Changes in dopamine transporter and c-Fos expression in the nucleus accumbens of alcohol-tolerant rats

BACKGROUND: We have shown that neurochemical functions of 5-HT3 receptors in regulating dopamine (DA) release in the nucleus accumbens (ACC) after alcohol exposure compensate for the dysfunction of serotonergic activity to restore the original properties in processing alcohol tolerance, and that the development of alcohol dependence may be mediated by ACC 5-HT3 receptors. In the present study, the effects of chronic alcohol consumption on the functions of the dopamine transporter (DAT) and the expression of c-Fos proteins were investigated using in vivo brain microdialysis and immunocytochemistry. METHODS: Perfusion of cocaine and 1-(2-Bis-(4-fluorophenyl) methoxy) ethyl)-4-(3-phenylpropyl) piperizine (GBR 12909) through the microdialysis probe membrane increased the extracellular levels of DA in ACC of alcohol-treated rats that had developed alcohol tolerance by drinking 10% EtOH for 30 days. RESULTS: The magnitudes of DA reuptake or DAT inhibitors, cocaine, and GBR 12909 that induced DA availability in the ACC were significantly higher in alcohol-treated rats than in controls. When compared with control rats, the alcohol-treated rats exhibited higher levels of DA and its metabolite, DOPAC, in the ACC. Increased expression of the c-Fos-like protein was found in the ACC of alcohol-treated rats. These results show that (1) chronic alcohol consumption desensitizes or decreases the DAT of DA terminals in the ACC and that (2) EtOH causes cellular hyperexcitability of ACC dopaminergic neurons with increased Fos expression during alcohol tolerance. CONCLUSION: The findings suggested that an abnormality of the dopaminergic neurons in the ACC that are involved with DAT dysfunction is associated with the development of alcohol tolerance.     

Ethanol Enhances the Release of Dopamine and Serotonin in the Nucleus Accumbens of HAD and LAD Lines of Rats

The effects of intraperitoneal administration of ethanol, 0.5, 1.0, and 2.0 g/kg body weight, on the extracellular concentrations of dopamine (DA), serotonin (5-HT), and their major metabolites were studied in the nucleus accumbens (ACC) of alcohol-naive, selectively bred high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) lines of rats using the technique of microdialysis. In both lines, the extracellular levels of DA were increased following the injection of 1.0 and 2.0 g of ethanol/kg body weight while only the 2.0-g/kg dose elevated the concentration of 5-HT. None of the ethanol doses altered the extracellular levels of the major metabolites of DA and 5-HT. Dose-response curves for DA and 5-HT release indicated no marked difference in the sensitivity to ethanol between the lines. Local perfusion with 60 mM K+ through the microdialysis probe markedly enhanced the release of DA and 5-HT in the ACC of both lines; there was a small difference between the lines in the amounts of DA, but not 5-HT, released by K(+)-stimulation. Overall, the results indicate that (1) the ACC DA system is more sensitive than the ACC 5-HT system to intraperitoneal ethanol administration in both lines and (2) there is no evidence for a relationship between alcohol preference and sensitivity of the ACC DA and 5-HT systems to acute intraperitoneal ethanol administration.     

Treating Neonatal Rats With 6-Hydroxydopamine Induced an Increase in Voluntary Alcohol Consumption

Brain dopamine (DA) and serotonin (5-HT) neurotransmission have been implicated in the mediation of alcohol-seeking behavior. We examined the effects of treatment of neonatal rats (3 days after birth) with the neurotoxin 6-hydroxydopamine (6-OHDA; 100 μg/10 μl, intracerebroventricularly) on the relationship between the levels of neurotransmitters and alcohol drinking behavior at the age of 14 weeks. 6-OHDA treatment reduced the levels of DA and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in the nucleus accumbens (ACC), frontal cortex, striatum (STR), tegmentum/substantia nigra, and dorsal raphe nucleus. 5-HT levels in the ACC and STR were increased in the 6-OHDA-treated rats. 6-OHDA-treated rats showed increased alcohol consumption. There was a significant change in the ratio of [5-hydroxyindoleacetic acid]/[5-HT] in the ACC and STR of the treated rats, but no difference in the ratio of [DOPAC]/[DA] between the sham-operated controls and treated rats. 6-OHDA-treated rats had dopaminergic dysfunction in the five brain regions related to the reward system, in part, and a decrease in 5-HT turnover, including the accumulation of 5-HT in the ACC and STR. Furthermore, basal extracellular releases of DA and 5-HT of the ACC were significantly lower in the 6-OHDA-treated rats, compared with the controls. It was suggested that alcohol seeking behavior is associated with the alterations of dopaminergic neurons and the release of 5-HT in the mesocorticolimbic system.     

Effects of Chronic Ethanol Consumption and Aging on 5-HT2A Receptors and 5-HT Reuptake Sites

The serotonergic system in brain is adversely affected by both aging and chronic ethanol consumption. The present study examined the combined effects of aging and chronic ethanol consumption on two components of the serotonergic system. Serotonin (5-HT) reuptake sites and 5-HT_2A receptors were quantitated in brain areas of 5-, 14-, and 24-month-old male Fischer 344 rats that were pair-fed a control or 6.6% (v/v) ethanol-containing liquid diet on a chronic basis. The regions examined include those containing the cell bodies and projections of serotonergic neurons. These experiments demonstrated the sensitivity of the serotonergic system of male Fischer 344 rats to both aging and chronic ethanol consumption. In control rats, aging was associated with a decline in the concentration of 5-HT_2A receptors in the nucleus accumbens and four cortical regions: frontal, parietal, piriform, and cingulate cortex. 5-HT_2A receptors were also reduced in the frontal, parietal, and cingulate cortex of aged ethanol-fed rats. In contrast, 5-HT reuptake sites were increased in older rats in the frontal cortex, nucleus accumbens, amygdala, and CA3 region of the hippocampus. If comparable changes in 5-HT_2A receptors and 5-HT reuptake sites occur in elderly humans, they may contribute to ethanol consumption, and lead to cognitive and other age-related problems. These changes may also alter the effectiveness of serotonergic drugs used in the treatment of alcoholism and mental disorders. The effects of chronic ethanol consumption were more limited. The only significant ethanol effect was an increase of 5-HT_2A receptors in the nucleus accumbens of 5-month-old ethanol-fed rats.     

Effects of Maternal Ethanol Consumption and Buspirone Treatment on Dopamine and Norepinephrine Reuptake Sites and D1 Receptors in Offspring

Previously, it was shown that in utero ethanol exposure results in decreased serotonin (5-HT) and altered concentrations of 5-HT reuptake sites and 5-HT_1A receptors in fetal and/or postnatal rats. Because fetal 5-HT is an essential trophic factor, this laboratory previously investigated the hypotheses that the early ethanol-associated 5-HT deficit contributed to subsequent development abnormalities in the serotonergic system and that the effects of the fetal 5-HT deficit could be prevented by maternal treatment with buspirone, a 5-HT_1A receptor agonist. The present report determined the effects of maternal treatment with buspirone on two other neurotransmitter systems in the developing offspring of ethanol-fed dams: dopamine (DA) and norepinephrine reuptake sites and D1 receptors in postnatal day 19 offspring of control and ethanol-fed dams, that received daily injections of saline or 4.5 mg/kg buspirone. These investigations found that in utero ethanol exposure significantly decreased norepinephrine reuptake sites in the dorsomedial hypothalamic nucleus and anteroventral thalamic nucleus. There was also an ethanol effect in the dorsal raphe. D1 receptors were moderately increased (5–10% increase) in the striaturn, and DA reuptake sites were unchanged in PN19 ethanol-exposed offspring. No other significant ethanol-related effects were noted. Maternal buspirone treatment did not adversely affect the concentration of DA reuptake sites or D1 receptors in control rats. Thus, whereas buspirone exerts protective effects on the developing 5-HT system of ethanol-exposed rats, it does not appear to damage the development of the DA system. Maternal buspirone produced only one significant abnormality in control offspring; it resulted in a significant reduction of norepinephrine reuptake sites in the DR.     

The reinforcing properties of salsolinol in the ventral tegmental area: evidence for regional heterogeneity and the involvement of serotonin and dopamine

Background:  Salsolinol (SAL), the condensation product of acetaldehyde and dopamine, may be a factor contributing to alcohol abuse. Previous research indicated that both ethanol and acetaldehyde are self-administered into the posterior ventral tegmental area (VTA). The current study examined SAL self-infusions into the VTA, and determined the involvement of dopamine neurons and 5-HT₃ receptors in this process.
Methods:  The intracranial self-administration technique was used to determine the self-infusion of SAL into the VTA of adult, male Wistar rats. The rats were placed in 2-lever (active and inactive) experimental chambers, and allowed to respond for the self-infusion of 0, 0.03, 0.1, 0.3, 1.0 or 3.0 μM SAL into the posterior or anterior VTA. In a second experiment, rats self-administered 0.3 μM SAL for the initial 4 sessions, co-administered SAL with ICS-205,930 (a 5-HT₃ receptor antagonist) or quinpirole (a D_2,3 receptor agonist) for sessions 5 and 6, and then only 0.3 μM SAL for session 7.
Results:  Wistar rats, given 0.03 to 0.3 μM SAL, received more infusions per session than did the group given artificial cerebrospinal fluid (aCSF) alone (e.g., 41 infusions for 0.1 μM SAL versus 9 infusions for the aCSF group), and responded more on the active than inactive lever. These effects were observed in the posterior but not in anterior VTA. Co-infusion of 100 μM ICS-205,930, or quinpirole significantly reduced self-infusions and active lever responding.
Conclusions:  SAL produces reinforcing effects in the posterior VTA of Wistar rats, and these effects are mediated by activation of DA neurons and local 5-HT₃ receptors.     

Selective Inhibition of Alcohol Intake in Diverse Alcohol-Preferring Rat Strains by the 5-HT2A Antagonists Amperozide and FG 5974

The present studies sought to elucidate the role of 5-HT_2A receptor antagonists in suppressing alcohol intake by comparing the effects of amperozide and FG 5974 on alcohol, food, and water intake in strains of alcohol-preferring rats: P, Alko Alcohol (AA), and Fawn-Hooded (FH). Both amperozide and FG 5974 have 5-HT_2A receptor antagonist properties, but FG 5974 also shows presynaptic 5-HT_1A receptor agonist activity. After establishment of stable baselines for intake measures in a two-bottle continuous access paradigm, rats ( n = 10) were injected with 1 of 5 doses (0, 1.0, 2.5, 5.0, and 10.0 mg/kg, sc) of amperozide or FG 5974 at weekly intervals. Amperozide dose-dependently reduced alcohol intake, total fluid intake, and alcohol preference in all three strains under continuous access conditions, whereas FG 5974 was less effective. Food intake was also suppressed by amperozide at higher doses, whereas it was increased by FG 5974. Amperozide also dose-dependently reduced alcohol intake when it was available for only 1 hr/day, but FG 5974 tended to increase it. After oral administration, amperozide was also more effective than FG 5974 in reducing alcohol intake. Despite these differences in efficacy in suppressing alcohol intake, both compounds produced taste aversion to a novel saccharin solution. These complex findings suggest that biochemical properties other than 5-HT_2A receptor antagonism (e.g., 5-HT_1A receptor agonism) may be involved in the effects of amperozide and FG 5974 on alcohol intake and other consummatory behaviors.     

Additive Reduction of Alcohol Drinking by 5-HT1A Antagonist WAY 100635 and Serotonin Uptake Blocker Fluoxetine in Alcohol-Preferring P Rats

We found previously that alcohol-preferring (P) rats have fewer serotonin (5-HT) neurons and fibers in key brain regions than alcoholnonpreferring (NP) rats. Because 5-HT uptake blockers increase synaptic 5-HT content and 5-HT_1A receptor antagonists increase 5-HT release by disinhibiting 5-HT autoinnervation, in the present study, our intent was to determine whether increased synaptic 5-HT content and/or 5-HT release in P rats would effectively reduce alcohol consumption. In experiment 1, the 5-HT antagonist WAY 100635 (WAY) was tested on adult female P rats maintained on 24-hr free-choice access to ethanol (10% v/v) and water. Twice daily doses of WAY (0.05, 0.1, 0.5, and 1.0 mg/kg, subcutaneously) were administered to each rat in a counterbalanced order. Baseline ethanol intake, derived from the mean ethanol intakes of the three previous non-drug days, was approximately 8 g/kg/day. Results indicated that 0.05,0.1, and 0.5 mg/kg doses of WAY reduced 24-hr ethanol drinking by 25-30% ( p < 0.01) without affecting 24-hr water intake or body weight In the second experiment, the effects of WAY (0.5 mg/kg), fluoxetine (1.0 mg/kg), or a combination of both were tested in another group of female P rats. WAY and fluoxetine, each alone, reduced ethanol drinking by around 20% and, when combined, decreased ethanol intake by 50%, whereas the body weight and the total fluid intake were not significantly affected. Taken together, these results indicate that both fluoxetine and WAY preferentially reduce ethanol drinking in the P line of rats and, when administered together, reduce ethanol intake in an additive manner. It is proposed that coadministration of these two compounds with distinct mechanisms of action may be a new strategy for reducing alcohol intake.     

Association between Low Contents of Dopamine and Serotonin in the Nucleus Accumbens and High Alcohol Preference

The contents of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), serotonin (5-HT), and 5-hydroxy-indoleacetic acid (5-HIAA) were determined in the nucleus accumbens (ACB), frontal cortex (FR), anterior striatum (AST), and hippocampus (HIP) of adult male rats from the F₂ generation of P×NP intercrosses. Rats were tested for their alcohol preference and were divided into two groups, depending on their alcohol intake. Rats in the high drinking group ( n = 11) had ethanol intakes >5 g/kg/day, whereas the low drinking group ( n = 15) had values < 1 g/kg/day. The content of DA in the ACB was lower ( p < 0.001) in the high alcohol drinking group (46 ± 2 pmol/mg tissue) than in the low intake rats (61 ± 3 pmol/mg tissue). However, the contents of DOPAC and HVA in the ACB were similar for both groups. There were no differences between the two groups in the contents of DA in the FR or AST. The content of 5-HT in the ACB was lower (p < 0.05) in high alcohol drinking rats (6.3 ± 0.3 pmol/mg tissue) than in the low intake group (7.0 ± 0.2 pmol/mg tissue). The content of 5-HIAA in the ACB of the high intake rats was also lower than the level for the low drinking rats. There were no differences in the contents of 5-HT or 5-HIAA in the FR, HIP, and AST between the two groups. The results confirm a phenotypic association between abnormal DA and 5-HT systems projecting to the ACB and high alcohol drinking behavior in the P line of rats.     

Serotonin2C Receptors and Serotonin2C Receptor-Mediated Phosphoinositide Hydrolysis in the Brain of Alcohol-Preferring and Alcohol-Nonpreferring Rats

To examine the role of serotonin_2C (5HT_2C) receptors in alcohol drinking behavior, the binding indices of 5HT_2C receptors were determined in various brain regions of alcohol-preferring (P) and alcohol-nonpreferring (NP) rats. 5HT_2C receptor-mediated phosphoinositide hydrolysis in the choroid plexus of P and NP rats was also determined. It was observed that the densities of 5HT_2C receptors are significantly higher in the hippocampus, the amygdala, and the choroid plexus, but not in the cortex of P rats compared with NP rats. The K _d values of [³H]mesulergine binding to 5HT_2C receptors were not different in these brain regions of P rats compared with NP rats. It was also observed that 5HT-stimulated [³H]inositol 1-phosphate formation was significantly higher in the choroid plexus of P rats compared with NP rats. The results of this study indicate that the numbers of 5HT_2C receptors are higher in the hippocampus, the amygdala, and the choroid plexus, and that 5HT_2C receptor-mediated phosphoinositide hydrolysis is more elevated in the choroid plexus of P rats compared with NP rats. Thus, it seems from these results that increased 5HT_2C receptors may be involved in the genetic vulnerability to alcohol drinking behavior.     

Effects of Chronic Alcohol Consumption on Enzyme Activities and Active Methionine Absorption in the Small Intestine of Pregnant Rats

The present study evaluates the effect of chronic alcohol intake on the intestinal transport of methionine during pregnancy. For this purpose, we have used an in vitro technique that allows measurement of the unidirectional influx of the amino acids across the brush-border membrane of the rat mid-jejunum, and the basolateral membrane enzyme Na⁺,K⁺-ATPase was also evaluated in the duodenum and jejunum. For chronic alcohol treatment, the rats were fed a liquid diet containing ethanol (36% of calories) or an isocaloric diet (pair-fed control) for 5 weeks before and during pregnancy. Animals were killed at 21 days of gestation. Results from the kinetic analysis revealed that chronic ethanol treatment reduces the maximum transport (J_m) of methionine uptake when compared with controls. Further experiments performed in the presence and absence of sodium have shown that ethanol selectively inhibited Na⁺-dependent methionine transport. At the same time, this treatment significantly reduced the levels of Na⁺,K⁺-ATPase in ethanol-fed rats compared with the controls. Alterations in methionine intestinal transport in pregnant alcohol-fed rats may contribute to the ethanol-induced fetal growth abnormalities.     

Analysis of the 5-HT2 Receptor Ligands Dimethoxy-4-indophenyl-2-aminopropane and Ketanserin in Ethanol Discriminations

Previous studies have suggested a modulatory role of the 5-HT₂ receptor system in the behavioral effects of ethanol. The present study examined the discriminative stimulus effects of the 5-HT_2A/2C agonist (–)-dimethoxy-4-indophenly-2-aminopropane (DOI) and the 5-HT_2A antagonist ketanserin in rats trained to discriminate either 1.5 g/kg of ethanol from water (intragastrically, n = 7) or 2.0 g/kg of ethanol from water (intragastrically, n = 8). In substitution tests, neither DOI (0.3 to 1.0 mg/kg, ip) nor ketanserin (3.0 to 17.0 mg/kg, ip) produced discriminative stimulus effects similar to either training dose of ethanol, although decreases in rates of responding were significant at the highest doses tested. Likewise, when given in combination with ethanol, neither 5-HT₂ ligand shifted the ethanol-dose response determination in either the 1.5 or 2.0 g/kg ethanol training groups. DOI in combination with ethanol did not alter rates of responding, whereas ketanserin in combination with ethanol significantly decreased response rates. Thus, the 5-HT_2A receptor ligands do not appreciably affect the discriminative stimulus effects of ethanol, in contrast to previous results with 5-HT_1B ligands.     

Comparison of the Effects of Regional Ischemia and Hyperkalemia on the Membrane Action Potentials of the In Situ Pig Heart

APD During Ischemia. Introduction: This study was designed to determine the role of increased extracellular potassium [K⁺]_e on action potential duration (APD) in the in situ porcine heart during acute regional no-flow ischemia.
Methods and Results: In open chest, anesthetized swine, an arterial shunt from the carotid artery to the mid-left anterior descending coronary artery was created through which a solution of KCl was infused to raise [K⁺]_e, Myocardial [K⁺]_e, was determined by potassium-sensitive electrodes, and transmembrane action potential was recorded by floating glass microelectrode. During the first 2 minutes of ischemia, APD at 90% repolarization (APD₉₀) lengthened by 31.2 ± 1.1 msec (P < 0.05). The comparable increase in [K⁺]_e alone shortened APD₉₀, During the next 6 minutes of ischemia. [K⁺]_e, rose to 11.3 ± 0.3 mM and APD₉₀, showed a decrease. However, the comparable increase in |K⁺]_e, by infusion of KCl caused further shortening of APD₉₀, at similar levels of [K⁺]_e.
Conclusions: Acutely ischemic myocardium showed a brief increase in APD₉₀, during the first 2 minutes of ischemia, followed by a fall in APD₉₀, after 2 minutes of ischemia, but the shortening is less than anticipated by the rise in [K⁺]_e. Thus, we hypothesize that other component(s) of ischemia may inhibit action potential repolarization.     

Effects of Chronic Ethanol Exposure on GABA Receptors and GABAB Receptor Modulation of 3H-GABA Release in the Hippocampus

Chronic ethanol treatment (CET), sufficient for decreasing long-term potentiation (LTP) in rats, also enhances ³H-GABA release from hippocampal slices in these same animals. The mechanism for an increase in GABA release may involve changes in presynaptic receptors. Therefore, we characterized presynaptic autoreceptor modulation of ³H-GABA release in hippocampal slices from control and CET rats. The effects of a GABA_B receptor agonist (baclofen) and antagonist [2-hydroxy (OH)-saclofen] were tested for their ability to modulate electrically stimulated ³H-GABA release from superfused hippocampal slices. Baclofen decreased stimulated release in a dose-dependent manner and 2-OH-saclofen increased release consistent with the existence of presynaptic GABA_B autoreceptors in hippocampus. The GABA_A antagonist bicuculline did not significantly modulate basal or stimulated release. When the effects of baclofen and 2-OH-saclofen were measured in animals 48 hr after withdrawal from CET, presynaptic modulation of release by baclofen and 2-OH-saclofen was decreased. In addition, we examined the density of ³H-baclofen and ³H-bicuculline binding in the hippocampal formation using quantitative autoradiographic techniques. We found that the density of ³H-baclofen binding sites was not affected by CET, whereas the density of ³H-bicuculline binding sites was increased by 28% in ethanol-treated rats. These data may explain how CET increases presynaptic regulation of GABA release from hippocampus that may contribute to the decrease in LTP seen in rats after CET.     

The 5-HT3 Antagonist MDL-72222 Exacerbates Ethanol Withdrawal Seizures in Mice

Ethanol-dependent mice were treated with the 5-HT₃ antagonist MDL 72222 after withdrawal from ethanol. Treatment with unit doses (0, 5.6, 10, and 17.0 mg/kg) of MDL 72222 at 0, 4, and 7 hr after withdrawal dose-dependently exacerbated the severity of ethanol withdrawal seizures. Treatment with a single dose (17 mg/kg) of MDL 72222 at 5 hr after withdrawal also exacerbated the severity of ethanol withdrawal seizures. Ethanol naive mice treated with MDL 72222 (56 mg/kg) did not display any seizures. Treatment with another 5-HT₃ antagonist, ICS 205-930 (23 and 46 mg/kg), or the 5- HT₂ receptor antagonist ketanserin, did not affect ethanol withdrawal seizures. The findings suggest MDL 72222 selectively enhances sensitivity to withdrawal seizures following chronic ethanol exposure.     

Dopamine D2 Receptor Gene Expression in Rat Lines Selected for Differences in Voluntary Alcohol Consumption

A selective breeding program has led to the establishment of the alcohol-preferring AA (Alko, Alcohol) and alcohol-avoiding ANA (Alko, Nonalcohol) rat lines. To reveal putative baseline differences in dopamine receptor gene expression and dopamine receptor binding profile in the AA and ANA rat lines, we assessed striatal D₂ mRNA levels in these two rat lines. Autoradiographical studies on dopamine D₁ and D₂ receptors in the striatum and nucleus accumbens were also performed with [³H]SCH 23390 and [¹²⁵I]iodosulpiride/[³H]spiperone, respectively. The baseline differences in D₁ or D₂ receptor binding and D₂ receptor gene expression between AA and ANA rat lines are marginal, and are not likely to play a role in the genetic background of the differential alcohol drinking behavior of these rat lines.     

Demonstration of Central Nervous System Tolerance to Ethanol in Mice: Consequent Effects on Smooth Muscle in Vitro

Mice were given ethanol (9 g/kg) or saline (57 ml/kg) daily in three divided doses for periods of 1 and 4 days to study the effects of such ethanol (ETOH) exposure on central nervous system (CNS) and peripheral smooth muscle (vasa deferentia) function. After 1 day, ETOH-treated mice were functionally tolerant to the hypothermic (3 g/kg, intraperitoneal), but not to the hypnotic (3.25 g/kg, intraperitoneal) effect of ETOH. Functional tolerance to both CNS effects of ETOH was demonstrated in mice after the 4-day ETOH exposure. Norepinephrine (NE) and high K⁺-depolarizing solutions each elicited dose-dependent contractions in the mouse vasa deferens preparation in vitro that consisted of a phasic and tonic component. The tonic components of the NE and K⁺ responses were more dependent upon extracellular Ca²⁺ (Ca²⁺_ext) than the phasic components. Addition of ETOH (120 to 480 mM) or the Ca²⁺ channel-antagonist nifedipine (1× 10+ to 3 × 10⁻-⁷ m) to the preparation selectively inhibited the tonic component of the NE and K⁺ responses, suggesting that both agents acted to inhibit the responses by interfering with the translocation of Ca²⁺_ext. Vasa deferentia isolated from ETOH-treated mice did not exhibit altered reactivity to NE in the phasic or tonic comp nent of the response. The isolated smooth muscle from mice centrally tolerant to ETOH did not appear to be tolerant to the inhibitory effect of ETOH or cross-tolerant to the inhibitory effect of nifedipine on stimulant-induced contractions.     

Effects of Alcohol on Intrauterine Oxygen Tension in the Rat

The effects of alcohol on the availability of oxygen within the uterine lumen of rats were determined on Day 4 of pseudopregnancy. Intraluminal oxygen tension (pO₂) was measured in vivo in anesthetized rats using a 22-gauge polarographic oxygen sensor. Intrauterine pO₂ was measured for 15 min before and after intravenous injection of alcohol (1.0 g/kg: 100% ethanol/saline, 1:2 v/v) or vehicle (physiological saline). Alcohol administration increased mean intrauterine pO₂ (mm Hg) from a pretreatment level of 28.3 ± 2.8 to 38.7 ± 3.8 mm Hg ( p < 0.05, n = 10) at 15 min postinjection. The rapid rise in oxygen tension was accompanied by increased frequency of fluctuation (peaks/hr) in intraluminal pO₂ (prealcohol: 64.2 ± 8.8 vs. postalcohol 96.0 ± 7.7 peaks/hr; ( p < 0.05, n = 10). Injection of saline did not alter any aspect of intrauterine pO₂. During the period of measurement of luminal pO₂, blood alcohol levels increased from 0 during pretreatment to 106 mg% within 10 min of injection. These results indicate that alcohol increases the availability of oxygen within the uterus during the time of endometrial sensitivity to deciduogenic stimuli and blastocyst implantation.     

Melatonin reduces H2O2-induced lipid peroxidation in homogenates of different rat brain regions

Abstract: The ability of melatonin to modify H₂O₂-induced lipid peroxidation in brain homogenates was determined. The concentrations of brain malonaldehyde (MDA) and 4-hydroxyalkenals (4-HDA) were assayed as an index of induced membrane oxidative damage. Homogenates from five different regions of the brain (cerebral cortex, cerebellum, hippocampus, hypothalamus, and corpus striatum) derived from two different strains of rats, Sprague-Dawley and Wistar, were incubated with either H₂O₂ (5 mM) alone or H₂O₂ together with melatonin at increasing concentrations ranging from 0.1 to 4 mM. The basal level of lipid peroxidation was strain-dependent and about 100% higher in homogenates from the brain of Wistar rats than those measured in Sprague-Dawley rats. MDA + 4-HDA levels increased after H₂O₂ treatment in homogenates obtained from each region of the brain in both rat strains but the sensitivity of the homogenates from Sprague-Dawley rats was greater than that for the homogenates from Wistar rats (increases after H₂O₂from 45 to 165% compared 20 to 40% for Sprague-Dawley and Wistar rats, respectively). Melatonin co-treatment reduced H₂0₂-induced lipid peroxidation in brain homogenates in a concentration-dependent manner; the degree of protection against lipid peroxidation was similar in all brain regions.