dizocilpine-maleate and Alcoholism

Effects of acamprosate and ionotropic uncompetitive N-methyl-D-aspartate receptor antagonists and group I metabotropic glutamatergic receptor antagonists on the expression of ethanol-induced sensitization were investigated in mice. The results indicated that acamprosate (200 and 400 mg/kg) and N-methyl-D-aspartate receptor antagonists, neramexane (10 and 20 mg/kg) and MK-801 (0.1 and 0.2 mg/kg), inhibited the expression of ethanol-induced sensitization. Acamprosate, but not the other compounds tested, also blocked the stimulant effect of acute injections of ethanol. Among the group I metabotropic glutamatergic receptor antagonists, only the metabotropic glutamatergic receptor 5 antagonist, MTEP (5, 10, and 20 mg/kg) showed an effect similar to the N-methyl-D-aspartate receptor antagonists. The metabotropic glutamatergic receptor 1 antagonist, EMQMCM (5, 10, and 20 mg/kg), however, potentiated the inhibitory effect of MK-801 on the expression of ethanol-induced sensitization. The findings indicate that glutamatergic neurotransmission is important in the ethanol-induced sensitization process, and suggest that co-administration of metabotropic glutamatergic receptor 1 antagonists and N-methyl-D-aspartate receptor antagonists may be useful in therapy for alcoholism.

Topics: Acamprosate; Alcoholism; Animals; Brain; Cyclopentanes; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Synergism; Ethanol; Glutamic Acid; Male; Mice; Motor Activity; N-Methylaspartate; Pyridines; Quinolines; Receptors, Metabotropic Glutamate; Receptors, N-Methyl-D-Aspartate; Stereotyped Behavior; Synaptic Transmission; Taurine; Thiazoles

Chronic alcohol misuse by human subjects leads to neuronal loss in regions such as the superior frontal cortex (SFC). Propensity to alcoholism is associated with several genes. gamma-Aminobutyric acid (GABA)(A) receptor expression differs between alcoholics and controls, whereas glutamate receptor differences are muted. We determined whether genotype differentiated the regional presentation of GABA(A) and glutamate-NMDA (N-methyl-d-aspartate) receptors in SFC. Autopsy tissue was obtained from alcoholics without comorbid disease, alcoholics with liver cirrhosis, and matched controls. ADH1C, DRD2B, EAAT2, and APOE genotypes modulated GABA(A)-beta subunit protein expression in SFC toward a less-effective form of the receptor. Most genotypes did not divide alcoholics and controls on glutamate-NMDA receptor pharmacology, although gender and cirrhosis did. Genotype may affect amino acid transmission locally to influence neuronal vulnerability.

Topics: Alcoholism; Brain; Case-Control Studies; Cerebral Cortex; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Gene Expression; Humans; Liver Cirrhosis, Alcoholic; Protein Isoforms; Receptors, GABA-A; Receptors, N-Methyl-D-Aspartate

Millions of Americans suffer from Alzheimer's Disease (AD), which is characterized by significant neurological impairment and an accumulation in brain tissue of senile plaques consisting of beta amyloid (Abeta) peptide. The hippocampus, a region primarily responsible for learning and memory, appears to be particularly susceptible to AD-related injury and chronic alcohol abuse. Although certain risk factors for AD are known, it is unclear if alcohol abuse or dependence may contribute to neuropathology in AD. Recent research suggests that low-to-moderate consumption of alcohol may protect against development of AD, while alcohol dependence may increase risk of developing AD. Therefore, the current studies aimed to investigate the effects of exposure to 50 or 100 mM ethanol (EtOH) and withdrawal on hippocampal injury induced by Abeta peptide treatment.. The present studies exposed organotypic hippocampal slice cultures to 50 or 100 mM ethanol (EtOH) for 10 days, after which the slices underwent ethanol withdrawal (EWD) in the presence of varying concentrations of Abeta 25-35 (0.1, 1, 10 microM), or 35-25 (200 microM), a negative control reverse sequence peptide. Cellular injury, as evidenced by uptake of propidium iodide (PI), was assessed for each subregion of the hippocampal complex (CA1, CA3, and dentate gyrus).. Cellular injury in the CA1 pyramidal cell layer was significantly increased during withdrawal from exposure to 100 mM, but not 50 mM, EtOH. Exposure to Abeta in ethanol-naïve cultures did not produce significant cytotoxicity. However, exposure to Abeta during EWD from 100 mM produced marked increases in CA1 pyramidal cell region cytotoxicity, effects reversed by cotreatment with a nontoxic concentration of the NMDA receptor channel blocker MK-801 (20 microM).. These data suggest that withdrawal from exposure to a high concentration of EtOH produces marked cellular injury in the hippocampus, particularly the CA1 subregion. Further, this EtOH exposure and withdrawal regimen sensitizes the hippocampus to the toxic effects of Abeta treatment in a manner reflecting over activity of NMDA receptor function.

Topics: Alcohol Drinking; Alcoholism; Alzheimer Disease; Amyloid beta-Peptides; Animals; Dizocilpine Maleate; Dose-Response Relationship, Drug; Ethanol; Hippocampus; Propidium; Pyramidal Cells; Rats; Receptors, N-Methyl-D-Aspartate; Tissue Culture Techniques

The ability of drugs that reduce NMDA receptor activity on the volitional consumption of ethanol in the genetic drinking rat, mHEP line, was investigated. After the consumption of ethanol solutions and water by each male or female mHEP rat had stabilized on its preferred concentration, different doses of LY 274614, a competitive NMDA antagonist, MK 801, a non-competitive NMDA antagonist, (+)-HA-966 or ACPC (1-aminocyclopropane-1-carboxylic acid), antagonists of the glycine site were administered daily for three days. The dose of 3.0 mg/kg i.p. LY 274614 reduced the consumption of ethanol by 64% compared to the pre-treatment baseline, while 0.3 mg/kg of MK 801 reduced consumption by 44%, 20 mg/kg (+)-HA-966 reduced consumption by 47% and 300 mg/kg of ACPC reduced consumption by 30%. These doses of LY 274614 and MK 801 reduced the ability of Sprague-Dawley rats to walk on a rotorod. Effects of these drugs on food intake were small except for the 20 mg/kg dose of (+)-HA-966. Therefore, the drugs did not have an anti-caloric effect and manipulations of the glutamatergic system through NMDA receptors may modify the consumption of ethanol. This interaction should be explored further for its therapeutic potential and to better understand the control by central neuronal systems of the consumption of ethanol.

Topics: Alcohol Drinking; Alcohol-Induced Disorders, Nervous System; Alcoholism; Amino Acids, Cyclic; Animals; Brain; Disease Models, Animal; Dizocilpine Maleate; Dose-Response Relationship, Drug; Ethanol; Excitatory Amino Acid Antagonists; Female; Genetic Predisposition to Disease; Glutamic Acid; Isoquinolines; Male; Motor Activity; Pyrrolidinones; Rats; Rats, Inbred Strains; Rats, Sprague-Dawley; Receptors, Glycine; Receptors, N-Methyl-D-Aspartate; Synaptic Transmission; Volition

This study tests the hypothesis that glutamate receptors are altered in the brains of alcoholics as a result of chronic alcohol neurotoxicity. Excessive release of the excitatory neurotransmitter glutamate may damage postsynaptic neurons by increasing calcium flux through N-methyl-D-aspartate (NMDA) receptor-gated ion channels. Alcohol has opposite effects on the NMDA receptor, depending on the duration of exposure. Acute exposure to alcohol inhibits ion flow through NMDA receptors, whereas chronic exposure upregulates the number of these receptors and thereby increases ion flow. Acute withdrawal from alcohol results in hyperexcitability and seizures in the presence of upregulated NMDA receptors, making postsynaptic neurons vulnerable to excitotoxic damage. For this study, 13 grossly and histologically normal brains from alcoholics and 13 brains from nonalcoholic controls were selected from our brain bank. The two groups were matched for age, postmortem interval, and storage time. Maximal binding and affinities of NMDA receptors were determined by quantitative autoradiography in the cingulate cortex, the cornu Ammonis of the hippocampus, and in the cerebellar vermis. Binding was determined with an agonist, L-[3H]glutamate, with a competitive antagonist, [3H]CGP-39653, and with an antagonist binding in the channel interior, [3H]MK-801. No significant differences were found in receptor densities or affinities between alcoholics and controls. Real differences were not likely to be obscured by nonalcohol-related variables because the groups were closely matched for age, autopsy delay, time in storage, and central nervous system medications. Various diseases causing acute and chronic hypoxia did not significantly affect receptor density or affinity. Liver diseases and thiamine deficiency were excluded. A long-lasting upregulation of the number or affinity of NMDA receptors is not a key feature of chronic alcoholics.

Topics: 2-Amino-5-phosphonovalerate; Aged; Alcoholism; Cerebellar Cortex; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Glutamic Acid; Gyrus Cinguli; Hippocampus; Humans; Middle Aged; Receptors, Glutamate

Effects of prenatal ethanol exposure on extracellular glutamate accumulation stimulated by glutamate receptor agonists were studied in rat cerebellar granule cell cultures. The prenatal exposure to ethanol was achieved via maternal consumption of a Sustacal liquid diet containing either 5% ethanol or isocaloric sucrose (pair-fed) substituted for ethanol from gestation d 11 until the day of parturition. Neither the basal level of extracellular glutamate nor the increased accumulation of glutamate stimulated by KCl (40 mM) or by ionotropic glutamate receptor agonists, N-methyl-D-aspartate (NMDA) or kainate (KA) (100 microM each), in cells prepared from the ethanol-fed group was significantly different from that in cells prepared from the pair-fed group. Glutamate accumulation stimulated by quisqualate (QA, 100 microM) or by trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD, 250 microM) in the ethanol-fed group was higher than that in the pair-fed group by 116 and 36%, respectively. In the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, 100 microM), an ionotropic QA receptor antagonist, the QA-induced accumulation of glutamate in the ethanol-fed group was still higher than that in the pair-fed group. In the presence of MK-801 (5 microM), an antagonist of the NMDA receptor, the enhanced accumulation of glutamate stimulated by either QA or t-ACPD was still observable in the ethanol-fed group as compared to the pair-fed group. Addition of (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG, 500 microM), a selective antagonist of the metabotropic glutamate receptor, abolished the enhanced accumulation of glutamate stimulated by either QA or t-ACPD in the ethanol-fed group. Although immunoblotting of mGluR1 and mGluR2/3 did not show apparent differences between the pair-fed and the ethanol-fed groups, the overall results suggest that the effect of prenatal ethanol exposure was selectively through a pathway mediated by the metabotropic glutamate receptor.

Topics: Alcoholism; Amino Acids; Animals; Cells, Cultured; Cerebellum; Cycloleucine; Dizocilpine Maleate; Ethanol; Female; Glutamic Acid; Kainic Acid; N-Methylaspartate; Neurons; Potassium Chloride; Pregnancy; Pregnancy Complications; Prenatal Exposure Delayed Effects; Quisqualic Acid; Rats; Rats, Sprague-Dawley; Receptors, Metabotropic Glutamate

Acamprosate is a putative anticraving drug used to maintain abstinence in alcohol-dependent patients. Its mechanism of action is uncertain, but the drug is thought to interact with neuronal NMDA receptors and calcium channels, and these proteins are implicated in the induction of alcohol dependence. In these experiments, the effects of acamprosate were studied on the binding of the NMDA receptor ligand [3H]dizocilpine to rat brain membranes under nonequilibrium conditions; 10 microM glutamate and 1 microM glycine were present in the binding assays to partially activate the receptor. At clinically relevant concentrations (in the micromolar range), acamprosate significantly enhanced [3H]dizocilpine binding to cortical membranes from control animals (suggesting that acamprosate may increase the rate of association of the radioligand), whereas at higher concentrations binding was inhibited. This effect is consistent with a partial agonist effect of acamprosate on the NMDA receptor protein. However, when rats were made dependent on ethanol (exposure to the drug for 10 days by inhalation) and cortical membranes were prepared from these animals, acamprosate in vitro no longer produced any enhancement of [3H]dizocilpine binding. Similar results were obtained when membranes were used from rats that had received 400 mg/kg/day of acamprosate in their drinking water with or without concurrent ethanol inhalation for 10 days. Thus, in brain membranes from all these treatment groups, acamprosate in vitro caused inhibition of [3H]dizocilpine binding only. The results suggest that acamprosate may have excitatory or inhibitory effects on NMDA receptors, depending on the experimental conditions. The effects of the drug on this system appear to be shifted toward inhibition in alcohol dependence, and this finding may be important to its clinical mechanism.

Topics: Acamprosate; Alcohol Deterrents; Alcoholism; Animals; Cerebral Cortex; Culture Techniques; Dizocilpine Maleate; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists; Male; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Taurine

The role of the N-methyl-D-aspartate (NMDA) receptors in differential ethanol sensitivity of the alcohol-insensitive [alcohol-tolerant (AT)] and alcohol-sensitive [alcohol-nontolerant (ANT)] rat lines selected for low and high sensitivity to ethanol-induced (2 g/kg) motor impairment was studied in behavioral and neurochemical experiments. A noncompetitive antagonist of the NMDA receptor, dizocilpine maleate (MK-801; 0.2 mg/kg), impaired motor function in ANT rats, but not in AT rats, in a tilting plane test. The impairment was further potentiated by a dose (0.75 g/kg) of ethanol, which alone was inactive. This effect was apparently not associated with the locomotor stimulation produced by MK-801 (0.1 and 0.2 mg/kg), because stimulation did not differ between the rat lines. Locomotor stimulation was potentiated by the low ethanol dose in both rat lines. Ethanol treatment decreased the cerebellar and hippocampal cGMP concentrations both with and without MK-801 pretreatment in both rat lines. In situ hybridization using oligonucleotide probes specific for NMDA receptor subunit mRNAs NR1 and NR2A, B, C, and D revealed no clear differences in brain regional expression between ANT and AT rates. These results indicate that the alcohol-sensitive ANT rats are very sensitive to a low dose of ethanol in the presence of NMDA receptor antagonism, consistent with the hypothesis that this receptor system is involved in acute ethanol intoxication.

Topics: Alcoholism; Animals; Cerebellum; Cyclic GMP; Dizocilpine Maleate; Ethanol; Gene Expression; Hippocampus; Male; Motor Activity; Motor Skills; Postural Balance; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; RNA, Messenger

The amino acid L-glutamate is a major excitatory neurotransmitter that is involved in many CNS functions, including learning, memory, long-term potentiation, and synaptic plasticity. Acute exposures to ethanol (50 to 200 mM) have been shown to inhibit NMDA receptor responses, whereas chronic exposure to ethanol leads to adaptive supersensitivity thought to be involved in ethanol dependence and tolerance. To investigate the effects of chronic ethanol exposure on glutamate receptor density, we examined the binding of both NMDA and non-NMDA ligands in rat brain after several chronic ethanol treatment protocols using a number of different rat strains. No increases in the binding of [3H]MK-801, [3H]CGP 39653, or the polyamine specific competitive antagonist, [3H]ifenprodil, were seen after two well-used chronic ethanol treatments. These included the 2-week liquid diet developed by Frye et al. (J. Pharmacol. Exp. Ther. 216:306-314, 1981) and the 4-day binge treatment developed by Majchrowicz (Psychopharmacologia 43:245-254, 1975). However, small increases in the binding of both the NMDA noncompetitive antagonist [3H]MK-801, as well as the competitive NMDA antagonist [3H]CGP 39653, were seen in select frontal brain regions after 3 weeks of the Walker-Freund chronic ethanol liquid diet. When this chronic liquid diet treatment was extended to a period of 6 weeks, these increases in receptor binding were diminished to nonsignificant levels. The binding of the non-NMDA ligands [3H]AMPA and [3H]kainate were not significantly affected by either length of Walker-Freund liquid diet exposure. When rats were treated chronically with ethanol for 30 days using the paradigm developed by Tsukamoto et al. (Hepatology 5:224-232, 1985), small, but significant, increases in the binding of [3H]MK-801 were seen in the CA1 and dentate gyrus regions of the hippocampus. These studies indicate that robust increases in NMDA receptor binding do not occur with several chronic ethanol treatment protocols, and suggests that NMDA receptor supersensitivity during the development of tolerance and dependence to ethanol may not simply be due to changes in the density of NMDA receptors, but may involve other mechanisms.

Topics: 2-Amino-5-phosphonovalerate; Alcoholism; Animals; Binding, Competitive; Brain; Brain Mapping; Dizocilpine Maleate; Male; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate

Synaptic plasma membranes were prepared from four cerebrocortical areas from six male Angora goats made chronically thiamine deficient (TD) by the administration of AmproliumTM (600-900 mg/kg daily for 38-44 d). Four male controls were matched for age (27-30 mo). Four different radioligands were used to characterise GABAA and Glu-RNMDA receptor binding sites. There were marked, localised and contrasting changes in motor cortex, with an increase in GABAA and a decrease in Glu-RNMDA binding site densities. Less clearcut changes of a similar nature were seen in visual cortex. There was no variation in the parameters of GABA-activated [3H]diazepam binding between cortical areas in control goats, but there was a reduction in the maximal response to GABA in all areas in TD goats. There were regional variations in glutamate-activated [3H]MK-801 binding in control goat brain, and a non-selectively reduced maximal response in TD. Alterations in these indices of GABA- and glutamate-mediated neurotransmission may underlie the neurological signs of acute thiamine deficiency in these animals.

Topics: Alcoholism; Amprolium; Animals; Brain Chemistry; Diazepam; Disease Models, Animal; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; Flunitrazepam; GABA Agonists; GABA Modulators; gamma-Aminobutyric Acid; Goats; In Vitro Techniques; Male; Muscimol; Receptors, GABA-A; Receptors, N-Methyl-D-Aspartate; Synaptic Membranes; Synaptosomes; Thiamine Deficiency

Chronic ethanol treatment of mice has been shown to result in increased binding of dizocilpine and glutamate to hippocampal NMDA receptors. These changes were suggested to reflect an increase in NMDA receptor number that may underlie certain signs of the ethanol withdrawal syndrome. However, there was no change in binding of a competitive NMDA receptor antagonist, or of ligand binding to the glycine co-agonist site on the receptor after chronic ethanol treatment. Differential changes in the binding of particular ligands at the NMDA receptor suggested the possibility that chronic ethanol ingestion might selectively affect the expression of particular NMDA receptor subunits. Our current work demonstrates that chronic ethanol ingestion by mice, which results in the generation of physical dependence, also produces increases in the NMDA receptor NR1 subunit protein in the hippocampus and cerebellum (approximately 50% and 95%, respectively), and produces increases in the NR2A subunit protein in the hippocampus and cortex (approximately 25% and 40%, respectively). However, the mRNA levels for these subunits were not increased in the respective brain areas by the same ethanol treatment. The changes in NMDA receptor subunit expression in discrete areas of the brain may contribute to the previously observed changes in ligand binding and, possibly, signs of ethanol withdrawal.

Topics: Alcoholism; Animals; Brain; Cerebellum; Cerebral Cortex; Dizocilpine Maleate; Glutamic Acid; Hippocampus; Macromolecular Substances; Male; Mice; Mice, Inbred C57BL; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Substance Withdrawal Syndrome

During repeated alcohol withdrawal, convulsive withdrawal behavior has been shown to be increased in a kindling-like manner in both clinical and experimental studies. In the present experiment, quantitative autoradiography was used to investigate binding of tritiated ligands to glutamate receptor subtypes and the benzodiazepine/GABA (BZ/GABA) receptor complex in rats exposed to 14 episodes of alcohol withdrawal. Seizures were detected in 25% of the animals during withdrawal episode 10-13. Repeated alcohol withdrawal resulted in a decrease in the number of [3H]-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid ([3H]-AMPA) binding sites in striatum and sub-regions of the entorhinal cortex, the cerebellum and the hippocampus, while the [3H]-flunitrazepam binding was down-regulated in the frontal cortex. There was no differences between the controls and the multiple withdrawal animals regarding the [3H]-dizocilpine ([3H]-MK801) binding and the [3H]-kainic acid binding. However, within the latter group, those animals in which withdrawal seizures were observed had increased [3H]-MK801 binding sites in focal regions of entorhinal cortex and hippocampus, compared to those in which seizures were not observed. The decreased AMPA binding suggested impaired glutamate neurotransmission. As such, this receptor probably did not contribute to alcohol withdrawal kindling, but rather was involved in seizure protective mechanisms during this process.

Topics: Alcoholism; Animals; Autoradiography; Brain; Dizocilpine Maleate; Down-Regulation; Ethanol; Excitatory Amino Acid Antagonists; Flunitrazepam; GABA Modulators; Kindling, Neurologic; Male; Rats; Rats, Wistar; Receptors, GABA-A; Receptors, Glutamate; Receptors, Kainic Acid; Seizures; Substance Withdrawal Syndrome

The present study investigated whether temperature-related changes in NMDA receptor sensitivity to ethanol might play a role in mediating the effects of body temperature on behavioral sensitivity to ethanol or in determining genotypic differences in sensitivity to ethanol. We accomplished this by determining the effects of ethanol on three different mouse genotypes (C57, LS, and SS) on two types of NMDA receptor-mediated responses at 30 degrees and 35 degrees C: (i) extracellularly recorded synaptic potentials elicited in the CA1 region of the in vitro hippocampal slice preparation by stimulation of the Schaffer-commisural pathway in the presence of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor blocker, 6,7-dinitroquinoxaline-2,3-dione, and low magnesium concentration; and (ii) increase in [3H]MK-801 binding elicited by glutamate in telencephalic membrane preparations. Ethanol significantly decreased NMDA receptor-mediated excitatory postsynaptic potential (EPSP) amplitude and area in the three genotypes. In C57, the effect of ethanol on NMDA receptor-mediated EPSP amplitude and area was more pronounced at 30 degrees C, compared with that at 35 degrees C. In most cases, there was a good correlation between the effects of ethanol on EPSP amplitude and area. The order of sensitivity between the three genotypes was C57 = LS > SS at 35 degrees C and C57 > LS = SS at 30 degrees C. Similarly, ethanol significantly decreased glutamate-stimulated [3H]MK-801 binding in membrane fractions. The effect of ethanol was temperature-dependent, because ethanol produced more inhibition at 30 degrees C than at 35 degrees C in all genotypes. The effect of ethanol on MK-801 binding was concentration-dependent, and the sensitivity to 100 mM ethanol of the genotypes at 35 degrees C was LS > SS = C57, whereas it was SS > LS = C57 at 30 degrees C. Collectively, the results demonstrate that temperature is an important variable that can influence NMDA receptor sensitivity to ethanol measured via electrophysiological and binding techniques, and that temperature can influence relative sensitivity of NMDA receptors to ethanol between mouse genotypes. Furthermore, the findings indicate that temperature-induced changes in sensitivity of NMDA receptors to ethanol may play a role in mediating the effects of body temperature on behavioral sensitivity to ethanol in LS, but not C57 and SS mice.

Topics: Alcoholism; Animals; Body Temperature; Culture Techniques; Dizocilpine Maleate; Ethanol; Genotype; Hippocampus; Mice; Mice, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Sleep

Ethanol, acutely, is a potent inhibitor of the function of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor. After chronic exposure of animals to ethanol, however, the NMDA receptor in brain is upregulated. This upregulation is associated with the occurrence of ethanol withdrawal seizures. When cultured cerebellar granule neurons are exposed chronically to ethanol, the resulting upregulation of NMDA receptor function renders the cells more susceptible to glutamate-induced neurotoxicity. The present studies show that chronic ethanol exposure produces an increase in NMDA receptor number in the cells, measured by ligand binding to intact cells. Glutamate-induced excitotoxicity, both in control and ethanol-exposed cells, is blocked by the same NMDA receptor antagonists previously shown to block ethanol withdrawal seizures in animals. In addition, glutamate neurotoxicity is blocked by acute (2-hr) pretreatment of cells with ganglioside GM1 or by chronic (3 days) treatment with the ganglioside. Acute ganglioside treatment does not interfere with the initial rise in intracellular calcium caused by glutamate, whereas this response is downregulated after chronic ganglioside treatment. These results suggest that therapeutic agents can be developed to block both ethanol withdrawal signs and the neuronal damage that accompanies ethanol withdrawal. Furthermore, chronic ganglioside treatment during ethanol exposure has the potential to prevent changes in the NMDA receptor that lead to withdrawal seizures and enhanced susceptibility to excitotoxicity.

Topics: Alcohol Withdrawal Delirium; Alcoholism; Animals; Animals, Newborn; Cells, Cultured; Cerebellum; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Female; G(M1) Ganglioside; Glutamic Acid; Kynurenic Acid; Neurons; Pipecolic Acids; Rats; Receptors, N-Methyl-D-Aspartate; Synaptic Transmission; Up-Regulation

Previous work has demonstrated that short periods (1-2 weeks) of exposure to ethanol produce an upregulation of the N-methyl-D-aspartate (NMDA) receptor complex in hippocampus; an alteration that appears to be associated with the development of physical dependence, because a return to control levels occurs over a 24- to 48-hr abstinence period. Prolonged periods of chronic ethanol treatment (CET; 4-8 months of treatment) have been shown to produce severe and permanent alterations in the morphological and functional characteristics of hippocampal pyramidal neurons. Several lines of research have demonstrated that the NMDA receptor complex is involved in excitotoxic cell loss during certain pathological states. On the basis of this evidence, we hypothesized that prolonged ethanol exposure would be accompanied by an enduring increase in NMDA receptors and that NMDA receptor binding in cells surviving CET would be altered. To test this hypothesis, we measured the binding characteristics of the NMDA receptor complex in a variety of brain structures following CET. Animals were fed a nutritionally complete, ethanol-containing diet for 28 weeks and then allowed a 48-hr abstinence period. A control group was fed the same diet, except sucrose was isocalorically substituted for ethanol. We first examined the effect of CET on the binding properties of a noncompetitive antagonist to the NMDA receptor channel, [3H]diclozipene ([3H]MK-801). Next, as an indirect examination of NMDA receptor function, we measured the ability of glutamate to stimulate channel opening and thus [3H]MK-801 binding. In all brain structures examined, neither the Kd nor the Bmax of [3H]MK-801 binding to the NMDA receptor was altered following CET. In addition, no effect of treatment was seen on the ability of glutamate to stimulate [3H]MK-801 binding.

Topics: Alcoholism; Animals; Autoradiography; Dizocilpine Maleate; Glutamic Acid; Hippocampus; Male; Mental Recall; Rats; Receptors, N-Methyl-D-Aspartate; Up-Regulation

The selectively bred alcohol-preferring (P) and alcohol-nonpreferring (NP) rats have been shown to possess a number of behavioral and electrophysiological differences in response to alcohol. We sought to evaluate whether or not P and NP rats would respond differently to other sedative-hypnotic drugs related to ethanol. EEG recordings were conducted following systemic administration of the NMDA receptor antagonist MK 801 (0.1 mg/kg, ip) and the GABA/benzodiazepine receptor complex agonist diazepam (1.5 mg/kg, ip). Nine P and nine NP rats was implanted with bipolar stainless steel electrodes in the frontal cortex, the dorsal hippocampus, the ventral thalamus, and the anterior amygdala. In the vehicle condition, P rats showed significantly greater power of the EEG in the slow frequencies as compared with NP rats in the frontal cortex. Furthermore, P rats were found to have lower peak theta frequency (6-8 Hz) than NP rats in the frontal cortex, the dorsal hippocampus, and the ventral thalamus. MK 801 produced a significantly greater increase in the mean power of the EEG in NP rats in the 8-16 Hz than in P rats, whereas diazepam was found to decrease theta peak frequency (6-8 Hz), but more so in NP rats that in P rats. These data suggest that, in addition to differential responsiveness to alcohol, P and NP rats also differ in response to drugs that modify GABA and glutamate neurotransmission.

Topics: Alcoholism; Amygdala; Animals; Diazepam; Dizocilpine Maleate; Electroencephalography; Ethanol; Frontal Lobe; Hippocampus; Injections, Intraperitoneal; Male; Rats; Rats, Inbred Strains; Receptors, GABA-A; Receptors, N-Methyl-D-Aspartate; Thalamus

Recent studies have shown that alterations in gamma-aminobutyric acid (GABAA) and N-methyl-D-aspartate (NMDA) receptor subunit mRNA levels are associated with the effects of chronic ethanol exposure as well as genetic selection for ethanol withdrawal seizure sensitivity. We have previously shown that chronic ethanol exposure in rats results in a decrease in the levels of GABAA receptor alpha 1 and alpha 2 subunit mRNAs in cerebral cortex, an increase in the levels of alpha 6 subunit mRNAs in cerebellum and no alteration in alpha 3, GAD, ribosomal RNA or polyA + RNA levels in these regions. Since chronic ethanol administration increases the expression of [3H]Ro15-4513 binding sites in cortex and cerebellum with no effect on other GABAA receptor recognition sites, we hypothesized that the expression of other subunits would be altered in these regions. In addition, since ethanol appears to interact with zolpidem-sensitive GABAA receptors in rat brain, we investigated the effect of chronic ethanol administration on these recognition sites. Chronic ethanol administration increased [3H]zolpidem binding with no effect on levels of GABAA receptor beta 2 and gamma 2 subunit mRNAs. In addition, we examined the levels of NMDAR1 receptor subunit mRNAs since chronic ethanol administration results in increased levels of [3H]MK-801 recognition sites on NMDA receptors. NMDAR1 receptor subunit mRNAs were not altered following chronic ethanol exposure in rat cortex or hippocampus. These studies underscore the specificity of ethanol interactions with these receptors and the importance of understanding the mechanisms of both GABAA and NMDA receptor regulation in elucidating the etiology of ethanol dependence.

Topics: Alcoholism; Animals; Azides; Base Sequence; Benzodiazepines; Cerebellum; Cerebral Cortex; Dizocilpine Maleate; DNA, Complementary; Gene Expression; Hippocampus; Male; Pyridines; Rats; Rats, Sprague-Dawley; Receptors, GABA-A; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Seizures; Substance Withdrawal Syndrome; Zolpidem

Ethanol (EtOH) administration is considered to elicit its reinforcing properties by stimulating dopaminergic (DA) transmission in the mesolimbic system. Accordingly, (EtOH) activates dopamine neuronal firing in the Ventro-Tegmental Area (VTA) and DA output in the nucleus accumbens. Concomitantly, EtOH reduces the firing rate of Pars Reticulata (PR) neurons which are thought to exert an inhibitory control over DA neurons. Further, chronic ingestion of EtOH produces tolerance to its sedative effects as to the depressant effect on PR neurons but no tolerance to the DA stimulating action. Moreover the NMDA antagonist MK-801, but not SL-820715, stimulates DA firing, suggesting that this effect is not a general characteristic of NMDA receptor antagonists and questioning the possibility that NMDA-receptor blockade may underlie EtOh-induced activation of DA-ergic transmission. The results indicate that activation of the mesolimbic DA tract is essential in the rewarding properties of EtOH and that neither GABA-ergic inhibition nor NMDA-receptor blockade by EtOH, are causally linked to the EtOH-induced activation of DA-ergic transmission.

Topics: Alcoholism; Animals; Aversive Therapy; Dizocilpine Maleate; Dopamine; Electrophysiology; Ethanol; gamma-Aminobutyric Acid; Glutamic Acid; Limbic System; Male; Piperidines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Reward; Synaptic Transmission

The expression of c-fos mRNA in rat brain was induced by intraperitoneal (ip) administration of N-methyl-D-aspartate (NMDA) and kainic acid, agonists of different classes of glutamate receptors and by caffeine, an antagonist of adenosine receptors. The actions of NMDA but not kainic acid or caffeine were blocked by ethanol. Chronic exposure to ethanol vapour did not increase c-fos expression. However, ethanol-withdrawn rats showed a marked increase in c-fos expression. In situ hybridisation and immunohistochemistry indicated the expression was widely distributed in the brain but particularly in the cortex, hippocampus and the cerebellum. There was no marked change in the sensitivity of the NMDA receptor to inhibition by ethanol after chronic ethanol treatment. The withdrawal-induced expression of c-fos mRNA could be inhibited by prior administration of MK801. These results emphasise the NMDA receptor as an important site of ethanol action and the potential use of immediate early gene expression in neuropharmacology in vivo.

Topics: Alcoholism; Animals; Brain; Caffeine; Dizocilpine Maleate; Ethanol; Gene Expression Regulation; Genes, fos; Genes, Immediate-Early; Kainic Acid; Male; N-Methylaspartate; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate; RNA, Messenger; Substance Withdrawal Syndrome; Tissue Distribution

The effect of long-term treatment with ethanol was investigated on the function of gamma-aminobutyric acid A (GABAA) and N-methyl-d-aspartic acid (NMDA) receptors. Rats were rendered ethanol-dependent by repeated forced administration of a 20% ethanol solution (12 to 18 g/kg/day po) for 6 days and tested while still intoxicated or at different time intervals after withdrawal. t-[35S]Butylbicyclophosphorothionate (35S-TBPS) binding was increased by 30% in cortical homogenates of rats killed 1 to 3 hr after last ethanol administration, when compared with saline-treated animals. However, GABA-stimulated 36Cl- uptake and its enhancement by flunitrazepam was decreased in the ethanol-treated animals. 35S-TBPS binding and 36Cl- influx measured 9 to 24 hr following the last ethanol injection, when withdrawal signs were present, were unmodified with respect to saline-treated rats. Moreover, the effects of both isoniazid and FG 7142 on 35S-TBPS binding were unchanged in ethanol-dependent rats tested at 1 to 3 and 9 to 24 hr, compared with controls. In contrast, ethanol-withdrawn rats tested at 9 to 24 hr showed a dramatic enhancement in their sensitivity to the convulsant action of isoniazid (50 to 250 mg/kg, sc). The same animals were also more susceptible to the convulsant action of NMDA (0.5 to 5 micrograms/5 microliters/rat intracerebroventricularly) and kainic acid (12 mg/kg, ip), and this effect was paralleled by an enhancement (+25%) in the density of 3H-MK 801 recognition sites in the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Alcohol Withdrawal Delirium; Alcoholism; Animals; Brain; Bridged Bicyclo Compounds; Bridged Bicyclo Compounds, Heterocyclic; Chloride Channels; Convulsants; Dizocilpine Maleate; Ethanol; Isoniazid; Kainic Acid; Male; Membrane Proteins; N-Methylaspartate; Rats; Rats, Sprague-Dawley; Receptors, GABA-A; Receptors, N-Methyl-D-Aspartate; Seizures; Synaptic Transmission

The effects of ethanol on the binding of [3H]MK-801, [3H]L-glutamate, [3H]glycine and [3H]CGS 19755 to the N-methyl-D-aspartate receptor were determined in membranes from mouse cortex and hippocampus. Under equilibrium conditions, ethanol in vitro (100 mM) did not alter the apparent affinity or binding site density for any of these ligands. However, in the presence of glutamate and the selective glycine antagonist, 5,7-dichlorokynurenic acid, ethanol inhibited the non-equilibrium binding of [3H]MK-801. This inhibition could be reversed in a time- and concentration-dependent manner by addition of glycine. These data suggest that ethanol may inhibit N-methyl-D-aspartate receptor-mediated responses by altering the kinetics of channel activation. Chronic in vivo ethanol ingestion by mice, that resulted in tolerance to and physical dependence on ethanol, produced an increased density of hippocampal [3H]MK-801 and [3H]L-glutamate binding sites, but not [3H]glycine or [3H]CGS 19755 binding sites. It is possible that chronic ethanol ingestion may influence the subunit composition of the NMDA receptor complex.

Topics: Alcoholism; Animals; Dizocilpine Maleate; Ethanol; In Vitro Techniques; Kainic Acid; Male; Mice; Mice, Inbred C57BL; Radioligand Assay; Receptors, N-Methyl-D-Aspartate; Sensitivity and Specificity; Up-Regulation

Recent evidence indicates involvement of excitatory amino acid receptors sensitive to N-methyl-d-aspartate (NMDA) in the action of ethanol (EtOH). Pronounced inhibition of NMDA receptor function is seen in vitro with concentrations of EtOH corresponding to those present during alcohol intoxication in humans. The present study was devoted to investigate the role of NMDA receptors in the action of EtOH in rats. Acute experiments showed antagonism by EtOH of convulsions induced by intracerebroventricular injection of NMDA. A similar effect was seen with a high dose of diazepam. Convulsions induced by an agonist of another excitatory amino acid receptor subtype, kainate, were also inhibited by EtOH. An uncompetitive antagonist of NMDA receptors, 5-methyl-10,11-dihydro-5H-dibenzocyclohepten-5,10-imine maleate (MK-801), potentiated EtOH-induced loss of righting, but attenuated the hypothermic action of EtOH. Moreover, MK-801 inhibited audiogenic convulsions in EtOH withdrawn rats. At the same time the effect of a proconvulsive dose of NMDA was not enhanced. Tolerance to the myorelaxant action of both EtOH and MK-801 upon repetitive administration was seen. Also some degree of cross-tolerance was observed. Moreover, MK-801 failed to modify EtOH preference in rats. The present results support involvement of NMDA receptors in expression of some acute and subchronic actions of EtOH and in expression of EtOH withdrawal.

Topics: Alcohol Drinking; Alcoholic Intoxication; Alcoholism; Animals; Binding, Competitive; Body Temperature Regulation; Brain; Dizocilpine Maleate; Ethanol; Male; Muscle Relaxation; Postural Balance; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate; Reflex; Seizures

Prior biochemical and electrophysiological studies have shown that low doses of ethanol inhibited calcium influx through the N-methyl-D-aspartate (NMDA) receptor/ionophore. The present data show that chronic ethanol treatment results in an increase in the number of NMDA receptor/ionophore complexes in the hippocampus, a brain area known to be associated with ethanol withdrawal seizure activity. Treatment during withdrawal with NMDA-exacerbated handling induced withdrawal seizures in the ethanol-dependent mice, while administration of the NMDA receptor-associated calcium channel antagonist MK-801 decreased the occurrence and severity of the withdrawal seizures in a dose-dependent manner. The results are consistent with the hypothesis that the up-regulation of the NMDA receptor systems following chronic ethanol treatment may mediate the seizures associated with ethanol withdrawal in dependent animals.

Topics: Alcoholism; Animals; Behavior, Animal; Dibenzocycloheptenes; Diet; Dizocilpine Maleate; Ethanol; Hippocampus; Male; Mice; Mice, Inbred C57BL; Receptors, N-Methyl-D-Aspartate; Receptors, Neurotransmitter; Seizures; Substance Withdrawal Syndrome