Neuronal Degeneration in Rat Cerebrocortical and Olfactory Regions During Subchronic "Binge" Intoxication with Ethanol: Possible Explanation for Olfactory Deficits in Alcoholics

Severe, repetitive (“binge”) ethanol intoxication in adult rats (intragastric delivery 3 times daily for 4 days in a modification of the Majchrowicz method) precipitates neuronal degeneration in selected cerebral cortical regions involved in memory and olfaction, confirming the results of Switzer and colleagues (Anat. Rec. 202 186a, 1982). Neuronal damage was visualized with the de Olmos cupric silver technique for degenerating neurons and processes (argyrophilia), and was quantitated by total counts and densities of argyrophilic cells/fields. The specificity of the degeneration provides a neuropathological basis for the olfactory memory deficits in chronic alcoholics. In highly intoxicated rats, argyrophilia was most extensive among hippocampal dentate gyrus granule cells, pyramidal neurons in layer 3 of the entorhinal cortex, and olfactory nerve terminals in the olfactory bulb. Degenerating pyramidal neurons were also consistently seen in the insular cortex and olfactory cortical regions, such as the piriform and perirhinal cortices. There were few argyrophilic neurons in the CA regions of the hippocampus and none in the cerebellum—regions generally shown to have cell loss in long-term ethanol feeding models—but degenerating mossy fibers in the CA2 region were observed. Degeneration was maximal before the peak period of abstinence symptoms in this model, because argyrophilic densities were no greater36 hr, compared with 8 hr after the last ethanol dose. High blood ethanol levels were required, because argyrophilia, absent from isocaloric controls, also was only evident in ethanol-intoxicated rats with mean blood ethanol levels for days 2 to 4 above 300 mg/dl; however, it increased substantially between 350 and 550 mg/dl. The resemblance of the argyrophilic distribution to the regional neuropathology that occurs in experimental seizures indicates that the ethanol-induced degeneration may have an excitotoxic basis. Progressive reductions in the seizure threshold (e.g., kindling phenomena that have been documented during binge ethanol intoxication) might be associated with excitotoxic hyperactivity during the repetitive nadirs between high blood and brain ethanol peaks. However, direct toxic actions of ethanol or its metabolites could also be involved. Overall, the model should be useful for studying mechanisms of ethanol-induced selective cortical and olfactory brain damage.     

Administration of low doses of MK-801 during ethanol withdrawal in the developing rat pup attenuates alcohol's teratogenic effects

BACKGROUND: Alcohol exposure during development can produce severe and long-lasting central nervous system damage and consequent behavioral alterations. Recent evidence suggests that NMDA receptor-mediated excitotoxicity during periods of withdrawal may contribute to this damage. We have demonstrated that blocking the NMDA receptor with MK-801 during alcohol withdrawal can attenuate ethanol's adverse effects on behavioral development in the rat. This study examined the dose dependency of MK-801's ability to mitigate ethanol's teratogenic effects. METHODS: Neonatal rat pups were exposed to 6.0 g/kg of ethanol in a binge-like manner on postnatal day (PD) 6, a period of brain development equivalent to a portion of the human third trimester. Alcohol administration was accomplished with an artificial rearing procedure. Twenty-one hours after ethanol treatment, pups were injected intraperitoneally with one of four doses of MK-801 (0.05, 0.1, 0.5, or 1.0 mg/kg) or saline vehicle. An artificially reared control and a normally reared control group were included. On PD 18-19, activity level was monitored, and on PD 40-42, serial spatial discrimination reversal learning was assessed. RESULTS: Alcohol exposure on PD 6 produced significant increases in activity level and deficits in reversal learning. These alcohol-induced behavioral alterations were significantly attenuated in subjects treated with one of the three lower doses (0.05-0.5 mg/kg) of MK-801 during withdrawal. The performance of ethanol-exposed subjects treated with the high dose of MK-801 (1.0 mg/kg) did not differ from that of the Ethanol Only group. CONCLUSIONS: These data suggest that alterations in NMDA receptor activation during alcohol withdrawal contribute to the neuropathology and consequent behavioral alterations associated with developmental alcohol exposure. These data have important implications for pregnant women and newborns undergoing ethanol withdrawal.     

Binge Ethanol-Induced Brain Damage in Rats: Effect of Inhibitors of Nitric Oxide Synthase

Testing the possible role of endogenous nitric oxide (NO) in the neurotoxicity of ethanol, we examined how two different NO synthase (NOS) inhibitors affected the extent of cerebrocortical and olfactory neuronal damage in a modified "binge intoxication" rat model (Collins et al., Alcohol Clin. Exp. Res. 20:284–292, 1996). Male rats intragastrically fed ethanol (6.5 to 12 g/kg/day) in nutrient solution three times daily for 4 days also received N^G-nitro-L-arginine methyl ester by chronic intracerebroventricular infusion or 7-nitro-indazole by daily intraperitoneal injection; control rats were given nutrient solution only and/or vehicles. Blood ethanol levels did not differ among the ethanol-treated groups. The amount of ethanol-dependent neuronal degeneration in the entorhinal cortex, dentate gyrus, and olfactory bulb glomeruli—visualized with the de Olmos cupric silver stain and quantitatively assessed in the binge-intoxicated rats—was either unchanged or significantly increased by the NOS inhibitors. Although the efficacies of the inhibitors cannot be directly compared because various NOS forms were probably inhibited to differing extents, the results do not support the idea that endogenous NO is a neurotoxic mediator of ethanol's effects. Rather, NO may have a modest neuroprotectant role in this model of early brain damage induced by ethanol. In addition, the NOS that is localized histochemically as NADPH diaphorase was present primarily in regions and/or cells not damaged by binge ethanol treatment. Assuming that NADPH diaphorase represents most of the NO forming enzyme(s), this suggests a transcellular mechanism for NO. A further observation was that hippocampal CA pyramidal neuron degeneration was extensive in rats infused centrally with N^G-nitro-L-arginine methyl ester.     

Alcohol-Induced Neuronal Loss in Developing Rats: Increased Brain Damage with Binge Exposure

A rat model of third trimester fetal alcohol exposure was used to determine whether a smaller daily dose of alcohol can induce more severe microencephaly and neuronal loss than a larger dose, if the small dose is consumed in such a way that it produces higher blood alcohol concentrations (BACs). The possibility of regional differences within the developing brain to alcohol-induced neuronal loss was also investigated. Sprague-Dawley rat pups were reared artificially over postnatal Days 4-10 (a period of rapid brain growth similar to that of the human third trimester). Two groups received a daily alcohol dose of 4.5 g/kg, administered either as a 5.1% solution in four of the 12 daily feedings or as a 10.2% solution in two of the 12 feedings. A third group received a higher daily dose (6.6 g/kg) administered as a 2.5% solution in every feeding. Gastrostomy and suckle controls were also reared. On postnatal Day 10, the animals were perfused, and brain weights were obtained. In the hippocampal formation, cell counts were made of the pyramidal cells of fields CA1 and CA2/3, the multiple cell types of CA4 and the granule cells of the dentate gyrus. In the cerebellum, Purkinje cells and granule cells were counted in each of the ten lobules of the vermis. The lower daily dose (4.5 g/kg) condensed into two or four feedings produced high maximum BACs (means of 361.6 and 190.7 mg/dl, respectively) and significant microencephaly and cell loss, relative to controls. The higher daily dose (6.6 g/kg), administered continuously, resulted in low BACs (mean of 39.2 mg/dl) and induced no microencephaly or cell loss. Regional differences in neuronal vulnerability to alcohol were evident. In the hippocampus, CA1 neuronal number was significantly reduced only by the most condensed alcohol treatment, while CA3, CA4, and the dentate gyrus populations were not reduced with any alcohol treatment. In the cerebellum, some lobules suffered significantly greater Purkinje cell loss and granule cell loss than did others. The regions in which Purkinje cells were most mature at the time of the alcohol exposure were the most vulnerable to Purkinje cell loss.     

Binge ethanol consumption causes differential brain damage in young adolescent rats compared with adult rats

BACKGROUND: Adolescents respond differently to alcohol than adults. Furthermore, binge drinking in young adolescents is becoming increasingly common. METHODS: To determine if the effects of binge drinking on brain damage are different in juveniles compared with adults, the effects of a 4 day binge ethanol treatment (e.g., 4 days of 4 times per day 15% ethanol intragastrically, approximately 9-10 g/kg/day ethanol) were investigated in adolescent-juvenile rats (JVN) 35 days old and compared with adult (ADT) rats 80 to 90 days old. Brain damage was measured by using the amino cupric silver stain of de Olmos et al. (1994). RESULTS: Significant brain damage was found in both groups. The olfactory bulbs were equally damaged in both groups; however, the associated frontal cortical olfactory regions were damaged only in JVN. The anterior portions of the piriform and perirhinal cortices also were damaged only in JVN rats. Quantitation of silver-stained frontal areas in binge ethanol-treated JVN rats ranged from 400% to 1,260% of control values. For example, in anterior perirhinal cortex, silver stain increased from 48 +/- 14 to 444 +/- 114 (mm2 x 10(3) argyrophilic area; p < 0.01) in JVN control and binge ethanol-treated animals, respectively. In contrast, posterior perirhinal cortex showed greater damage in adults, being 236 +/- 76 vs. 875 +/- 135 (mm2 x 10(3) argyrophilic area; p < 0.005) in JVN and ADT, respectively. CONCLUSIONS: The young-adolescent brain shows differential sensitivity to alcohol-induced brain damage compared with adults.     

N-methyl-D-aspartate receptor activity and estradiol: separate regulation of cell proliferation in the dentate gyrus of adult female meadow vole

We have previously found that estradiol increases (within 4 h) but then decreases (within 48 h) cell proliferation in the dentate gyrus of adult female ovariectomized (OVX) rats and of intact meadow voles and that estradiol partially stimulates adrenal activity to suppress cell proliferation in rats. Estradiol enhances N-methyl-D-aspartate receptor (NMDAr) activity and NMDAr activation suppresses cell proliferation in the adult rodent dentate gyrus. Therefore, we tested whether estradiol alters cell proliferation in the dentate gyrus of adult OVX female meadow voles by stimulating NMDAr activity. In experiment 1, OVX females were injected with estradiol (10 micro g) or oil and then with NMDA (30 mg/kg) or vehicle 3 h later and bromodeoxyuridine 4 h later (BrdU; 50 mg/kg). Voles were perfused 1 h after BrdU injection. Relative to oil vehicle, estradiol increased (P相似文献   

MK-801 can exacerbate or attenuate behavioral alterations associated with neonatal alcohol exposure in the rat, depending on the timing of administration

BACKGROUND: We have reported that administration of MK-801, an NMDA receptor antagonist, during ethanol withdrawal in the developing rat attenuates ethanol's adverse effects on behavioral development. In the present study, we altered the timing of MK-801 delivery in relation to the last alcohol dose to determine if its protective effects were specific to the ethanol withdrawal phase. METHODS: Five groups of rats were artificially reared and exposed to alcohol in a binge-like manner on postnatal day (PD) 6, producing peak blood alcohol levels of 335 mg/dl that cleared to 0 mg/dl by 33 hours. Four groups received MK-801 at various times after alcohol treatment (0, 9, 21, or 33 hr post-ethanol). The fifth alcohol-treated group received saline. Two artificially reared control groups were included: one was injected with saline and the other injected with 0.5 mg/kg MK-801. Finally, a normally reared suckle control group was also included. Activity level and performance on a spatial discrimination reversal-learning task were evaluated at PD 18 and PD 40, respectively. RESULTS: Administration of MK-801 at the same time as ethanol treatment (0 hr) produced a high rate of mortality. Ethanol exposure on PD6 increased activity level relative to controls. Administration of MK-801 at 0 hr exacerbated this ethanol-induced overactivity, whereas administration of MK-801 at 21 and 33 hr reduced the severity of ethanol-related overactivity. Similarly, ethanol exposure on PD 6 significantly increased the number of errors committed on a spatial discrimination reversal-learning task. MK-801 injections 9 hrs after ethanol exacerbated this effect, whereas MK-801 treatment 33 hrs after ethanol attenuated this effect. Thus, MK-801 administration at the time of ethanol treatment was highly toxic, whereas during the withdrawal period it was protective. CONCLUSION: These data are consistent with the hypothesis that ethanol exposure in the neonatal rat inhibits the NMDA receptor, producing a subsequent rebound in NMDA receptor activation and possible excitotoxicity during withdrawal. Both the acute inhibitory effects of ethanol and the excitatory effects of withdrawal may contribute to fetal alcohol effects.     

Reduced seizure threshold and hippocampal cell loss in rats exposed to alcohol during the brain growth spurt

BACKGROUND: Epilepsy is a prominent sign of neurologic dysfunction in some children with fetal alcohol syndrome (FAS). However, it is unknown whether the epileptic disorders in these children are directly due to the neuroteratogenic effects of alcohol or to some other factor accompanying maternal alcoholism. The hippocampus is vulnerable to alcohol-induced pathologic changes, and dysfunction of the hippocampus often manifests as epilepsy. We examined the effect of alcohol exposure during development on the seizure threshold and examined the relationship between alteration of seizure threshold and alcohol-induced neuronal loss from the hippocampus. METHODS: Rat pups received 0.85, 2.5, or 3.75 g/kg of alcohol via intragastric intubation daily over postnatal days (PD) 4-9. An intubated control and a suckle control group were also included. To assess the effect of a single day of alcohol exposure, an additional group received 3.75 g/kg of alcohol on PD 4 alone. Behavioral seizure thresholds were determined by intravenous infusion of the proconvulsant, pentylenetetrazol (PTZ), on PD 31 or on PD 90. In addition, electrographic seizure thresholds were determined by recording extracellular field potentials from the dentate gyrus. The number of hippocampal CA1 pyramidal cells, CA3 pyramidal cells, and granule cells of the dentate gyrus were determined by stereology. RESULTS: Daily exposure to alcohol resulted in a dose-dependent decrease in the seizure threshold and in the selective loss of CA1 pyramidal cells. Reduction in the seizure threshold was significantly correlated with loss of CA1 pyramidal cells. Recordings of extracellular field potentials confirmed the alcohol-induced reduction in seizure threshold, demonstrated that PTZ-induced seizures involve hippocampal-parahippocampal circuitry, and provided evidence that the hippocampal formation is the generator of the PTZ-induced seizures in alcohol-exposed animals. CONCLUSIONS: These findings demonstrate that exposure of the developing brain to alcohol can permanently reduce the threshold for both behavioral and electrographic seizures and can selectively kill hippocampal CA1 pyramidal cells. Both the pathologic findings and the physiologic recordings support the concept that the reduced seizure threshold in alcohol-exposed animals is due to hippocampal pathology.     

Neuroprotective effects of melatonin on amphetamine‐induced dopaminergic fiber degeneration in the hippocampus of postnatal rats

Chronic amphetamine (AMPH) abuse leads to damage of the hippocampus, the brain area associated with learning and memory process. Previous results have shown that AMPH‐induced dopamine neurotransmitter release, reactive oxygen species formation, and degenerative protein aggregation lead to neuronal death. Melatonin, a powerful antioxidant, plays a role as a neuroprotective agent. The objective of this study was to investigate whether the protective effect of melatonin on AMPH‐induced hippocampal damage in the postnatal rat acts through the dopaminergic pathway. Four‐day‐old postnatal rats were subcutaneously injected with 5‐10 mg/kg AMPH and pretreated with 10 mg/kg melatonin prior to AMPH exposure for seven days. The results showed that melatonin decreased the AMPH‐induced hippocampal neuronal degeneration in the dentate gyrus, CA1, and CA3. Melatonin attenuated the reduction in the expression of hippocampal synaptophysin, PSD‐95, α‐synuclein, and N‐methyl‐D‐aspartate (NMDA) receptor protein and mRNA caused by AMPH. Melatonin attenuated the AMPH‐induced reduction in dopamine transporter (DAT) protein expression in the hippocampus and the reduction in mRNA expression in the ventral tegmental area (VTA). Immunofluorescence demonstrated that melatonin not only prevented the AMPH‐induced loss of DAT and NMDA receptor but also prevented AMPH‐induced α‐synuclein overexpression in the dentate gyrus, CA1, and CA3. Melatonin decreased the AMPH‐induced reduction in the protein and mRNA of the NMDA receptor downstream signaling molecule, calcium/calmodulin‐dependent protein kinase II (CaMKII), and the melatonin receptors (MT1 and MT2). This study showed that melatonin prevented AMPH‐induced toxicity in the hippocampus of postnatal rats possibly via its antioxidative effect and mitochondrial protection.     

The N-methyl-D-aspartate receptor antagonist MK-801 delays the onset of puberty and may acutely block the first spontaneous LH surge and ovulation in the rat.

The physiological role of activated hypothalamic N-methyl-D-aspartate (NMDA) receptors during the final phase of female sexual maturation was explored in the rat. The effects of administration of the specific non-competitive receptor antagonist MK-801 on the occurrence of first ovulation and on LH secretion were studied. Injections of MK-801 (0.1-0.2 mg/kg body wt, s.c.) were given once or twice daily, starting at 28 or 35 days of age and continuing up to the day of first ovulation, resulted in a significant delay of this ovulation. Rats that were treated daily with 0.2 mg MK-801/kg, starting on days 30 or 34 and continuing up to day 38, but not including the day of first pro-oestrus, also showed retarded first ovulation. No decrease in serum LH concentration, compared with control rats, could be detected in these rats. Acute treatment with MK-801 (one or two injections of 0.2, or one injection of 0.5 mg/kg) given at 11.30 h (and 16.00 h) on the day of first pro-oestrus produced partial (1 x 0.2 mg/kg) or complete (2 x 0.2 and 1 x 0.5 mg/kg) blockade of first ovulation; blocked rats ovulated 1 day later. Serum LH concentrations at 16.00 h on the day of pro-oestrus were significantly decreased in all MK-801-treated groups compared with saline-injected control rats. At 19.00 and 22.00 h LH concentrations remained low in all non-ovulating MK-801-treated rats, but increased in the MK-801-treated rats and ovulated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise Neuroprotection in a Rat Model of Binge Alcohol Consumption

Background: Excessive alcohol intake produces structural and functional deficits in corticolimbic pathways that are thought to underlie cognitive deficits in the alcohol use disorders (AUDs). Animal models of binge alcohol administration support the direct link of high levels of alcohol consumption and neurotoxicity in the hippocampus and surrounding cortex. In contrast, voluntary wheel running enhances hippocampal neurogenesis and generally promotes the health of neurons. Methods: We investigated whether voluntary exercise prior to binge alcohol exposure could protect against alcohol‐induced cell loss. Female Long‐Evans rats exercised voluntarily for 14 days before undergoing 4 days of binge alcohol consumption. Brains were harvested immediately after the last dose of alcohol and examined for various histological markers of neurodegeneration, including both cell death (FluoroJade B) and cell birth (Ki67) markers. Results: Rats that exercised prior to binge exposure were significantly less behaviorally intoxicated, which was not a result of enhanced hepatic metabolism. Rats that exercised prior to binge alcohol consumption had reduced loss of dentate gyrus granule cells and fewer FluoroJade B positive cells in the dentate gyrus and associated entorhinal‐perirhinal cortex compared to nonexercisers. However, exercise did not protect against cell death in the piriform cortex nor protect against alcohol‐induced decreases in cell proliferation, evidenced by a similar alcohol‐induced reduction in Ki67 labeled cells between exercise and sedentary rats. Conclusions: We conclude that exercise can reduce behavioral sensitivity to ethanol intoxication and protect vulnerable brain areas from alcohol‐induced cell death. Exercise neuroprotection of alcohol‐induced brain damage has important implications in understanding the neurobiology of the AUDs as well as in developing novel treatment strategies.     

Progesterone and prostaglandin H synthase-2 involvement in alcohol-induced preterm birth in mice

BACKGROUND: Recently, an association between alcohol consumption during pregnancy and shortened gestational length has been reported, but the underlying mechanisms remain unknown. Progesterone (P4) and prostaglandins have been shown to play important roles in parturition in both human and animal models. Recently, it has been suggested that prostaglandin H synthase-2 (PGHS-2) is responsible for prostaglandin changes associated with term and preterm labor. It is possible that alcohol induces preterm birth by altering P4 or PGHS-2 levels. These studies were designed to determine the role of P4 and PGHS-2 in alcohol-induced preterm labor in mice. METHODS: Experiment 1: Pregnant dams treated with either vehicle or alcohol (6 g/kg, intragastrically) on gestational day (GD) 16 were killed at various times in gestation up to the time of delivery. Plasma P4 levels were measured by radioimmunoassay and uterine PGHS-2 mRNA expression was measured by Ribonuclease Protection Assay. Results indicated that alcohol treatment was associated with an earlier decline in plasma P4 levels and an earlier rise in uterine PGHS-2 mRNA levels during gestation. Experiment 2: Pregnant C57BL/6J females were treated with either P4 (2.0 mg, subcutaneously) or vehicle (sesame oil) 2 hr before receiving either 6 g/kg alcohol (intragastrically) or vehicle (isocaloric sucrose) on gestational day (GD) 16. Results indicate that P4 pretreatment effectively antagonized alcohol-induced preterm delivery. Experiment 3: On GD16, pregnant dams received either 100 mg/kg nimesulide (a specific PGHS-2 inhibitor) or vehicle (saline) subcutaneously, 2 hr before treatment with either 6 g/kg alcohol (given intragastrically) or isocaloric sucrose. Nimesulide was effective in antagonizing alcohol-induced preterm labor. CONCLUSIONS: Together, these data suggest that both P4 and PGHS-2 may play roles in alcohol-induced preterm birth.     

MK-801 Administration During Ethanol Withdrawal in Neonatal Rat Pups Attenuates Ethanol-Induced Behavioral Deficits

Alcohol exposure during development can produce central nervous system dysfunction, resulting in a wide range of behavioral alterations. The various mechanisms by which alcohol causes these behavioral changes, however, remain unknown. One mechanism that has been suggested is NMDA receptor-mediated excitotoxic cell death produced by ethanol withdrawal. The present study examined whether MK-801, an antagonist of the NMDA receptor that has been shown to protect against NMDA receptor-mediated excitotoxicity, could block alcohol's adverse effects on behavior. Sprague-Dawley rat pups were exposed to alcohol (6.0 g/kg) in a binge-like manner on postnatal day 6 using an artificial rearing procedure. Subjects then received an injection of MK-801 (0.1 mg/kg) or vehicle during withdrawal, 21 hr after ethanol exposure. At postnatal day 40, all subjects were tested on a serial spatial discrimination reversal task. Ethanolexposed subjects were impaired in both discrimination and reversal learning, and committed a significantly greater number of perseverative-type errors, compared with controls. MK-801 administration during ethanol withdrawal significantly attenuated ethanol-induced deficits in reversal learning and increases in perseverative-type errors, whereas MK-801 exposure by itself had no significant effect on performance. Thus, exposure to MK-801 during ethanol withdrawal partially protected against alcohol-related disruptions in spatial reversal learning. These results support the suggestion that NMDA receptor-mediated excitotoxicity may be one mechanism by which alcohol induces behavioral teratogenicity.     

Increased salivary cortisol concentrations during chronic alcohol intoxication in a naturalistic clinical sample of men

BACKGROUND: Cortisol, the primary glucocorticoid in humans, is intimately involved in the regulation of such varied and critical biological processes as emotion, cognition, reward, immune functioning, and energy utilization. A persistent increase in cortisol concentration as a result of chronic intoxication could therefore result in alcohol-related disorders such as sleep disruption, cognitive deficits, diabetes, and mood disturbances. Although moderate levels of acute alcohol ingestion are reported to produce an increase in cortisol levels, it is uncertain whether cortisol remains persistently increased during long-term chronic intoxication. METHODS: Salivary cortisol and breath alcohol concentrations (BAC) were obtained on 73 subjects with primary alcohol dependence on initial presentation for treatment and 22 alcohol-dependent subjects participating in a residential treatment program. RESULTS: Both intoxicated alcohol-dependent subjects (n = 38) and nonintoxicated subjects in acute alcohol withdrawal (n = 30) demonstrated significantly increased salivary cortisol concentrations compared with abstinent subjects (n = 27; p < 0.001). Nonintoxicated subjects in acute withdrawal demonstrated significantly increased salivary cortisol concentrations compared with highly intoxicated subjects (BAC >100 mg/dl) but were similar to subjects with lower levels of intoxication (BAC, 10-100 mg/dl). CONCLUSIONS: Chronic alcohol-dependent subjects experience continuously increased concentrations of cortisol during both intoxication and withdrawal. Increased levels of cortisol during chronic intoxication seem to progressively increase with the onset of withdrawal. This suggests a daily cycle of hypercortisolemia during the active drinking phase, with further increases on the cessation of drinking and the emergence of withdrawal symptoms. Persistently increased levels of cortisol may extract a costly allostatic load, resulting in significant central nervous system and peripheral organ morbidity.     

Ethanol, acetaldehyde, acetate, and lactate levels after alcohol intake in white men and women: effect of 4-methylpyrazole

BACKGROUND: 4-Methylpyrazole (4-MP), a selective inhibitor of alcohol dehydrogenase (ADH), recently has been approved for clinical use in humans. The objective was to evaluate the use of 4-MP in human alcohol research and to study the effect of 4-MP on various parameters of alcohol metabolism during alcohol intoxication. METHODS: 4-MP (10-15 mg/kg orally) or placebo was given in double-blind fashion to 22 premenopausal women, 12 of whom were using oral contraceptives, and 13 men followed by intake of alcohol (0.5 g/kg orally) or placebo. RESULTS: A 30% to 40% decrease in the ethanol elimination rate was observed in the different groups during pretreatment with 4-MP. The alcohol-induced increase in plasma acetate was partially inhibited by 4-MP. A significant positive correlation was observed between the effect of 4-MP on the alcohol-induced lactate and acetate elevations. The acetaldehyde was nondetectable (<1 micromol/liter) in the peripheral venous blood during alcohol intoxication in both women and men. During alcohol intoxication, a decrease in breath acetaldehyde was found with 4-MP pretreatment in women but not in men. CONCLUSION: The alcohol-induced elevation in blood acetate level is caused, in part, by ADH-mediated ethanol oxidation. Although no evidence was found for measurable acetaldehyde levels in the peripheral venous blood during alcohol intoxication, the effect of 4-MP on breath acetaldehyde in women supports the view that ADH-mediated acetaldehyde elevations reflected in the airways, but too low to be detected in the peripheral venous blood, may occur in women during alcohol intoxication in the present experimental conditions.     

Melatonin (an antioxidant) does not ameliorate alcohol-induced Purkinje cell loss in the developing cerebellum

BACKGROUND: One popular mechanism proposed to account for alcohol-induced brain damage is the generation of free radicals after alcohol exposure. Therefore, it is reasonable to hypothesize that administration of an antioxidant should reduce the severity of alcohol-induced brain damage. Recently, melatonin has been shown to be an effective free-radical scavenger. In this study, the ability of melatonin to attenuate alcohol-induced cerebellar Purkinje cell loss in the cerebellar vermis and lobule I was assessed. METHODS: Sprague-Dawley rat pups were used in this study. These neonatal pups were exposed to alcohol (4.5 g/kg), melatonin (10 mg/kg), both alcohol and melatonin, or control vehicle via artificial-rearing methods from postnatal day (PD) 4 to PD 9. Alcohol, melatonin, or control vehicle was mixed with milk formula in 2 of the daily 12 feedings. Pups were killed 90 min after the beginning of the second alcohol feeding on PD 9. RESULTS: Alcohol significantly reduced the Purkinje cell numbers in the vermis and lobule I, with a higher percentage of cell loss in lobule I compared with the vermis. However, melatonin, per se, neither affected the Purkinje cell number nor diminished alcohol-induced Purkinje cell loss. CONCLUSIONS: Melatonin was not effective in attenuating alcohol-induced loss of Purkinje cells in our neonatal rat model system, even though such a dosage of melatonin is capable of reversing free radical-induced damage in other tissues.     

MK-801-induced locomotor activity in long-sleep x short-sleep recombinant inbred mouse strains: correlational analysis with low-dose ethanol and provisional quantitative trait loci

BACKGROUND: Low doses of the N-methyl-D-aspartate receptor (NMDAR) antagonist MK-801 (dizocilpine) or ethanol increase locomotor activity to a lesser extent in long-sleep (LS), than in short-sleep (SS), mice. LS mice also have fewer brain [3H]MK-801 binding sites than SS mice. In this study, LSXSS recombinant inbred (RI) mice were used to investigate whether different NMDAR densities contribute to differential MK-801 activation and whether common genes are involved in initial sensitivity to MK-801-and ethanol-induced activation. METHODS: Locomotor activity was measured for 90 min after saline or MK-801 injection. Quantitative autoradiographic analysis of [3H]MK-801 binding was used to measure densities of NMDARs in seven brain regions. The ethanol (1-2 g/kg) activation scores from Erwin and colleagues (1997) were used for correlational analysis, as was their method for quantitative trait loci (QTL) analysis. RESULTS: Both saline and MK-801 (0.3 mg/kg, given intraperitoneally) induced a continuum of locomotor responses across the LSXSS RI strains. There was a 4-fold range of MK-801 difference scores (MK-801 score-saline baseline), with the RI 9 and RI 4 strains representing low and high responders, respectively. Dose-response experiments with these two strains confirmed that 0.3 mg/kg MK-801 produced significant activation, similar to previous results with LS and SS mice. However, unlike previous LS/SS results, lower densities of NMDARs were not observed in the RI 9 than in the RI 4 mouse brains. No significant genetic correlations were observed between MK-801-induced and ethanol-induced responses in the LSXSS RI mice. Two provisional MK-801 activation QTLs were identified (p < 0.01) on chromosomes 11 and 19, neither in common with those mapped for ethanol activation. CONCLUSIONS: Different densities of brain NMDARs are unlikely to account for the differential activation of LSXSS RI mice by MK-801. Additionally, in the RI mice either separate sets of genes regulate low dose MK-801- and ethanol-induced locomotor responses or the overlapping subset of genes controlling these two behaviors is small (< or =10%).     

Melatonin increases cell proliferation in the dentate gyrus of maternally separated rats

Melatonin in mammals, produced by the pineal gland and elsewhere, has shown antioxidant and neuroprotective properties in neuronal cells. We investigated whether melatonin would increase newly born cells (cell proliferation) in the dentate gyrus of maternally separated rats. To examine the effect of melatonin on cell proliferation of the dentate gyrus in maternally separated rats, 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry was performed. Rat pups were separated from their mothers and socially isolated on postnatal day 14. Melatonin (10 mg/kg, i.p.) and BrdU (50 mg/kg, i.p.) were given to them for 7 days. The number of BrdU-positive cells was significantly increased in the dentate gyrus of maternally separated pups with melatonin administration (P < 0.001). In addition, the expression of glucocorticoid receptor was significantly decreased in the dentate gyrus compared with maternally separated pups not given melatonin (P < 0.001). This is the first report that melatonin increases cell proliferation in the dentate gyrus of maternally separated rats.     

Alcohol exposure during the brain growth spurt promotes hippocampal seizures, rapid kindling, and spreading depression

BACKGROUND: Epilepsy is a prominent sign of brain dysfunction and a cause of substantial disability in some children with fetal alcohol syndrome. The hippocampal formation is vulnerable to alcohol-induced pathologic changes and is the source of seizure activity in a variety of epileptic conditions. This study tests the hypothesis that developmental alcohol exposure facilitates epileptic activity and promotes kindling within hippocampal circuitry. METHODS: Rat pups received either a moderate dose (2.0 g/kg) or a high dose (3.75 g/kg) of alcohol via intragastric intubation over postnatal days 4 to 10. Intubated control and suckle control groups were also included. Upon reaching adulthood (postnatal days 85-100), the rats underwent electrophysiologic testing. A double-barrel potassium-sensitive microelectrode was placed into the right dentate gyrus stratum granulosum for the recording of extracellular field potential and extracellular potassium concentration. Stimuli were delivered via an electrode positioned in the CA3 subregion of the left hippocampus. To assess whether alcohol promotes hippocampal seizures and rapid kindling, the parameters of maximal dentate activation (MDA) were measured before, during, and after a series of stimulation-induced seizures. RESULTS: Developmental exposure to the high dose of alcohol permanently altered several parameters of MDA. Time to onset of MDA and stimulus threshold for afterdischarge production were both decreased, whereas the duration of the afterdischarge was increased. Although the moderate alcohol dose reduced time to onset of MDA, it did not affect any other MDA parameters. Over the course of the repeated induced seizures, spreading depression occurred more often and with fewer stimuli in the high-dose alcohol group than in any other group. The series of repeated electrographic seizures induced rapid kindling in all of the treatment groups. However, the kindling effect was enhanced in a dose-response manner by the previous alcohol exposures. CONCLUSIONS: These findings demonstrate that exposure to alcohol during brain development can permanently alter the physiology of the hippocampal formation, thus promoting epileptic activity, enhancing kindling, and facilitating spreading depression. The relative roles of alcohol intoxication and withdrawal in these abnormal physiologic responses remain unknown.     

From the Cover: Long-lasting reduction in hippocampal neurogenesis by alcohol consumption in adolescent nonhuman primates

Binge alcohol consumption in adolescents is increasing, and studies in animal models show that adolescence is a period of high vulnerability to brain insults. The purpose of the present study was to determine the deleterious effects of binge alcohol on hippocampal neurogenesis in adolescent nonhuman primates. Heavy binge alcohol consumption over 11 mo dramatically and persistently decreased hippocampal proliferation and neurogenesis. Combinatorial analysis revealed distinct, actively dividing hippocampal neural progenitor cell types in the subgranular zone of the dentate gyrus that were in transition from stem-like radial glia-like cells (type 1) to immature transiently amplifying neuroblasts (type 2a, type 2b, and type 3), suggesting the evolutionary conservation of milestones of neuronal development in macaque monkeys. Alcohol significantly decreased the number of actively dividing type 1, 2a, and 2b cell types without significantly altering the early neuronal type 3 cells, suggesting that alcohol interferes with the division and migration of hippocampal preneuronal progenitors. Furthermore, the lasting alcohol-induced reduction in hippocampal neurogenesis paralleled an increase in neural degeneration mediated by nonapoptotic pathways. Altogether, these results demonstrate that the hippocampal neurogenic niche during adolescence is highly vulnerable to alcohol and that alcohol decreases neuronal turnover in adolescent nonhuman primate hippocampus by altering the ongoing process of neuronal development. This lasting effect, observed 2 mo after alcohol discontinuation, may underlie the deficits in hippocampus-associated cognitive tasks that are observed in alcoholics.