lead to an additive vulnerability that increases the predictability that drug abuse will occur. A feature that these risk factors have in common is that they consistently predict vulnerability to drug abuse over critical transition phases of addiction that are difficult to examine prospectively in humans, such as acquisition, escalation, and reinstatement of drug-seeking after abstinence (relapse). The models offer valuable information that has been transferred to effective prevention and treatment strategies for smoking and other drug abuse in humans.

Detection of reciprocal quantitative trait loci for acute ethanol withdrawal and ethanol consumption in heterogeneous stock mice

RATIONALE

Previous studies have suggested that there is an inverse genetic relationship between ethanol consumption (two-bottle choice, continuous access) and ethanol withdrawal (e.g., Metten et al., Behav Brain Res 95:113-122, 1998a).

OBJECTIVES

The current study used short-term selective breeding from heterogeneous stock (HS) animals to examine this relationship. The primary goal of the current study was to determine if reciprocal quantitative trait loci (QTLs) could be found in the selectively bred lines. The advantage of detecting QTLs in HS animals is that it is possible to extract a haplotype signature for the QTL, which in turn can be used to narrow the number of candidate genes generated from gene expression and sequence databases (see, e.g., Hitzemann et al., Mamm Genome 14:733-747, 2003).

RESULTS

Seven reciprocal QTLs were detected on chromosomes (Chr) 1 (two), 3, 6, 11, 16, and 17 that exceeded the nominal LOD threshold of 10; genetic drift, which occurs during selection, dramatically increases the LOD threshold. The proximal Chr 1 QTL was examined in some detail. The haplotype structure of the QTL was such that the LP/J allele was associated with low withdrawal and high consumption. The QTL appears to be located in a gene-poor region between 170 and 173 Mbp. Based on available sequence data, two plausible candidate genes emerge-Nos1ap and Atf6alpha.

CONCLUSIONS

The data presented here confirm some aspects of the negative genetic relationship between acute ethanol withdrawal and ethanol consumption. The QTL data point to the potential involvement of NO signaling and/or the unfolded protein response.

Effects of forced alcohol drinking on alcohol-water choice in three pairs of rat lines selectively bred for differences in alcohol preference

Three pairs of Indiana University rat lines (inbred alcohol-preferring and nonpreferring rat lines [P/NPs], high- and low-alcohol-drinking rat lines [HAD/LAD1s and HAD/LAD2s]) were bred in the School of Medicine colony to drink high versus low daily amounts of a 10% vol/vol alcohol test solution (>5.0 g/kg body weight vs. <1.5 g/kg body weight), and a high versus low proportion of alcohol to water (>2:1 vs. <0.5:1) by the end of a 3-week alcohol-water choice condition. This choice phase was always preceded by four days of a forcing procedure with alcohol as the only fluid. The present study examined the contribution of the forcing procedure to the alcohol intake of animals in each pair of lines by comparing daily alcohol intake of rats housed in experimental chambers in a forced group (4 days with only alcohol solution to drink followed by 22 choice days) versus a choice group (both alcohol and water available all 26 days). As expected, under the initial alcohol exposure, high-drinking line rats drank more alcohol than low-drinking line rats, and all forced groups drank more alcohol than choice groups. At the start of the choice phase, all low-drinking line forced groups immediately dropped their alcohol intake to the level of their choice groups. In contrast, all high-drinking line forced groups maintained a high level of alcohol intake under choice, whereas all high-drinking line choice groups slowly increased average alcohol intake across the 22-day choice phase, ending near the average intake of their forced groups. However, a small subset of each high-drinking line choice animals failed to increase alcohol intake until subsequently forced with alcohol for 4 days and tested again in choice. These results indicate that the alcohol-forcing procedure used in deriving these lines resulted in the selection of more than one pathway to a high-drinking phenotype. In addition, high-drinking line animals appeared more sensitive to the differences between laboratory- and colony-testing environments than low-drinking line animals. These data suggest that these high-drinking lines may represent an unexpectedly appropriate complex model of how multiple factors may contribute to the genesis of human alcoholism.

Genetic correlates of morphine withdrawal in 14 inbred mouse strains

Male mice from 14 standard inbred strains were exposed to morphine in a sustained released preparation injected subcutaneously. Five hours later withdrawal was precipitated by intraperitoneal injection of naloxone. Mice were tested from 0 to 15 min after naloxone for withdrawal jumping behavior, and then from minute 15-16 for other signs, including boli count, presence of soft stool, lacrimation, "wet dog" shakes, and air chewing. They were also assessed for change in body temperature 17 min after naloxone. Strains differed markedly in the severity of withdrawal for jumping, change in body temperature, and number of fecal boli. Strains also differed in percentage of animals displaying soft stool and air chewing behavior. The other two signs were seen at too low frequency for analysis. Correlations of strain mean withdrawal severity with other responses to morphine and other abused drugs showed that high morphine withdrawal jumping and low change in body temperature were both genetically related to high morphine consumption, but not generally to other measures of morphine withdrawal or morphine sensitivity.

Acoustic startle at baseline and during acute alcohol withdrawal in replicate mouse lines selectively bred for high or low alcohol preference

BACKGROUND

Previous data in both rat and mouse genetic models suggest that there is a genetic relationship between acute alcohol withdrawal responses and innate alcohol drinking behavior. The purpose of the present study was to examine whether acute alcohol withdrawal responses, as measured by acoustic startle and prepulse inhibition (PPI) of acoustic startle, may be genetically related to innate differences in alcohol preference in 2 mouse lines selectively bred for high (HAP1 and HAP2) or low (LAP1 and LAP2) alcohol preference. Line differences in startle responses at baseline, prior to alcohol or saline treatment, were also measured.

METHODS

Alcohol-naive, male and female HAP1 (n = 35) and LAP1 (n = 32) and HAP2 (n = 43) and LAP2 (n = 40) mice were tested under baseline conditions and during withdrawal from a single injection of 4.0 g/kg alcohol or equal volume of saline at 4, 8, and 12 hours post-injection.

RESULTS

On most trial types, baseline startle responses and PPI were greater in both HAP lines than in both LAP lines, and startle responses were greater in males than in females. During acute alcohol withdrawal, both male LAP lines, and LAP1 females, showed reduced startle responses at the 4-hour time point during acute alcohol withdrawal. In contrast, both HAP1 males and females showed a trend toward enhanced startle at 4 hours in withdrawal. No clear differences in PPI during withdrawal were evident.

CONCLUSIONS

These findings indicate good evidence for a genetic relationship between greater baseline acoustic startle responses and PPI and high alcohol preference. Modest support for a genetic correlation between low alcohol preference and reduced startle responses at 4 hours in withdrawal was found in male mice. The suppression in acoustic startle during acute alcohol withdrawal in male LAP lines but not in male HAP lines suggests that a genetic propensity toward low alcohol preference may be related to greater sensitivity to alcohol as measured by acoustic startle responses during acute alcohol withdrawal.

Manipulation of fatty acid amide hydrolase functional activity alters sensitivity and dependence to ethanol

The aim of this study was to examine the role of fatty acid amide hydrolase (FAAH) on ethanol sensitivity, preference, and dependence. The deletion of FAAH gene or the inhibition of FAAH by carbamoyl-biphenyl-3-yl-cyclohexylcarbamate (URB597) (0.1 mg/kg) markedly increased the preference for ethanol. The study further reveals that URB597 specifically acts through FAAH and that cannabinoid-1 (CB(1)) receptor is critical for N-arachidonoyl ethanolamide (AEA) mediated ethanol-reinforced behavior as revealed by lack of URB597 effect in both FAAH and CB(1)-/- mice compared with vehicle-treated -/- mice. The FAAH -/- mice displayed a lower sensitivity to hypothermic and sedative effects to acute ethanol challenge. The FAAH -/- mice also exhibited a reduction in the severity of handling-induced convulsions following withdrawal from chronic ethanol exposure. The CB(1) receptor and proenkephalin gene expressions, and CB(1) receptor and mu-opioid (MO) receptor-mediated G-protein activation were found to be significantly lower in the caudate-putamen, nucleus accumbens core and shell of FAAH -/- than +/+ mice. Interestingly, the MO receptor-stimulated G-protein signaling was greater in the striatum of FAAH -/- than +/+ mice following voluntary ethanol consumption. These findings suggest that an elevation in the AEA content and its action on the limbic CB(1) receptor and MO receptor might contribute to ethanol-reinforced behavior. Treatment with drugs that decrease AEA tone might prove useful in reducing excessive ethanol consumption.

Mouse inbred strain differences in ethanol drinking to intoxication

Recently, we described a simple procedure, Drinking in the Dark (DID), in which C57BL/6J mice self-administer ethanol to a blood ethanol concentration (BEC) above 1 mg/ml. The test consists of replacing the water with 20% ethanol in the home cage for 4 h early during the dark phase of the light/dark cycle. Three experiments were conducted to explore this high ethanol drinking model further. In experiment 1, a microanalysis of C57BL/6J behavior showed that the pattern of ethanol drinking was different from routine water intake. In experiment 2, drinking impaired performance of C57BL/6J on the accelerating rotarod and balance beam. In experiment 3, 12 inbred strains were screened to estimate genetic influences on DID and correlations with other traits. Large, reliable differences in intake and BEC were detected among the strains, with C57BL/6J showing the highest values. Strain means were positively correlated with intake and BEC in the standard (24 h) and a limited (4 h) two-bottle ethanol vs. water test, but BECs reached higher levels for DID. Strain mean correlations with other traits in the Mouse Phenome Project database supported previously reported genetic relationships of high ethanol drinking with low chronic ethanol withdrawal severity and low ethanol-conditioned taste aversion. We extend these findings by showing that the correlation estimates remain relatively unchanged even after correcting for phylogenetic relatedness among the strains, thus relaxing the assumption that the strain means are statistically independent. We discuss applications of the model for finding genes that predispose pharmacologically significant drinking in mice.

Neuropharmacology of the endocannabinoid signaling system-molecular mechanisms, biological actions and synaptic plasticity

The endocannabinoid signaling system is composed of the cannabinoid receptors; their endogenous ligands, the endocannabinoids; the enzymes that produce and inactivate the endocannabinoids; and the endocannabinoid transporters. The endocannabinoids are a new family of lipidic signal mediators, which includes amides, esters, and ethers of long-chain polyunsaturated fatty acids. Endocannabinoids signal through the same cell surface receptors that are targeted by Delta(9)-tetrahydrocannabinol (Delta(9)THC), the active principles of cannabis sativa preparations like hashish and marijuana. The biosynthetic pathways for the synthesis and release of endocannabinoids are still rather uncertain. Unlike neurotransmitter molecules that are typically held in vesicles before synaptic release, endocannabinoids are synthesized on demand within the plasma membrane. Once released, they travel in a retrograde direction and transiently suppress presynaptic neurotransmitter release through activation of cannabinoid receptors. The endocannabinoid signaling system is being found to be involved in an increasing number of pathological conditions. In the brain, endocannabinoid signaling is mostly inhibitory and suggests a role for cannabinoids as therapeutic agents in central nervous system (CNS) disease. Their ability to modulate synaptic efficacy has a wide range of functional consequences and provides unique therapeutic possibilities. The present review is focused on new information regarding the endocannabinoid signaling system in the brain. First, the structure, anatomical distribution, and signal transduction mechanisms of cannabinoid receptors are described. Second, the synthetic pathways of endocannabinoids are discussed, along with the putative mechanisms of their release, uptake, and degradation. Finally, the role of the endocannabinoid signaling system in the CNS and its potential as a therapeutic target in various CNS disease conditions, including alcoholism, are discussed.

Acoustic Startle Reactivity During Acute Alcohol Withdrawal in Rats That Differ in Genetic Predisposition Toward Alcohol Drinking: Effect of Stimulus Characteristics

BACKGROUND

We have previously reported an association between greater alcohol withdrawal magnitude after a single alcohol exposure and a genetic predisposition toward low alcohol drinking in rats selectively bred for differences in alcohol intake when acoustic startle reactivity to a tone stimulus was used to index acute alcohol withdrawal. The purpose of this study was to examine whether the quality of the acoustic startle stimulus (noise versus tone) is important for detecting a genetic relationship between alcohol withdrawal magnitude and alcohol drinking behavior.

METHODS

Alcohol-naive male rats selectively bred for high alcohol intake [alcohol-preferring (P), high-alcohol-drinking (HAD)1, and HAD2] or low alcohol intake [alcohol-nonpreferring (NP), low-alcohol-drinking (LAD)1, and LAD2] received a single intragastric infusion of water or alcohol (4.0 g/20.3 ml/kg; 25% v/v), and acoustic startle test sessions were given at 14, 16, 18, 20, and 24 hr after infusion. Each test session consisted of a 5-min acclimation period followed by random presentation of various white noise stimuli (90, 100, 110, and 120 dB.)

RESULTS

Line differences in acoustic startle magnitude under control conditions were present in all three pairs of selectively bred lines; P rats showed a greater startle magnitude relative to NP rats, whereas both LAD lines showed a greater startle magnitude relative to both HAD lines. During alcohol withdrawal, the P, HAD1, and HAD2 lines showed enhanced startle magnitude compared with their water-treated controls. No change in startle magnitude during alcohol withdrawal was found in the NP, LAD1, or LAD2 lines.

CONCLUSIONS

In contrast to our prior findings, these results showed a genetic association between high alcohol drinking and a greater startle response magnitude to a noise stimulus during alcohol withdrawal. It seems that the genetic association between alcohol drinking and alcohol withdrawal, as assessed by the acoustic startle response, depends on the quality of the acoustic startle stimulus.

Decreased reward during acute alcohol withdrawal in rats selectively bred for low alcohol drinking

We have previously hypothesized that increased sensitivity to the dysphoric-like or aversive effects of alcohol withdrawal following an initial exposure to alcohol might be associated with a genetic propensity to avoid alcohol. A decrease in brain reward function, as measured by an elevation in intracranial self-stimulation (ICSS) reward threshold, is one of the few methods available to model dysphoric-like or aversive effects of drug withdrawal in rats. We compared brain reward function during withdrawal following an initial exposure to alcohol in alcohol-naïve rats selectively bred for high (HAD1 line) versus low (LAD1 line) voluntary alcohol consumption. Male HAD1 (n=5) and LAD1 (n=6) rats were implanted with unilateral electrodes in the medial forebrain bundle and trained to bar press for delivery of a 100 microA current that varied in frequency from 45 to 200 Hz. Responding for ICSS was generally stable within subjects across multiple experimental sessions on a given day and across several consecutive days prior to alcohol or water administration. ICSS responding was assessed in both rat lines prior to and at 12, 14, 16, 18, 20, and 24 h following a single intragastric infusion of alcohol (4.0 g/kg body weight) or water. Rats of the LAD1 line, but not those of the HAD1 line, exhibited a decrease in brain reward function as evidenced by a decrease in bar-press responding for ICSS and an increase in ICSS stimulation threshold during alcohol withdrawal. The results suggest that rats selectively bred for low alcohol drinking may experience dysphoric-like effects during withdrawal from an initial exposure to alcohol, while rats selectively bred for high alcohol drinking may not.

Increased ethanol consumption and preference and decreased ethanol sensitivity in female FAAH knockout mice

Previous studies have shown that mice lacking cannabinoid (CB1) receptor gene consume markedly reduced levels of ethanol. Mice lacking the enzyme fatty acid amidohydrolase (FAAH) are severely impaired in their ability to degrade anandamide (AEA) and therefore represent a unique animal model in which to examine the function of AEA in vivo on ethanol-drinking behavior. In the current study, FAAH(-/-) mice were tested for ethanol, saccharin or quinine consumption and preference. Ethanol-induced hypothermia, and sleep time were used to evaluate the sensitivity to acute effects of ethanol. Ethanol intake and preference were increased only in female FAAH(-/-) mice. No significant difference in saccharin or quinine consumption or preference was observed between genotypes. Female FAAH(-/-) mice were less sensitive to the hypothermic and sedative/hypnotic effects of acute ethanol. Supersensitivity to exogenous AEA was noted in both male and female FAAH(-/-) mice. Following voluntary ethanol consumption, CB1 receptor levels and function were down-regulated in male FAAH(+/+), FAAH(-/-), and female FAAH(+/+) mice but not in female FAAH(-/-) mice. Our results suggest that absence of an effect in male mice indicates a sex-linked mechanism that is secondary (or modulatory) to FAAH function. Thus, the data suggest that FAAH may be indirectly related to ethanol intake and sensitivity and central endocannabinoidergic-mediated pathways may regulate ethanol consumption.

Ethanol withdrawal and proclivity are inversely related in rats selectively bred for differential saccharin intake

Withdrawal severity and voluntary alcohol consumption are inversely related in rats and mice. The present study demonstrated this empirical relation and extended it in two ways. First, the rats were selectively bred for low (LoS) and high (HiS) saccharin intake, a phenotype that correlates positively with ethanol intake and inversely with emotional reactivity. Withdrawal has not yet been studied in these rats. Second, proclivity to consume ethanol was measured as conditioned preference for an ethanol-paired flavor. After 2 weeks of forced exposure to ethanol and a period of abstinence, LoS rats showed elevated acoustic startle; HiS rats did not (Exp. 1). When ethanol- and no-ethanol solutions were available freely during conditioning, both LoS and HiS rats preferred a flavor paired with 4% ethanol, but only HiS rats preferred a flavor paired with 10% ethanol (Exp. 2A); when exposure to the two solutions was controlled, all groups except LoS males preferred flavors paired with 4% or 10% ethanol (Exp. 2B). Thus, as predicted, withdrawal was more severe in the line with less ethanol proclivity (LoS). These results implicate basic associative and affective processes in individual differences in patterns of alcohol use.

Effects of chronic alcohol treatment on acoustic startle reactivity during withdrawal and subsequent alcohol intake in high and low alcohol drinking rats

AIMS

The purpose of the present study is to determine whether the inverse genetic association between alcohol withdrawal magnitude and genetic propensity for alcohol drinking that we have previously identified in alcohol-naive rats given alcohol acutely, would also be seen following chronic alcohol exposure. The effect of forced, chronic alcohol treatment on subsequent voluntary alcohol drinking was also examined.

METHODS

Male rats from the high alcohol drinking (HAD2) and low alcohol drinking (LAD2) lines received two intragastric (IG) infusions of alcohol (3.0 g/kg BW; 25% v/v) or an equal volume of water, separated by 5 h, every day for 20 consecutive days (chronic alcohol treatment). Acoustic startle reactivity was assessed at 10, 14, and 18 h after the second infusion on days 1, 5, 10, 15, and 20. After acoustic startle testing was completed, all rats received two IG infusions of 3.0 g alcohol/kg BW, separated by 5 h, and blood alcohol content was assessed at 10, 14, and 18 h after the second alcohol infusion. All rats were then given a 24 h free-choice between alcohol and water for 8 weeks.

RESULTS

Startle magnitude to a 120 dB tone was suppressed during alcohol withdrawal in both alcohol-treated HAD2 and LAD2 rats after 5, 10, and 15 days of alcohol treatment. Forced, chronic alcohol treatment produced metabolic tolerance in both the HAD2 and LAD2 lines and significantly suppressed subsequent voluntary alcohol intake in rats of the HAD2 line.

CONCLUSIONS

Reduced acoustic startle reactivity during alcohol withdrawal in both HAD2 and LAD2 rats is consistent with our previous findings in the HAD2 but not the LAD2 line and may reflect reduced CNS excitability during withdrawal from forced alcohol exposure. Forced alcohol exposure robustly retarded the expression of a genetic predisposition toward alcohol drinking in rats selectively bred for high alcohol intake.

Decreased alcohol self-administration and increased alcohol sensitivity and withdrawal in CB1 receptor knockout mice

Recent advances in the understanding of the neurobiological basis of alcohol dependence suggest that the endocannabinoid system may play a key role in the reinforcing effects of ethanol. In the present study, disruption of CB1 receptors in mice generated on a CD1 background decreased both ethanol consumption and preference. This decreased ethanol self-administration was associated with increased sensitivity to the acute intoxicating effects of ethanol. Mutant mice were more sensitive to the hypothermic and sedative/hypnotic effects of acute ethanol administration (1.5-4.0 g/kg), although plasma ethanol concentrations did not differ from those of controls. Moreover, wild-type mice exhibited normal locomotor activation caused by 1.0-2.5 g/kg injection of ethanol, whereas mutant mice displayed sedation in response to the injection of the same ethanol doses. The severity of alcohol withdrawal-induced convulsions was also increased in CB1(-/-) mice. Our results suggest that CB1 receptors participate in the regulation of ethanol drinking and demonstrate that their disruption lead to increased ethanol sensitivity and withdrawal severity.

Integrative Neurobiology of the Alcohol Withdrawal Syndrome???From Anxiety to Seizures

This article represents the proceedings of a symposium presented at the 2003 Research Society on Alcoholism meeting in Ft. Lauderdale, Florida, organized and chaired by Carl L. Faingold. The presentations were (1) Overview, by Carl L. Faingold; (2) Stress, Multiple Alcohol Withdrawals, and Anxiety, by Darin Knapp; (3) Relationship Between Genetic Differences in Alcohol Drinking and Alcohol Withdrawal, by Julia Chester; (4) Neuronal Mechanisms in the Network for Alcohol Withdrawal Seizures: Modulation by Excitatory Amino Acid Receptors, by Carl L. Faingold; and (5) Treatment of Acute Alcohol Withdrawal and Long-Lasting Alterations in Hippocampal Neuronal Networks, by Larry P. Gonzalez. The presentations emphasized the importance of using intact behaving animals to advance the understanding of the human alcohol withdrawal syndrome. This involves applying and amplifying the neurophysiological and neurotransmitter findings observed in vitro to the network-based neurobiological mechanisms that are involved in several important aspects of the specific behaviors observed clinically. The symposium provided evidence that the organizational aspects of neuronal networks in the intact nervous system add another nexus for the action of alcohol and drugs to treat alcohol withdrawal that may not be readily studied in isolated neural elements used in in vitro approaches.