Blockade of the acquisition of ethanol-induced conditioned place preference by N-methyl-D-aspartate receptor antagonists.

We have examined the influence of two different N-methyl-D-aspartate (NMDA) receptor antagonists on acquisition of the reinforcing properties of ethanol measured in the conditioned place preference (CPP) paradigm in rats. After receiving 15 daily injections of ethanol (0.5 g/kg, i.p.) before the conditioning trials, rats acquired the preference to the compartment paired with ethanol injections during conditioning. Both dizocilpine (0.1 mg/kg, i.p.), a non-competitive antagonist of the NMDA receptor, and L-701,324 (5 mg/kg, per os), an antagonist acting at the strychnine-insensitive glycine site of NMDA receptor complex, when co-administered repeatedly with ethanol, prevented the acquisition of ethanol-induced CPP. Dizocilpine alone provoked the development of CPP, having some intrinsic rewarding properties. In contrast, L-701,324 alone did not affect the CPP. These results suggest that the rewarding properties of ethanol could be, at least in part, due to its action at the NMDA receptor complex. Additionally, we can speculate that NMDA receptor antagonists can be useful in the treatment of ethanol dependence. Glycine receptor antagonists having no abuse potential might have advantages in terms of safety compared to non-competitive NMDA receptor antagonists.     

Positive allosteric modulation of the GABAB receptor by GS39783 attenuates the locomotor stimulant actions of ethanol and potentiates the induction of locomotor sensitization

Acute ethanol-induced locomotor stimulation and ethanol-induced locomotor sensitization are two behavioral assays thought to model the rewarding effects of ethanol. Recent evidence suggests that GS39783, a GABA_B positive allosteric modulator, may be effective at reducing both the rewarding and reinforcing effects of several drugs of abuse, including ethanol. The goal of this study was to determine if GS39783 was capable of altering acute ethanol-induced stimulation, and the induction and expression of ethanol-induced locomotor sensitization, without effecting basal locomotion levels. Several doses of GS39783 (ranging from 0 to 100 mg/kg, depending on experiment) were tested on adult male DBA/2J mice in four experiments using 3-day basal locomotion and acute ethanol stimulation paradigms, and 14-day induction and expression of ethanol sensitization paradigms. The results of experiment 1 are in agreement with current literature, suggesting that 30 mg/kg doses of GS39783 and lower do not alter basal locomotor activity. In experiment 2, we found that GS39783 significantly decreased acute ethanol stimulation, but only at the 30 mg/kg dose, supporting our hypothesis and other publications suggesting that GABA_B receptors modulate acute ethanol stimulation. Contrary to our hypothesis, GS39783 did not alter the expression of locomotor sensitization. Additionally, repeated administration of GS39783 in conjunction with ethanol unexpectedly potentiated ethanol-induced locomotor sensitization. Further study of GS39783 is warranted as it may be a more tolerable treatment for alcoholism than full agonists, due to its behavioral efficacy at doses that lack sedative side effects. Our results add to current literature suggesting that the GABA_B receptor system is indeed involved in the modulation of ethanol-induced locomotor stimulation and sensitization.     

Study on the role of glycine,strychnine-insensitive receptors (glycineB sites) in the discriminative stimulus effects of ethanol in the rat

Several recent studies indicate that both competitive and noncompetitive NMDA receptor antagonists substitute for ethanol in a drug discrimination procedure. In the present study we examined compounds from another class of NMDA receptor antagonists—glycine, strychnine-insensitive, receptor (glycine_B site) antagonists in rats trained to discriminate between IP-administered 1.0 g/kg ethanol (10% v/v) and saline. When the animals met the discriminative criteria, substitution tests were conducted with the noncompetitive NMDA receptor antagonist, memantine (3.0–12.0 mg/kg, IP) and selective, glycine_B site antagonists—L-701,324 (0.3–3.0 mg/kg, IP) and MRZ 2/576 (0.1–10.0 mg/kg, IP). Memantine completely substituted for ethanol at the dose of 6.0 mg/kg, which significantly suppressed the rate of responding. L-701,324 substituted for ethanol at the dose of 3.0 mg/kg, which only tended to decrease the response rate. MRZ 2/576 produced maximal ethanol-appropriate responding (50%) at the dose of 5.0 mg/kg, which did not affect the rate of responding. Glycine (200–800 mg/kg, IP) did not antagonize the ethanol stimulus. These results indicate thatglycine, strychine-insensitive, site antagonists may induce some ethanol-like stimulus effects in the rat.     

Discriminative stimulus effects of ethanol: Lack of antagonism with N-methyl-d-aspartate and d-cycloserine

Several drug discrimination studies reported that both competitive and uncompetitive NMDA receptor antagonist substituted for ethanol stimulus in rats. In the present study we examined if compounds that act as agonists at the NMDA receptor complex, d-cycloserine (a partial agonist at the glycine positive modulatory site) and N-methyl-d-aspartate (an agonist at the glutamate binding site), could antagonize the discriminative stimulus effects of ethanol. Rats were trained to discriminate between IP administered 1.0 g/kg of ethanol (10% v/v) and saline under a sweetened milk-reinforced fixed ratio 10 (FR10) schedule of reinforcement. When the animals met the discriminative criteria, antagonism tests were conducted with d-cycloserine (0.3–10.0 mg/kg, IP) and N-methyl-d-aspartate (15.0–60.0 mg/kg, IP). Neither d-cycloserine nor N-methyl-d-aspartate antagonized the ethanol-mediated discriminative stimulus effects. In addition, d-cycloserine (3.0–300.0 mg/kg, IP) did not substitute for ethanol. These results indicate that at least certain agonists at the NMDA receptor complex do not attenuate the ethanol interoceptive cue in the rat.     

Modulation of ethanol state-dependent learning by dorsal hippocampal NMDA receptors in mice

The possible role of N-methyl-d-aspartate (NMDA) receptors of dorsal hippocampus on ethanol state-dependent learning was studied in adult male mice (Pasteur Institute, Iran). As a model of memory, a single-trial step-down passive avoidance task was used. All animals were bilaterally implanted with cannulae into the CA1 regions of dorsal hippocampi. Results show that intraperitoneal (i.p.) administration of ethanol (0.5 and 1 g/kg) 30 min before training impaired memory performance in animals when tested 24 h later. Pretest administration of the same doses of ethanol-induced state-dependent retrieval of the memory acquired under pretraining ethanol (1 g/kg, i.p.) influence. Pretest intra-CA1 microinjection of NMDA (0.001, 0.01, and 0.1 μg/mouse) by itself had no effect on memory retrieval and ethanol-induced amnesia. However, pretest intra-CA1 administration of the same doses of NMDA with an ineffective dose of ethanol (0.25 g/kg, i.p.) significantly restored the retrieval and potentiated ethanol state-dependent learning. On the other hand, pretest administration of a competitive NMDA receptor antagonist d-AP5 (d-(−)-2-Amino-5-phosphonopentanoic acid) (0.01, 0.1, and 1 μg/mouse, intra-CA1) or a noncompetitive NMDA receptor antagonist MK-801 maleate [(5S, 10R)-(+)-5-Methyl-10, 11-dihydro-5H-dibenzo [a, d] cyclohepten-5, 10-imine maleate] (0.25, 0.5, and 1 g/mouse, intra-CA1) 5 min before the administration of ethanol (1 g/kg, i.p.) significantly inhibited ethanol state-dependent learning. Intra-CA1 pretest administration of d-AP5 (0.01, 0.1, and 1 μg/mouse) or MK-801 maleate [5S, 10R)-(+)-5-Methyl-10, 11-dihydro-5H-dibenzo [a, d] cyclohepten-5, 10-imine maleate] (0.25, 0.5, and 1 μg/mouse) alone did not affect memory retention. It may be concluded that dorsal hippocampal NMDA receptors are involved in mediating ethanol state-dependent learning.     

Motor impairment produced by ethanol and site-selective NMDA receptor antagonists in mice: tolerance and cross-tolerance.

Current perspectives on clinical use of N-methyl-D-aspartate (NMDA) receptor antagonists infer acute and repeated administration schedules for management of different pathological states. Development of tolerance and cross-tolerance between different antagonists may significantly affect their clinical effectiveness. Since ethanol was repeatedly demonstrated to act as NMDA receptor antagonist, ethanol use may also have its impact on the effects of NMDA receptor ligands. Using the rotarod test in mice, the present study evaluated development of tolerance and cross-tolerance between ethanol (3.2 g/kg, p.o.), competitive NMDA receptor antagonist, D-CPPene (5.6 mg/kg, i.p.), and low-affinity NMDA receptor channel blocker, memantine (30 mg/kg, i.p.), that were administered for seven days once a day after the daily rotarod training session. Acute tests with ethanol (0.3, 1, 1.7, 3.2 g/kg), D-CPPene (0.3, 1, 3, 5.6 mg/kg) and memantine (1, 3, 10, 30 mg/kg) revealed that (a) each of these drugs dose-dependently disrupted rotarod performance in drug-naive mice; (b) in ethanol- and D-CPPene-treated mice, tolerance was observed to ethanol and D-CPPene but not to memantine; moreover, effects of memantine were even more pronounced in D-CPPene-treated subjects; and (c) repeated memantine administration decreased acute motor impairing effects of ethanol, D-CPPene and memantine. Thus, the history of ethanol use or abuse may influence pharmacological activity of NMDA receptor antagonists and this effect is dependent on type of the NMDA receptor antagonist applied.     

Chronic tolerance to ethanol-induced sedation: Implication for age-related differences in locomotor sensitization

The adolescent brain has been suggested to be particularly sensitive to ethanol-induced neuroadaptations, which in turn could increase the risk of youths for alcohol abuse and dependence. Sensitization to the locomotor stimulant effects of ethanol has often been used as an animal model of ethanol-induced neuroadaptations. Previously, we showed that young mice were more sensitive than adults to the locomotor sensitization induced by high ethanol doses. However, this effect could be due to age-related differences in chronic tolerance to the sedative effects of ethanol. The aim of the present study is to assess chronic tolerance to the sedative effects of ethanol in weaning 21-day-old (P21), adolescent 35-day-old (P35) and adult 63-day-old (P63) female Swiss mice. After a daily injection of saline or 4 g/kg ethanol during 6 consecutive days, all P21, P35 and P63 mice were injected with 4 g/kg ethanol and submitted to the loss of righting reflex procedure. Our results confirm that the sensitivity to the acute sedative effects of ethanol gradually increases with age. Although this schedule of ethanol injections induces significant age-related differences in ethanol sensitization, it did not reveal significant differences between P21, P35 and P63 mice in the development of a chronic ethanol tolerance to its sedative effects. The present results show that age-related differences in the development of ethanol sensitization cannot be explained by differences in chronic ethanol tolerance to its sedative effects. More broadly, they do not support the idea that ethanol-induced sensitization is a by-product of chronic ethanol tolerance.     

Effects of N-methyl-D-aspartate receptor antagonists on reinforced and nonreinforced responding for ethanol in rats.

Results of several recent studies indicate that the discriminative stimulus effects of ethanol are related, at least partially, to ethanol-induced decrease in the N-Methyl-D-aspartate (NMDA) receptor function. The role of NMDA receptors in ethanol reinforcement remains still unclear. The aim of the present study was to evaluate the effects of two novel NMDA receptor antagonists in rats lever pressing for 8% ethanol in the oral self-administration procedure. In addition, the effects of the drugs on intensity of nonreinforced responding for ethanol (i.e., "experimental craving") were examined in the extinction procedure. To assess selectivity of the drugs' actions the same range of doses was tested in rats lever pressing for water (control experiments). A low-affinity, uncompetitive NMDA receptor antagonist, MRZ 2/579 (2.5-7.5 mg/kg) selectively and dose-dependently decreased ethanol self-administration. This compound exerted also selective effects on nonreinforced responding for ethanol with lower dose (2.5 mg/kg) increasing and higher dose (5 mg/kg) suppressing operant behavior in the extinction procedure. MRZ 2/579 (5 mg/kg) did not alter open field activity when given in combination with either saline or ethanol (0.5-1 g/kg). In contrast, a glycineB site antagonist, MRZ 2/576 (2.5-7.5 mg/kg) did not produce any selective effects on either reinforced or nonreinforced lever pressing for ethanol. The present results suggest that MRZ 2/579 may selectively suppress both ethanol self-administration and experimental ethanol craving.     

The neuropeptide-Y Y5 receptor antagonist L-152,804 decreases alcohol self-administration in inbred alcohol-preferring (iP) rats.

Neuropeptide-Y (NPY) is the most abundant and widely distributed peptide in the mammalian central nervous system and increases feeding behavior through actions at the Y5 receptor subtype. Recent pharmacological evidence indicates that NPY activity at this receptor subtype can modulate ethanol reinforcement. The purpose of this study was to determine if NPY Y5 receptor antagonism reduces ethanol self-administration and reinforcement in a rodent genetic animal model of alcoholism. Selectively inbred alcohol-preferring (iP) rats were trained to voluntarily consume ethanol (10% vol/vol) versus H2O in a 24-h two-bottle choice test. An additional group of iP rats was trained in operant ethanol self-administration to lever press on a fixed-ratio 1 schedule for ethanol (10% vol/vol) reinforcement. Following establishment of baseline intake or ethanol-reinforced responding, iP rats were injected with L-152,804 (0-20 mg/kg) prior to two-bottle or operant ethanol self-administration sessions. In the two-bottle choice test, L-152,804 (3 and 10 mg/kg, ip) significantly reduced ethanol intake (g/kg) at 4- and 6-h postinjection and had no effect on food intake. In the operant procedure, L-152,804 (10 and 20 mg/kg, ip) significantly reduced both the dosage of self-administered ethanol (g/kg/1-h) and the total number of ethanol-reinforced responses. No effect was observed on latency to the first response or the number of inactive lever presses. These results indicate that blockade of NPY Y5 receptor activity decreases both voluntary ethanol drinking and ethanol reinforcement in a rodent genetic animal model of alcoholism. For this reason, NPY Y5 receptor antagonists may be useful in medical management of alcohol abuse and alcoholism in the human population.     

Chronic ethanol up-regulates the synaptic expression of the nuclear translational regulatory protein AIDA-1 in primary hippocampal neurons

Recent studies have identified synaptic proteins that undergo synapse-to-nucleus translocation in response to neuronal activity that modulate protein synthesis. One such translational regulatory protein of the postsynaptic density (PSD) is AIDA-1d, which binds to PSD-95 via its C-terminus. Activation of synaptic NMDA receptors induces the cleavage of AIDA-1d, and the N-terminus is then shuttled to nuclear Cajal bodies where it plays a role in regulating global protein synthesis. Chronic ethanol exposure has been shown to increase the synaptic clustering of NMDA receptors and PSD-95. Here, we tested the hypothesis that AIDA-1d regulates chronic ethanol-induced increases in synaptic NMDA receptor expression. As reported, we found that AIDA-1 was highly enriched in dendritic spines and co-localized with PSD-95. Acute NMDA treatment increased AIDA-1 colocalization with p80 coilin, a marker of Cajal bodies. Chronic treatment (4 day) of cultures with ethanol (25–100 mM) or with the NMDA receptor antagonist AP-V (50 μM) enhanced the clustering of AIDA-1 at synaptic sites. However, chronic ethanol treatment (50 mM) in the presence of the NMDA receptor agonist NMDA (2.5 μM) prevented this increase. Surprisingly, PSD-95 did not seem to play a role in the synaptic distribution of AIDA-1 as this distribution was not affected by declustering PSD-95 from synapses in response to inhibition of palmitoylation. We found that lentiviral knockdown of AIDA-1d did not affect protein expression levels of NMDA receptor subunits GluN1, GluN1 C2′, or GluN2B. The results of this study demonstrate that synaptic AIDA-1 expression is enhanced by chronic ethanol exposure that can be prevented by concurrent stimulation of NMDA receptors. In addition, we found that the association of AIDA-1 with PSD-95 is not required for its localization to the PSD. Moreover, we found that AIDA-1 does not regulate protein expression levels or alternative splicing of the GluN1 subunit of NMDA receptors.     

Antagonists and agonists at the glycine site of the NMDA receptor for therapeutic interventions

For decades neuroreceptor research has focused on the development of NMDA glycine-site antagonists, after Johnson and Ascher found out in 1987 about the co-agonistic character of this achiral amino acid at the NMDA receptor. Contrary to the inhibitory glycine receptor (glycine(A)) the glycine binding site on the NMDA receptor (glycine(B)) is strychnine-insensitive. A great diversity of diseases showing a disturbed glutamate neurotransmission have been linked to the NMDA receptor. Glycine site antagonists have been investigated for acute diseases like stroke and head trauma as well as chronic ones like dementia and chronic pain.     

Alterations of motor performance and brain cortex mitochondrial function during ethanol hangover

Ethanol has been known to affect various behavioral parameters in experimental animals, even several hours after ethanol (EtOH) is absent from blood circulation, in the period known as hangover. The aim of this study was to assess the effects of acute ethanol hangover on motor performance in association with the brain cortex energetic metabolism. Evaluation of motor performance and brain cortex mitochondrial function during alcohol hangover was performed in mice 6 hours after a high ethanol dose (hangover onset). Animals were injected i.p. either with saline (control group) or with ethanol (3.8 g/kg BW) (hangover group). Ethanol hangover group showed a bad motor performance compared with control animals (p < .05). Oxygen uptake in brain cortex mitochondria from hangover animals showed a 34% decrease in the respiratory control rate as compared with the control group. Mitochondrial complex activities were decreased being the complex I–III the less affected by the hangover condition; complex II–III was markedly decreased by ethanol hangover showing 50% less activity than controls. Complex IV was 42% decreased as compared with control animals. Hydrogen peroxide production was 51% increased in brain cortex mitochondria from the hangover group, as compared with the control animals. Quantification of the mitochondrial transmembrane potential indicated that ethanol injected animals presented 17% less ability to maintain the polarized condition as compared with controls. These results indicate that a clear decrease in proton motive force occurs in brain cortex mitochondria during hangover conditions. We can conclude that a decreased motor performance observed in the hangover group of animals could be associated with brain cortex mitochondrial dysfunction and the resulting impairment of its energetic metabolism.     

The effect ofin vitro andin vivo ethylenbis dithiocarbamate fungicides on NMDA receptors in rat brain membranes

To determine whether the ethlenbisdithiocarbamate fungicides, zineb, manzeb and maneb affect the N-methyl-D-aspartate (NMDA) receptor in rat brain membranes, we performed a binding assay using [³H]MK-801, a noncompetitive NMDA receptor antagonist. Displacement studies were conducted using well washed membranes to exclude the effect of endogenous acidic amino acids on the binding of [³H]MK-801. In both the presence or absence of added glutamate and glycine in the assay buffer, the dose-response curve indicated that zineb enhanced the binding in a concentration range of 100–500 μM. However, the displacement curves indicated that manzeb and maneb inhibited the binding in a concentration range of 10–500 μM. The addition of 50 μM glutamate and glycine to the assay medium increased binding by 5–20% above the control in a concentration range of 0.1–100 μM. No rats injected with zineb, manzeb, maneb (100 mg/kg, ip) showed any characteristic toxic signs or any significant weight changes within 24 hrs. Estimation of [³H]MK-801 binding to unwashed membranes from intoxicated rat brains revealed no marked change in Bmax or Kd values for 24 hrs following fungicide administration.     

Ethanol intake and ethanol-conditioned place preference are reduced in mice treated with the bioflavonoid agent naringin

Recently, PPAR-γ activation has emerged as a potential treatment for alcoholism. However, the adverse effects of synthetic PPAR-γ activators, despite being effective drugs, prompted the need for novel PPAR-γ agonists that retain efficacy and potency with a lower potential of side effects. Hence, naringin, a bioflavonoid isolated from citrus fruits and recently identified as a natural ligand of PPAR-γ, has begun to be evaluated for treatment of alcoholism. It is well known to possess several therapeutic benefits in addition to its anti-anxiety and antidepressant properties. In the present study, we assessed whether naringin treatment possesses anti-ethanol reward properties in C57BL/6 mice. We used the two-bottle choice drinking paradigm and ethanol-induced conditioned place preference (CPP) to examine the effect of naringin treatment on ethanol drinking. Results have shown that, compared with vehicle, naringin (10–100 mg/kg) significantly and dose-dependently decreased voluntary ethanol intake and preference in a two-bottle choice drinking paradigm [3–15% (v/v) escalating over 2 weeks], with no significant effect observed on saccharin [0.02–0.08% (w/v)] or on quinine [15–60 μM (w/v)] intake. In addition, there was no significant difference in blood ethanol concentration (BEC) between groups following naringin administration of 3 g of ethanol/kg body weight. Interestingly, when mice were treated with vehicle or naringin (30 mg/kg) before injection of ethanol (1.5 g/kg) during conditioning days, naringin inhibited the acquisition of ethanol-CPP. More importantly, these effects were significantly attenuated when mice were pre-injected with the peroxisome proliferator-activated receptor-γ (PPAR-γ) antagonist, GW9662. Taken together, the present findings are the first to implicate naringin and PPAR-γ receptors in the behavioral and reward-related effects of ethanol and raise the question of whether specific drugs that target PPAR-γ receptors could potentially reduce excessive ethanol consumption and preference.     

Effects of GABA antagonists and habituation to novelty on ethanol-induced locomotor activity in mice.

The effects of the gamma-aminobutyric acid (GABA) antagonists picrotoxin and bicuculline on ethanol-induced motor excitation were assessed on habituated and non-habituated mice. Habituated mice were exposed to the testing apparatus for 30 min on 4 consecutive days before testing. Mice were treated with several doses of ethanol (0.8, 1.2 and 1.6 g/kg, intraperitoneally) and at each dose were pretreated with picrotoxin (0.25, 0.5 and 1.0 mg/kg, i.p.) or bicuculline (0.5, 1.0 and 2.0 mg/kg, i.p.). Habituated animals had consistently lower scores than non-habituated animals throughout the experiment. Ethanol alone produced a significant increase in motor activity. Picrotoxin and bicuculline alone decreased motor activity only at the two higher doses in both habituated and non-habituated mice. For the non-habituated mice, picrotoxin and bicuculline at the lowest doses decreased ethanol induced motor activity at the 0.8 and 1.2 g/kg ethanol doses, whereas in habituated mice, only bicuculline attenuated activity. At the highest dose of ethanol, picrotoxin increased ethanol-induced excitation for both non-habituated and habituated animals, whereas bicuculline only augmented the activity of the non-habituated animals at this ethanol dose. Neither antagonist affected blood-ethanol levels. These results suggest that habituation affects not only motor activity per se but also changes in activity due to the combination of GABA antagonists and ethanol.     

Chronic intermittent exposure to ethanol during adolescence produces tolerance to the hypnotic effects of ethanol in male rats: a dose-dependent analysis

Adolescence is a time period when distinct behavioral and neurophysiological changes occur. Novelty seeking is common during this developmental period, and binge alcohol consumption by adolescents is prevalent. Adolescents, as compared to adults, have been shown to display decreased sensitivity to many effects of ethanol, including effects that may serve as cues to moderate consumption. Consequently, reduction of these factors could facilitate drinking behaviors in adolescents, which may disrupt normal developmental processes. Chronic intermittent ethanol exposure (CIEE) to high doses of ethanol in rats has been shown to prevent normal developmental increases in sensitivity to ethanol-induced loss of righting reflex (LORR). However, it is unknown whether the same disruptions would occur following CIEE to more moderate and low alcohol doses. The present study was designed to evaluate the effects of CIEE in rats to several different doses during adolescence on ethanol-induced LORR in adulthood. Male rats were weighed and treated intraperitoneal with 1.0, 2.0, 3.0, or 4.0 g/kg ethanol or equivolume saline (equivalent to 4.0 g/kg dosings) every 48 hours for 20 days beginning on postnatal day (PN) 30. LORR was measured following each ethanol exposure. Finally, LORR was measured in both ethanol and saline-exposed animals following 4.0 g/kg ethanol challenge on PN 50 and following a 12-day withdrawal period (PN62). Duration of LORR remained unchanged throughout the adolescent exposure period. However, when LORR was measured on PN50 and PN62, 4.0 and 3.0 g/kg treatment groups displayed significantly less LORR compared to the free feeding and 1.0 g/kg ethanol treated groups. Animals displayed no tolerance development to LORR throughout the chronic exposure period even though moderate and high doses of ethanol were used. CIEE to high (3.0 or 4.0 g/kg) doses of ethanol disrupted the expected developmental increase in sensitivity to ethanol-induced LORR. These results may have implications for human adolescent drinkers. Specifically due to adolescents' relative resistance to the hypnotic effects of alcohol and their tendency to intake alcohol in an intermittent, or binge-like, manner such tolerance might lead to increases in alcohol abuse in this population of drinkers.     

Protective effects of zinc sulfate and L-lysine on acute ethanol toxicity in mice

Survival rates were determined in three groups of male CF-1 mice, treated ip with single and multiple doses of zinc sulfate and/or l-lysine, each alone and in combination, followed by administration of an acute toxic dose of ethanol 1 hr post-treatment. Significant protective effects were observed in all pretreated groups. Zinc and lysine (combined)-treated groups showed a maximal protective effect. Blood ethanol determinations were also made in mice similarly pretreated with zinc sulfate (5 μg/kg) and/or l-lysine (2.5 g/kg) ip and subjected to 4.55 g/kg ethanol ip 1 hr post-treatment. Blood ethanol values were significantly lower in the lysine-treated group (P < 0.05) at 0.5 hr and the zinc-lysine group (P < 0.001) at 1 hr. The zinc-treated group showed a steeper ethanol disappearance curve beyond 2 hr. Histological evaluations of livers from treated and ethanol control animals showed no pathological changes in any group.     

Place conditioning with ethanol in rats bred for high (UChB) and low (UChA) voluntary alcohol drinking

The main goal of this study was to investigate the ability of an ethanol dose (1 g/kg) administered intraperitoneally to induce conditioned place preference (CPP) and/or conditioned place aversion (CPA) in two lines of rats selectively bred for their high (UChB) or low (UChA) voluntary ethanol intake. It was found that five pairings with ethanol induced CPA in ethanol-naïve rats of both lines, but the magnitude of avoidance was lower in the UChB relative to the UChA rats, indicating that ethanol was less aversive to naïve rats bred for high alcohol drinking. After 2 months of high voluntary ethanol drinking (∼6–7 g/kg/day), in free choice between 10% ethanol and water, ethanol produced CPP in UChB rats, reflecting that ethanol had become rewarding to these rats. By contrast, the low voluntary ethanol intake (<1 g/kg/day) displayed by UChA rats preexposed for 2 months in free choice did not change ethanol-induced CPA. However, preexposure of UChA rats to forced ethanol drinking (∼5.7 g/kg/day) and the later inhibition of ethanol-derived acetaldehyde by 4-methylpyrazole (10 mg/kg intraperitoneal), an inhibitor of the enzyme alcohol dehydrogenase, not only increased their voluntary ethanol intake in free choice, but also had a facilitating effect on the development of CPP. Taken together, these results show that the expression of the reinforcing effects of ethanol required a period of voluntary ethanol intake in UChB rats, whereas in UChA rats, both prior exposure to forced ethanol drinking and reduction of high blood ethanol-derived acetaldehyde were required.     

Ethanol-induced hyperactivity is associated with hypodopaminergia in the 22-TNJ ENU-mutated mouse

Characterization of neurochemical and behavioral responses to ethanol in phenotypically distinct mouse strains can provide insight into the mechanisms of ethanol stimulant actions. Increases in striatal dopamine (DA) levels have often been linked to ethanol-induced hyperactivity. We examined the functional status of the DA system and behavioral responsiveness to ethanol, cocaine, and a DA-receptor agonist in an N-ethyl-N-nitrosourea-mutagenized mouse strain, 22-TNJ, generated by the Integrative Neuroscience Initiative on Alcoholism Consortium. The 22-TNJ mouse strain exhibited greater locomotor responses to 2.25 g/kg ethanol and 10 mg/kg cocaine, compared with control mice. In vivo microdialysis showed low-baseline DA levels and a larger DA increase with both 2.25 g/kg ethanol and 10 mg/kg cocaine. In in vitro voltammetry studies, the 22-TNJ mice displayed increased V_max rates for DA uptake, possibly contributing to the low-baseline DA levels found with microdialysis. Finally, 22-TNJ mice showed enhanced in vitro autoreceptor sensitivity to the D2/D3 agonist, quinpirole, and greater locomotor responses to both autoreceptor-selective and postsynaptic receptor-selective doses of apomorphine compared with controls. Taken together, these results indicate that the dopaminergic system of the 22-TNJ mouse is low functioning compared with control, with consequent receptor supersensitivity, such that mutant animals exhibit enhanced behavioral responses to DA-activating drugs, such as ethanol. Thus, the 22-TNJ mouse represents a model for a relatively hypodopaminergic system, and could provide important insights into the mechanisms of hyper-responsiveness to ethanol's stimulant actions.