Effects Of Chronic Ethanol Treatment Research Articles

Sex differences in cholinergic circuits and behavioral disruptions following chronic ethanol exposure with and without thiamine deficiency.

Few studies have investigated differences in the vulnerabilities of males and females to alcohol use disorder and alcohol-related brain damage (ARBD). According to epidemiological and clinical findings, females appear to be more sensitive to the effects of alcohol and thiamine deficiency and have a worse prognosis in recovery from neurocognitive deficits compared with males. This study aimed to characterize the effects of chronic ethanol (EtOH) toxicity and thiamine deficiency across the sexes using rodent models. Male and female Sprague Dawley rats were assigned to chronic forced EtOH treatment (CET), pyrithiamine-induced thiamine deficiency (PTD), combined CET-PTD, or pair-fed (PF) control treatment conditions. Following treatments, spatial working memory was assessed during a spontaneous alternation task while measuring acetylcholine (ACh) in the prefrontal cortex (PFC) and the hippocampus (HPC). The animals also underwent an operant-based attentional set-shifting task (ASST) for the analysis of behavioral flexibility. Female and male rats did not differ in terms of EtOH consumption; however, the CET and CET-PTD-treated female rats had lower BECs than male rats. Compared with the PF group, the CET, PTD, and CET-PTD groups exhibited spatial working memory impairments with corresponding reductions in ACh efflux in the PFC and HPC. The ASST revealed that CET-PTD-treated males and females displayed impairments marked by increased latency to make decisions. Thalamic shrinkage was prominent only in the CET-PTD and PTD treatment conditions, but no sex-specific effects were observed. Although the CET and CET-PTD-treated females had lower BECs than the males, they demonstrated similar cognitive impairments. These results provide evidence that female rats experience behavioral and neurochemical disruptions at lower levels of alcohol exposure than males and that chronic EtOH and thiamine deficiencies produce a unique behavioral profile.

Chronic Ethanol Consumption and Thiamine Deficiency Modulate β-Amyloid Peptide Level and Oxidative Stress in the Brain.

Aims The effects of chronic ethanol (EtOH) consumption, associated or not with thiamine deficiency (TD), on β-amyloid peptide (Aβ) level and oxidative stress in the brain were studied in male C57BL/6 mice. Methods Mice were prepared by feeding with an EtOH liquid diet, thiamine-depleted liquid diet and a thiamine-depleted EtOH liquid diet for 7 weeks. Biochemical parameters were measured by corresponding commercial kits. Results EtOH consumption or TD induced a significant decrease in the thiamine level, but induced increased in the β-amyloid peptide 1–42 and β-amyloid peptide 1–40 (Aβ1–40) levels. EtOH consumption led to a significant increase in the malondialdehyde (MDA) and nitric oxide (NO) levels, total nitric oxide synthase (NOS) activities and inducible nitric oxide synthase (iNOS) activities, but a significant decrease in superoxide dismutase (SOD) and glutathione peroxidase activities. TD significantly elevated the MDA content and total NOS and iNOS activities but lowered SOD activity. Aβ1–40 overproduction, the change in the NO level, and SOD activity in the brain induced by chronic EtOH treatment associated with TD were greater than that induced by EtOH or TD alone. Conclusion Findings from this report suggested that chronic EtOH consumption could induce TD, excess Aβ production and oxidative damage, and the association with TD should have more severe effects on the brain. Short summary Chronic EtOH consumption or thiamine deficiency (TD) treatment could reduce the thiamine level, induce β-amyloid peptide (Aβ) overproduction and oxidative stress in the brain. When associated with TD, EtOH consumption caused Aβ overproduction and oxidative damage more serious.

Effect of chronic ethanol treatment on μ-opioid receptor function, interacting proteins and morphine-induced place preference

Both the acute and chronic consumption of ethanol have been reported to modify several molecular events in the central nervous system, and the endogenous μ-opioid receptor system is involved in the reinforcing/rewarding effects of ethanol. The present study was designed to clarify the effects of chronic ethanol treatment on cellular processes involving μ-opioid receptor and the development of morphine-induced rewarding effects. Male C57BL/6J mice were continuously treated with a liquid diet containing 3.0 w/v ethanol. The direct involvement of μ-opioid receptor functions in the activation of G-proteins and changes in protein levels in the lower midbrain of mice after chronic treatment with ethanol were investigated by a [(35)S] GTPγS binding assay and Western blotting, respectively. The rewarding effects of morphine (5 mg/kg) under treatment with ethanol were measured by the conditioned place preference paradigm. The function of μ-opioid receptor was increased by treatment with ethanol in the lower midbrain using [(35)S] GTPγS binding assay. Furthermore, the GRK2 protein level was significantly increased by treatment with ethanol. Chronic treatment with ethanol enhanced the rewarding effects of morphine. On the other hand, this enhancement of the rewarding effects of morphine by ethanol treatment was significantly inhibited by the GRK2 inhibitor β-adrenergic receptor kinase 1 inhibitor. The present study demonstrated that chronic treatment with ethanol enhanced the rewarding effects of morphine by up-regulating functional changes in μ-opioid receptor, mediated by GRK2.

Chronic ethanol feeding enhances miR-21 induction during liver regeneration while inhibiting proliferation in rats

Liver regeneration is an important repair response to liver injury. Chronic ethanol consumption inhibits and delays liver regeneration in experimental animals. We studied the effects of chronic ethanol treatment on messenger RNA (mRNA) and microRNA (miRNA) expression profiles during the first 24 h after two-thirds partial hepatectomy (PHx) and found an increase in hepatic miR-21 expression in both ethanol-fed and pair-fed control rats after PHx. We demonstrate that the increase of miR-21 expression during liver regeneration is more robust in ethanol-fed rats. Peak miR-21 expression occurs at 24 h after PHx in both ethanol-fed and control rats, corresponding to the peak of hepatocyte S phase in control rats, but not in ethanol-exposed livers in which cell cycle is delayed. The induction of miR-21 24 h after PHx in control rats is not greater than the increase in expression of miR-21 due to sham surgery. However, in the ethanol-fed rat, miR-21 is induced to a greater extent by PHx than by sham surgery. To elucidate the implications of increased miR-21 expression during liver regeneration, we employed unbiased global target analysis using gene expression data compiled by our group. Our analyses suggest that miR-21 may play a greater role in regulating gene expression during regeneration in the ethanol-fed rat than in the control rat. Our analysis of potential targets of miR-21 suggests that miR-21 affects a broad range of target processes and may have a widespread regulatory role under conditions of suppressed liver regeneration in ethanol-treated animals.

Learning not to be impulsive: disruption by experience of alcohol withdrawal

There is extensive evidence that alcoholism and impulsivity are related, but the direction of causality is unclear. The aim of the present investigation was to study the effects of chronic ethanol treatment and withdrawal in measures of attention and impulse control in the five-choice serial reaction time task (5CSRTT) in mice. C57BL/6J mice were trained in the 5CSRTT and then tested in a variable inter-trial interval (vITI) session, which promotes the emergence of premature responses, a measure of poor inhibitory control. Following chronic ethanol treatment, mice were tested in additional vITI sessions-in experiment 1, at 1, 7 and 14days post-withdrawal, and in experiment 2, at 14, 28, 42 and 56days post-withdrawal. Control animals showed a reduction in premature responding with experience of the vITI schedule. Compared to controls, previous ethanol treatment did not affect attention or impulsivity on first experience of the vITI procedure. Ethanol-treated animals showed sustained increased premature responding over sessions. This effect of ethanol treatment was not apparent in experiment 2, in which first exposure to the vITI schedule was delayed for 2weeks following ethanol treatment. Chronic ethanol treatment impaired the ability to learn to modify behaviour in order to gain access to reinforcement more frequently. This effect was related to the time since withdrawal.

Lysophosphatidic acid rescues RhoA activation and phosphoinositides levels in astrocytes exposed to ethanol

Long-term ethanol treatment substantially impairs glycosylation and membrane trafficking in primary cultures of rat astrocytes. Our previous studies indicated that these effects were attributable to a primary alteration in the dynamics and organization of the actin cytoskeleton, although the molecular mechanism(s) remains to be elucidated. As small Rho GTPases and phosphoinositides are involved in the actin cytoskeleton organization, we now explore the effects of chronic ethanol treatment on these pathways. We show that chronic ethanol treatment of rat astrocytes specifically reduced endogenous levels of active RhoA as a result of the increase of in the RhoGAP activity. Furthermore, ethanol-treated astrocytes showed reduced phosphoinositides levels. When lysophosphatidic acid was added to ethanol-treated astrocytes, it rapidly reverted actin cytoskeleton reorganization and raised active RhoA levels and phosphoinositides content to those observed in untreated astrocytes. Overall, our results indicate that the harmful effects of chronic exposure to ethanol on a variety of actin dynamics-associated cellular events are primarily because of alterations of activated RhoA and phosphoinositides pools.

Effects of chronic ethanol administration on brain protein levels: A proteomic investigation using 2-D DIGE system

The effects of chronic ethanol treatment on the brain proteome were investigated in the long-fin striped strain of zebrafish Danio rerio. Prolonged exposure to 0.5% (v/v) ethanol resulted in the development of tolerance to the ethanol-induced disruption of normal swimming behavior. This behavioral tolerance was manifested after two weeks of continuous treatment and was maintained for an additional three weeks. After four weeks of ethanol treatment, zebrafish brains were divided into 40,000 g supernatant and pellet fractions, and an Ettan 2-D fluorescence difference gel electrophoresis (DIGE) system was used to detect ethanol-induced alterations in the level of protein expression. Protein identification was carried out using matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry and the Mascot and ProFound search engines. In the present study, we have identified some novel protein targets as well as substantiated some putative previous targets of chronic ethanol exposure.

Effects of chronic ethanol treatment on glial fibrillary acidic protein expression in adult rat optic nerve: an immunocytochemical study

Glial fibrillary acidic protein (GFAP) is used as a marker of astrocyte response to various central nervous system injuries. In the present study, the effects of chronic ethanol administration on GFAP immunoreactivity were evaluated in astrocytes of the adult optic nerve head. The results demonstrated that ethanol exposure significantly and dramatically increases GFAP immunoreactivity and the number of immunoreactive astrocytes (p<0.001). In addition, GFAP immunoreactive cells in the optic nerve showed extensive hypertrophy (p<0.001).

Effects of chronic ethanol treatment on monoamine levels in rat hippocampus and striatum

We studied the effects of ethanol on concentrations of noradrenaline (NE), dopamine (DA) and serotonin (5-HT) and their metabolites in rat hippocampus and striatum. Ethanol (2 or 4 g/kg, po, from a 20% aqueous solution) was administered daily to male Wistar rats (4-13 per group) for 30 days and animals were sacrificed 30 min or 48 h after the last administration. Monoamines were measured by HPLC and considered significant at P < 0.05. A 47% increase in 5-HT levels was observed in the hippocampus with 4 g/kg ethanol in the 30-min protocol. Ethanol (2 and 4 g/kg) decreased DA (2114.5 +/- 126.4 and 1785.1 +/- 234.2 ng/g wet tissue, respectively) and 3,4-dihydroxyphenylacetic acid (DOPAC, 1477.6 +/- 132.1 and 1218.8 +/- 271.7 ng/g wet tissue, respectively) levels, while the higher dose also decreased NE (159.8 +/- 13.5), 5-HT (228.0 +/- 46.8) and 5-hydroxy-3-indoleacetic acid (5-HIAA, 304.4 +/- 37.2 ng/g wet tissue), in the striatum after a 48-h withdrawal as compared to controls (DA: 3063.9 +/- 321.3; DOPAC: 2379.6 +/- 256.0; NE: 292.8 +/- 50.2; 5-HT: 412.4 +/- 36.2; 5-HIAA: 703.9 +/- 61.4 ng/g wet tissue). In the 30-min protocol, ethanol (2 or 4 g/kg) decreased striatal NE (66 and 70%) and DA (50 and 36%) levels. On the other hand, increases were seen in 5-HIAA (146 and 153%) and 5-HT (59 and 86%) levels. Ethanol (2 g/kg, po) increased the homovanillic acid (HVA)/DA ratio (129%) in the striatum in the 30-min protocol, while at the higher dose it increased the HVA/DA ratio in the 48-h protocol (61%). These results indicate alterations in monoamines, mainly in the striatum, after chronic ethanol, which are influenced by dose and by the length of time after the last drug administration.

Chronic ethanol treatment reduces the magnitude of hippocampal LTD in the adult rat.

Human alcoholics and animals that have received chronic ethanol treatment (CET) display memory deficits. Previous work in our laboratory has shown that CET produces damage to the hippocampus and a reduction in the magnitude of hippocampal long-term synaptic potentiation. In the present report we examined the effects of CET on hippocampal long-term depression (LTD). We used in vitro hippocampal slices to examine LTD after rats received 38-41 weeks of paired feeding on liquid diets containing ethanol or isocaloric sucrose. Stimulation delivered through electrodes in the CA3-CA1 Schaffer collateral pathway activated synaptic population responses in CA1. LTD of CA1 stratum radiatum evoked field potential slope was not induced by 900 single pulses at 1 Hz, but was elicited by 900 pulse pairs separated by 50 or 200 msec delivered at 1 Hz (pLFS50, pLFS200). LTD evoked by pLFS200, but not by pLFS50, was significantly reduced in slices from ethanol-treated rats. The N-methyl D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonopentanoic acid (AP5) (50 micro M) blocked LTD induced by pLFS50 and pLFS200 equally, but the L-type calcium channel blocker nimodipine (10 micro M) had no effect on either type of LTD. Thus, direct effects on these channels cannot explain how CET selectively reduces the magnitude of pLFS200 LTD. Finally, we describe a novel and robust LTD of the presynaptic afferent volley that is resistant to CET, NMDAR antagonists, GABA-A receptor blockade, and blockade of L-type calcium channels.

Effects of chronic ethanol treatment on the angiotensin II–mediated p42/p44 mitogen-activated protein kinase and phosphorylase a activation in rat hepatocytes

We have demonstrated previously that 24 h of ethanol treatment potentiates angiotensin II (ANG II)–stimulated p42/p44 mitogen-activated protein kinase (MAPK) activity in hepatocytes. This potentiation of p42/p44 MAPK by ethanol exhibited agonist selectivity. To compare the effects of acute (24 h) versus chronic (6 weeks) ethanol treatment, ANG II-induced intracellular signaling was examined in (1) rat hepatocytes treated with ethanol for 24 h and (2) hepatocytes obtained from rats fed ethanol for 6 weeks. In hepatocytes obtained from rats fed ethanol for 6 weeks, ANG II-stimulated phosphorylase a was reduced, and this activity was calcium dependent and p42/p44 MAPK independent. Surprisingly, ANG II-stimulated p42/p44 MAPK activation was not affected in hepatocytes obtained from rats fed ethanol chronically (6 weeks). However, chronic (6 weeks) ethanol treatment decreased ethanol potentiation of p42/p44 MAPK by about 56.3% ± 3.6% for p42 MAPK and 61.3% ± 11.7% for p44 MAPK. Furthermore, ethanol had no effect on the expression of angiotensinogen and c- myc mRNA in hepatocytes. A decrease in ANG II-activated phosphorylase a, but not in p42/p44 MAPK activation, after chronic (6 weeks) ethanol treatment leads to the conclusion that they may not be dependent on each other.

Differential Effects of Chronic Ethanol Treatment onN-Methyl-d-aspartate R1 Splice Variants in Fetal Cortical Neurons

Functional N-methyl-D-aspartate receptors consisting of NR1 and NR2 subunits are an important site of action of ethanol. Chronic ethanol treatment increases the NR1 polypeptide levels in vivo and in vitro. Chronic ethanol treatment in vitro does not significantly alter the NR1 mRNA levels, even though under similar culture conditions ethanol (50 mm, 5 days) enhances the half-life of NR1 mRNA in fetal cortical neurons. To address this phenomenon, we determined by reverse transcription-polymerase chain reaction and Western blotting whether ethanol (50 mm, 5 days) has a splice variant-specific effect on the expression of the NR1 subunit in mouse fetal cortical neurons. This report analyzes for the first time the distribution of all NR1 splice variants in these neurons. Our data indicate the presence of NR1-3a,b and NR1-4a,b splice variants in cortical neurons. Chronic ethanol treatment significantly decreased the mRNA levels of exon 5-containing NR1 splice variants (NR1-3b and NR1-4b) (-E5/+E5 = 4.6 in untreated neurons and 6.1 in ethanol-treated neurons) and had no effect on the mRNA levels of NR1-3 (+E21/-E22) and NR1-4 (-E21/-E22) splice variants. At the polypeptide level, chronic ethanol treatment significantly reduced exon 5-containing splice variants (NR1-3b and NR1-4b). However, ethanol (50 mm, 5 days) induced a significant increase in polypeptide levels of NR1-4 (-E21/-E22), without any effect on NR1-3 (+E21/-E22) polypeptide levels. These results demonstrate that chronic ethanol treatment has a selective effect on the expression of NR1 splice variants at both the mRNA and polypeptide levels in mouse fetal cortical neurons.

Chronic exposure to ethanol alters GABA(A) receptor-mediated responses of layer II pyramidal cells in adult rat piriform cortex.

This study examined the effect of chronic exposure to ethanol on gamma-aminobutyric acid type-A (GABA(A)) receptor-mediated responses of layer II pyramidal neurons of the piriform cortex. Slices containing the piriform cortex were derived from pair-fed adult rats maintained on ethanol-supplemented or control liquid diet for 30 days. Responses of identified layer II pyramidal neurons to exogenously applied GABA were monitored by whole-cell patch-clamp recording. Chronic exposure to ethanol resulted in a rightward shift in the EC(50) of GABA and a decrease in the amplitude of maximal GABA response. GABA-induced responses were modulated by acutely applied ethanol (10-100 mM) in both chronic ethanol-treated and control groups. No significant difference was found in the average change in GABA response, suggesting that tolerance to acute ethanol exposure did not develop. When the modulatory responses of individual cells were classified and grouped as either being attenuating, potentiating, or having no effect, the incidence of potentiation in the ethanol-treated group was significantly higher. Consistent with the absence of tolerance to acute ethanol, cross-tolerance to diazepam was not observed following 30 days of treatment with ethanol. These results are discussed in light of regionally specific effects of chronic ethanol treatment on GABA(A) receptor-mediated responses of layer II piriform cortical neurons.

Effect of Chronic Ethanol Exposure on Inositol Trisphosphate Receptors in WB Rat Liver Epithelial Cells

Background: Enhanced agonist-induced Ca2+ release has been reported in hepatocytes isolated from ethanol-fed rats. Because myo-inositol 1,4,5-trisphosphate receptors (IP3Rs) are involved in the mobilization of Ca2+, we examined the effects of chronic ethanol treatment on IP3R function and levels of IP3R protein by using WB rat liver epithelial cells. Methods: WB cells were treated with ethanol (50–150 mM) for 24 to 48 hr and were loaded with Fura-2 to measure agonist-induced Ca2+ mobilization or saponin permeabilized to measure myo-inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ release. IP3 levels were measured in [3H]-inositol labeled cells. Levels of IP3R protein were quantitated by immunoblotting with antibodies to IP3R isoforms. Lysosomal and proteasomal peptidase activities were assayed in cytosol and membrane fractions using specific fluorogenic peptide substrates. Results: Ethanol treatment enhanced Ca2+ mobilization in response to angiotensin II, vasopressin, and bradykinin. This effect was not due to an increased production of IP3. Chronic ethanol treatment stimulated the mobilization of Ca2+ from saponin-permeabilized cells in response to subsaturating doses of IP3 and increased the basal levels of both type I and type III IP3Rs by 1.8-fold and 1.6-fold, respectively. Ethanol treatment did not prevent angiotensin II-induced IP3R down-regulation or alter lysosomal cathepsin B activity or the trypsin-like and peptidylglutamyl peptidase activities of the proteasome. However, chronic ethanol exposure resulted in a 60% and 41% inhibition of the chymotrypsin-like activity of the proteasome in cytosol and microsomal membranes, respectively. Conclusion : We propose that the enhanced agonist-mediated Ca2+ mobilization observed in chronic ethanol-treated WB liver epithelial cells results from increased IP3R expression caused by an inhibition of IP3R degradation pathways by ethanol.

Effect of Chronic Ethanol Exposure on Inositol Trisphosphate Receptors in WB Rat Liver Epithelial Cells

Enhanced agonist-induced Ca2+ release has been reported in hepatocytes isolated from ethanol-fed rats. Because myo-inositol 1,4,5-trisphosphate receptors (IP3Rs) are involved in the mobilization of Ca2+, we examined the effects of chronic ethanol treatment on IP3R function and levels of IP3R protein by using WB rat liver epithelial cells. WB cells were treated with ethanol (50-150 mM) for 24 to 48 hr and were loaded with Fura-2 to measure agonist-induced Ca2+ mobilization or saponin permeabilized to measure myo-inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ release. IP3 levels were measured in [3H]-inositol labeled cells. Levels of IP3R protein were quantitated by immunoblotting with antibodies to IP3R isoforms. Lysosomal and proteasomal peptidase activities were assayed in cytosol and membrane fractions using specific fluorogenic peptide substrates. Ethanol treatment enhanced Ca2+ mobilization in response to angiotensin II, vasopressin, and bradykinin. This effect was not due to an increased production of IP3. Chronic ethanol treatment stimulated the mobilization of Ca2+ from saponin-permeabilized cells in response to subsaturating doses of IP3 and increased the basal levels of both type I and type III IP3Rs by 1.8-fold and 1.6-fold, respectively. Ethanol treatment did not prevent angiotensin II-induced IP3R down-regulation or alter lysosomal cathepsin B activity or the trypsin-like and peptidylglutamyl peptidase activities of the proteasome. However, chronic ethanol exposure resulted in a 60% and 41% inhibition of the chymotrypsin-like activity of the proteasome in cytosol and microsomal membranes, respectively. We propose that the enhanced agonist-mediated Ca2+ mobilization observed in chronic ethanol-treated WB liver epithelial cells results from increased IP3R expression caused by an inhibition of IP3R degradation pathways by ethanol.

Chronic intermittent ethanol exposure alters CA1 synaptic transmission in rat hippocampal slices

We investigated the neuroadaptive changes in synaptic transmission in the CA1 region of the hippocampus as a result of chronic intermittent ethanol exposure. Male Wistar rats were exposed daily (14 h) to ethanol vapors (blood alcohol levels=150–200 mg%) for 12–14 days, and synaptic field potentials elicited by Schaffer collateral stimulation were compared in hippocampal slices from control and chronic ethanol-treated rats. Excitatory postsynaptic responses of slices were recorded under three conditions: (i) normal physiological saline; (ii) continued presence of 33 mM (150 mg%) ethanol (chronic ethanol-treated rats only); (iii) acute exposure to 33 mM ethanol. When recorded in ethanol-free physiological saline, the mean amplitude of the dendritic synaptic potential and the somatic population spike were significantly smaller in slices from chronic ethanol-treated rats compared to slices from control rats. Under conditions of continuous ethanol exposure, somatic and dendritic synaptic responses of slices taken from chronic ethanol-treated rats were further depressed, suggesting that neural pathways in area CA1 remained sensitive to ethanol. Acute application of ethanol led to a more pronounced reduction of the mean somatic population spike amplitude in slices from chronic ethanol-treated rats than in slices from control rats. However, dendritic synaptic responses were unaffected by acute ethanol in slices from both control and chronic ethanol-treated rats. In addition, we examined the involvement of presynaptic mechanisms in the effects of chronic intermittent ethanol using paired-pulse protocols. When recorded in the continued presence of ethanol, slices from chronic ethanol-treated rats exhibited a significant reduction in paired-pulse facilitation of the dendritic synaptic response compared to slices from control rats, indicating a presynaptic component to the neuroadaptive effects of chronic intermittent ethanol exposure. Conversely, acute ethanol exposure resulted in an enhancement of paired-pulse facilitation of the dendritic synaptic response, an effect that was similar in slices from both control and chronic ethanol-treated rats. Paired-pulse facilitation of the somatic population spike amplitude was not altered by chronic ethanol treatment. However, acute ethanol exposure significantly enhanced paired-pulse facilitation of the somatic population spike in slices from chronic ethanol-treated rats. This effect of acute ethanol was not observed in slices from control rats. Paired-pulse inhibition was not significantly altered in slices from chronic ethanol-treated rats, suggesting that GABAergic inhibitory mechanisms were not involved in the neuroadaptive effects of chronic intermittent ethanol exposure. We suggest that chronic intermittent ethanol exposure can induce multiple neuroadaptive changes in synaptic transmission of CA1 pyramidal neurons that are detectable at both the pre- and postsynaptic levels. Alterations in paired-pulse facilitation indicate presynaptic changes involving the release of the excitatory neurotransmitter glutamate, whereas changes in dendritic synaptic responses suggest postsynaptic changes in the responsiveness of neurons to synaptic input. Moreover, differential effects of chronic ethanol treatment on synaptic responses recorded in the dendrites versus the somatic region implicate additional effects of ethanol on somatically located mechanisms of CA1 pyramidal neurons. Furthermore, we suggest that complete tolerance to ethanol does not occur in the CA1 region of the hippocampus following chronic intermittent ethanol exposure.

Prolonged effects of chronic ethanol treatment on responses to repeated nicotine administration: interactions with environmental cues

The most common combination of dependence on two drugs occurs with alcohol and nicotine, but little is known of the way in which these drugs interact in the brain. This study investigated the effects in mice of prolonged consumption of alcohol, by liquid diet, on the actions of nicotine on locomotor activity, and the influence of environmental cues on these effects. Administration of nicotine after chronic alcohol intake did not show any significant changes on first administration, but after 28 days of daily nicotine injections, nicotine produced significant locomotor stimulation and increased rearing activity in the mice which had previously received the alcohol diet, compared with the activity of animals that received the control diet. However, significantly increased locomotor activity was also seen, after the repeated nicotine administration, immediately prior to the nicotine injection, only in the mice that had previously consumed alcohol. Examination of the influence of the environment in which the activity was tested demonstrated that the effect on activity prior to injections was seen only if measurement was made in a test environment that was familiar to the animals. The results demonstrate an interaction between chronic alcohol consumption and the effects of environment on the actions of nicotine, that may have relevance to the consumption of these drugs in humans.

Effects of ethanol on the expression and secretion of bile salt-dependent lipase by pancreatic AR4-2J cells

The mechanisms by which ethanol administration alters pancreatic function are unknown. We have evaluated the effects of chronic ethanol treatment on secretion of a digestive enzyme: the bile salt-dependent lipase (BSDL), by the rat pancreatic cell line AR4-2J (as a model). We report that ethanol (50–300 mM) in culture medium induced a rise, in secreted and intracellular BSDL, that was a function of the duration of treatment and of the ethanol concentration. This effect was not abolished by pyrazole, which suggests a direct effect of ethanol. We have further established that the increase of BSDL activity was due to an enhanced biosynthesis of the enzyme consecutive to a major steady-state level of mRNA encoding BSDL. Also, the subcellular localization showed a specific accumulation of BSDL in the cytosolic fraction of cells chronically treated with ethanol. Given the enzymatic properties of BSDL, all these data could have some physiological consequences regarding the digestive function, plasma lipid metabolism and intracellular cholesterol homeostasis.

Chronic Ethanol Treatment Leads to Increased Ornithine Decarboxylase Activity

Recent research has focused on the N-methyl-D-aspartate receptor system as a major site of ethanol action in the brain and specifically on compensatory changes in the expression of the polyamine-sensitive NR2B subunit. Therefore, we examined the effects of chronic ethanol treatment on polyamine homeostasis in the rat brain. Wistar rats were made dependent by ethanol vapor inhalation. This caused a rise in hippocampal ornithine decarboxylase (ODC) activity that was correlated with the appearance of physiological dependence. ODC activity returned to control levels within 3 days of ethanol withdrawal. Enzyme activity also increased in the cerebral cortex, striatum, and cerebellum of the ethanol-dependent rats. The concentration of the polyamines (putrescine, spermidine, and spermine) in the hippocampus was increased in ethanol-dependent rats. Injection of the ODC inhibitor, alpha-difluoromethylornithine (500 mg/kg) at the onset of withdrawal resulted in a significant reduction in the severity of withdrawal behaviors. The level of ODC activity and the severity of withdrawal behaviors were positively correlated. Perturbed polyamine homeostasis may represent an important molecular component in the initiation of ethanol withdrawal behaviors in the ethanol-dependent rat.

Chronic Ethanol Treatment Leads to Increased Ornithine Decarboxylase Activity: Implications for a Role of Polyamines in Ethanol Dependence and Withdrawal

Recent research has focused on the N-methyl-D-aspartate receptor system as a major site of ethanol action in the brain and specifically on compensatory changes in the expression of the polyamine-sensitive NR2B subunit. Therefore, we examined the effects of chronic ethanol treatment on polyamine homeostasis in the rat brain. Wistar rats were made dependent by ethanol vapor inhalation. This caused a rise in hippocampal ornithine decarboxylase (ODC) activity that was correlated with the appearance of physiological dependence. ODC activity returned to control levels within 3 days of ethanol withdrawal. Enzyme activity also increased in the cerebral cortex, striatum, and cerebellum of the ethanol-dependent rats. The concentration of the polyamines (putrescine, spermidine, and spermine) in the hippocampus was increased in ethanol-dependent rats. Injection of the ODC inhibitor, alpha-difluoromethylornithine (500 mg/kg) at the onset of withdrawal resulted in a significant reduction in the severity of withdrawal behaviors. The level of ODC activity and the severity of withdrawal behaviors were positively correlated. Perturbed polyamine homeostasis may represent an important molecular component in the initiation of ethanol withdrawal behaviors in the ethanol-dependent rat.