Positive modulation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors elicits neuroprotection after trimethyltin exposure in hippocampus

Experiments were designed to determine if gender influences the cardiac toxicity elicited by chronic high-level ethanol intake. Male and female ethanol-preferring P-rats were allowed free access to drinking water or water containing 25% ethanol for 6 months. Left atrial preparations were then isolated, bathed in Krebs-Henseleit solution (37 degrees C), and used to examine basal contractility at 3.0 Hz stimulation, the force-frequency relationship, and the positive inotropic response to the beta-adrenoceptor agonist isoproterenol. Basal contractile function was not affected significantly by ethanol in either gender; however, atria from ethanol-treated male rats displayed diminished contractility compared to control males when measured at slow stimulation frequencies (0.1 and 0.2 Hz), during post rest potentiation (at rest intervals of 20-60 s), and in response to higher concentrations of isoproterenol (> or =3 x 10(-7) M; EC50 values were not affected). In contrast, female atria showed no effect of chronic ethanol consumption. These data suggest that ethanol consumption diminishes the cardiac reserve in male, but not female rats.     

Gender-specific vascular effects elicited by chronic ethanol consumption in rats: a role for inducible nitric oxide synthase

BACKGROUND AND PURPOSE: Epidemiological data suggest that the risk of ethanol-associated cardiovascular disease is greater in men than in women. This study investigates the mechanisms underlying gender-specific vascular effects elicited by chronic ethanol consumption in rats. EXPERIMENTAL APPROACH: Vascular reactivity experiments using standard muscle bath procedures were performed on isolated thoracic aortae from rats. mRNA and protein for inducible NO synthase (iNOS) and for endothelial NOS (eNOS) was assessed by RT-PCR or western blotting, respectively. KEY RESULTS: In male rats, chronic ethanol consumption enhanced phenylephrine-induced contraction in both endothelium-intact and denuded aortic rings. However, in female rats, chronic ethanol consumption enhanced phenylephrine-induced contraction only in endothelium denuded aortic rings. After pre-incubation of endothelium-intact rings with L-NAME, both male and female ethanol-treated rats showed larger phenylephrine-induced contractions in aortic rings, compared to the control group. Acetylcholine-induced relaxation was not affected by ethanol consumption. The effects of ethanol on responses to phenylephrine were similar in ovariectomized (OVX) and intact (non-OVX) female rats. In the presence of aminoguanidine, but not 7-nitroindazole, the contractions to phenylephrine in rings from ethanol-treated female rats were greater than that found in control tissues in the presence of the inhibitors. mRNA levels for eNOS and iNOS were not altered by ethanol consumption. Ethanol intake reduced eNOS protein levels and increased iNOS protein levels in aorta from female rats. CONCLUSIONS AND IMPLICATIONS: Gender differences in the vascular effects elicited by chronic ethanol consumption were not related to ovarian hormones but seemed to involve the upregulation of iNOS.     

Effect of ethanol consumption on blood pressure and rat mesenteric arterial bed, aorta and carotid responsiveness

This study investigates whether chronic ethanol consumption increases blood pressure and alters vascular reactivity in different tissues. Changes in reactivity to phenylephrine and acetylcholine were investigated in the aorta, carotid artery and mesenteric arterial bed (MAB) isolated from rats pretreated with ethanol for 2 or 6 weeks. Mild hypertension was observed in chronically ethanol-treated rats, which was due to rises in both systolic and diastolic pressures. Chronic ethanol consumption increased the contractile response to phenylephrine of endothelium-intact and denuded rat aortic rings from rats pretreated with ethanol for 2 or 6 weeks. Conversely, no differences were found in acetylcholine-induced relaxation. Neither phenylephrine-induced contraction nor acetylcholine-induced relaxation were altered in the rat carotid. Six weeks' ethanol consumption enhanced the contractile response to phenylephrine of endothelium-intact, but not denuded rat MAB. On the other hand, 2 weeks' ethanol consumption did not affect phenylephrine-induced increase in perfusion pressure. Moreover, acetylcholine-induced endothelium-dependent relaxation in the MAB was reduced after treatment with ethanol for 6 weeks but not after 2 weeks. In conclusion, ethanol affects both blood pressure and vessel reactivity, but the effect on vascular reactivity may take longer to become apparent in MAB than in the aorta, and was not evident in the carotid. Moreover, we provide evidence that the effect of ethanol depends on the agonist and blood vessel studied.     

Sex differences in L-type calcium current after chronic ethanol consumption in rats

Chronic ethanol consumption elicits a progressive cardiac contractile dysfunction, and studies in rats suggest that this alcoholic heart muscle disease is more pronounced in males than females. Cellular changes associated with the ethanol-induced cardiotoxicity remain largely undefined; however, it is possible that L-type Ca(2+) channel current (I(Ca,L)) is affected. Using whole-cell patch-clamp techniques, this study examined I(Ca,L) in adult ventricular myocytes isolated from male and female P-rats that had consumed drinking water (controls) or a 25% ethanol/water mixture for 14 months. The peak amplitude and maximum conductance of I(Ca,L) were 32 and 26% greater, respectively, in cardiomyocytes isolated from ethanol-consuming compared to control male rats. In contrast, no differences in the amplitude or conductance of I(Ca,L) were observed when comparing myocytes isolated from control and ethanol-consuming females. Ethanol treatment had no significant effects on the kinetics I(Ca,L) inactivation or on steady-state activation and inactivation in either gender. In conclusion, male but not female cardiomyocytes respond to chronic ethanol consumption with an increased I(Ca,L) that may represent a compensatory response to the depressed contractility.     

Increase in free choice oral ethanol self-administration in catechol-o-methyltransferase gene-disrupted male mice

The effect of catechol-O-methyltransferase (Comt) gene disruption on the voluntary oral consumption of water, ethanol (2.5-20%, v/v) and cocaine (0.1-0.8 mg/ml) was studied in the free-choice, two-bottle paradigm in male and female mice. Solutions containing ethanol or cocaine, or tap water were available ad libitum from drinking burettes for 4 weeks. Catechol-O-methyltransferase-deficient male mice consumed significantly more ethanol than their wild-type male littermates. In contrast, female mice did not show genotype differences in the consumption of ethanol solutions. During the cocaine experiment, male mice developed either a side preference or an aversion that obscured cocaine consumption. This pattern of drinking was not dependent on Comt genotype. In female mice, Comt genotype was not associated with cocaine consumption. In conclusion, disruption of Comt gene influenced ethanol consumption in a gender-dependent manner in mice, supporting the hypothesis that low catechol-O-methyltransferase activity is one of the predisposing factors for high alcohol consumption in males.     

Daily patterns of ethanol drinking in adolescent and adult, male and female, high alcohol drinking (HAD) replicate lines of rats

The rationale for our study was to determine the pattern of ethanol drinking by the high alcohol-drinking (HAD) replicate lines of rats during adolescence and adulthood in both male and female rats. Rats were given 30 days of 24 h free-choice access to ethanol (15%, v/v) and water, with ad lib access to food, starting at the beginning of adolescence (PND 30) or adulthood (PND 90). Water and alcohol drinking patterns were monitored 22 h/day with a “lickometer” set-up. The results indicated that adolescent HAD-1 and HAD-2 males consumed the greatest levels of ethanol and had the most well defined ethanol licking binges among the age and sex groups with increasing levels of ethanol consumption throughout adolescence. In addition, following the first week of adolescence, male and female HAD-1 and HAD-2 rats differed in both ethanol consumption levels and ethanol licking behavior. Adult HAD-1 male and female rats did not differ from one another and their ethanol intake or licking behaviors did not change significantly over weeks. Adult HAD-2 male rats maintained a relatively constant level of ethanol consumption across weeks, whereas adult HAD-2 female rats increased ethanol consumption levels over weeks, peaking during the third week when they consumed more than their adult male counterparts. The results indicate that the HAD rat lines could be used as an effective animal model to examine the development of ethanol consumption and binge drinking in adolescent male and female rats providing information on the long-range consequences of adolescent alcohol drinking.     

Social structure and ethanol consumption in the laboratory rat

When mixed-sex groups of rats in established colonies were given free access to 4% and then 8% ethanol solutions, relative ethanol consumption for individual subjects was consistent over the two solutions, with some subordinate males consuming much more ethanol than any of the dominant males. Overall, subordinate male consumption was significantly higher than that of dominants, suggesting that the social stress of subordination may be a factor in ethanol consumption. Offensive attack was reduced under 8% consumption conditions, compared to the pre-ethanol level. The significant negative correlation between initial offense level and the level of offense seen under 8% ethanol consumption agrees with previous work suggesting that more offensive males show a differential decline in offense with ethanol. Female colony members consumed significantly more ethanol than males, with some suggestion of increased drinking in response to social stresses. This pattern of results suggests that the colony situation may provide an important model for investigation of the relationship between social stress and ethanol consumption.     

Effect of swimming on vascular reactivity to phenylephrine and KC1 in male rats.

1. The present study aimed to examine whether there is any change in vascular responsiveness to phenylephrine and KC1 during exercise, and whether the vascular endothelium plays a role in these changes. 2. Adult male rats were subjected to a swimming schedule every day for 5-6 weeks. Studies were performed in vitro on thoracic aortae. 3. Maximum contractile response to phenylephrine of endothelium-intact thoracic aortic rings (passive tension 1.0 g) obtained from swimming rats (1.2 +/- 0.2 g, n = 8) was lower than of sedentary control rats (2.1 +/- 0.2 g, n = 8). When the endothelium was removed, however, the dose-response curves of both groups of rats were shifted to the left with an increase in maximum responses and they were no longer significantly different (max. tension, swimming rats: 3.2 +/- 0.3 g, n = 6, control rats: 3.4 +/- 0.4 g, n = 5). 4. Indomethacin did not significantly alter the dose-response curves. A similar effect to that obtained by removal of the endothelium was observed when methylene blue and indomethacin were both added. 5. Passive tension in the range of 2.5-3.0 g, caused a significant increase in active tension developed to phenylephrine (1 microM for endothelium-intact and 0.1 microM for endothelium-denuded) of thoracic aortic rings of both swimming and sedentary control rats compared to their corresponding groups when using passive tension of 1.0-1.5 g. 6. The reduction in responses to phenylephrine of endothelium-intact thoracic aortic rings of swimming rats persisted with the use of a passive tension of 3.0 g.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chronic ethanol consumption alters vascular smooth muscle responses in rats

1. The effect of chronic ethanol (10%) consumption for 5 months on vascular smooth muscle (VSM) using aortic rings of both sexes of Sprague-Dawley rats was studied. 2. Chronic ethanol consumption increased the sensitivity of VSM to noradrenaline (NA) in both male and female ethanol-treated rats. 3. There was no significant difference in the contractile response of male and female ethanol-treated rats to NA. Hence, the enhancement of vascular contractility to the agonist due to chronic ethanol consumption is independent of gender. 4. Vascular relaxation induced by acetylcholine showed similar responses in all experimental groups. Thus, chronic ethanol consumption seems to have no significant effect on the production of endothelium-dependent relaxing factor. 5. However, the VSM sensitivity to potassium chloride was increased in female ethanol-treated rats, whereas male ethanol-treated rats had similar responses as controls. 6. The results suggest that the effect of chronic ethanol consumption on VSM varies with gender. Impairment of VSM in male ethanol-treated rats is due partly to changes in the receptor-operated channel, whereas in females it is due to changes in both receptor- and potential-operated channels.     

Patterns of ethanol and water consumption as a function of restricted ethanol access and feeding condition

Sixteen male albino rats were divided into two groups of eight animals and maintained at either their free-feeding or at 80% of their free-feeding weight. For four animals, access to 8% ethanol was unrestricted, for the remaining four, access was restricted to eight 20-min access periods per day. Mean amounts of ethanol consumed per bout were greater during restricted access than during unrestricted access for food-deprived animals but not for free-feeding animals. Total daily ethanol consumption was greatest when animals were food deprived and access to ethanol unrestricted. Total fluid consumption and the within session distribution of water and ethanol responding were affected by feeding condition. For food-deprived animals, the amount of water consumed per session remained relatively constant. The increase in ethanol consumption over sessions resulted in an increase in total fluid consumption. For the free-feeding animals, increases in ethanol consumption resulted in decreases in water consumption so that total fluid consumption remained constant. In addition, food-deprived animals consumed all their daily water intake at the beginning of each session when food was present. Free-feeding animals consumed water throughout the session.     

Studies on the effect of chronic consumption of moderate amounts of ethanol on male rat hepatic microsomal drug-metabolizing activity

Weanling, male Sprague-Dawley rats given 10% ethanol in the drinking water and food ad lib. for up to 8 weeks consumed 17% of their calories as ethanol. The alanine aminotransferase (ALT), aspartate aminotransferase (AST), and liver histology by light microscopy were unaffected by this treatment. Similarly, hepatic microsomal NADPH-cytochrome c reductase, ethylmorphine N-demethylase and benzphetamine N-demethylase activities were also not affected by ethanol consumption. On the other hand, cytochrome P-450 content, aniline hydroxylase activity and acetaminophen metabolism as measured by both the cysteine conjugate and the [3H]acetaminophen covalently-bound to microsomal protein were increased significantly by ethanol consumption. The maximal effect was seen by 6 weeks. The 2- to 3-fold increase in aniline and acetaminophen metabolism, the absence of liver damage, and the similarity in weight gains and caloric intakes for controls and treated animals suggest that the rat on 10% ethanol in the drinking water is a reasonable model for studies of the effect of moderate alcohol consumption on specific biochemical pathways.     

An analysis of the inhibitory effects of prazosin on the phenylephrine response curves of the rat aorta

Summary On the endothelium-intact rat aorta some studies have shown prazosin to cause nonparallel rightward shifts of ₁-adrenoceptor agonist response curves. The aim of the present study was to analyze the inhibitory effect of prazosin on the phenylephrine responses of the endothelium-intact and endothelium-denuded rat aorta. Firstly I used phenoxybenzamine treatment to characterize the phenylephrine responses. The K_A values for phenylephrine were 0.13–0.18 M and 0.07–0.16 M in the endothelium-intact and endothelium-denuded rat aorta, respectively. In order to produce maximal responses of the endothelium-intact or — denuded preparation, phenylephrine had to occupy 95–99% of the ₁-adrenoceptors.Secondly I compared the inhibitory effects of phentolamine and prazosin on the endothelium-intact rat aorta. Phentolamine at 0.1 and 1 M caused parallel rightward shifts of phenylephrine response curves with no effect on phenylephrine maximal responses (phentolamine pA₂ = 7.9). The inhibitory effects of phentolamine were readily reversible. Prazosin at 0.1–10 nM caused nonparallel rightward shifts of the phenylephrine response curves with a depression of the maximal response. These inhibitory effects of prazosin were either irreversible or only very slowly reversible in drug-free solution and slowly reversible in the presence of phentolamine. Ninety min was required for the inhibitory effect of prazosin to reach equilibrium whereas phentolamine was at equilibrium after 45 min. Finally I have characterized the inhibitory actions of prazosin on the endothelium-denuded rat aorta. Prazosin caused parallel rightward shifts of phenylephrine response curves with no effect on phenylephrine maximal responses. The inhibitory effects of prazosin were at equilibrium after 45 min and were readily reversible.In conclusion prazosin is a readily reversible ₁-adrenoceptor antagonist in the endothelium-denuded but not in the endothelium-intact rat aorta. It seems likely that the endothelium accumulates or binds prazosin strongly so that the inhibitory action of prazosin is apparently slowly reversible in the endothelium-intact rat aorta.     

Diphasic effects of Astragalus membranaceus BUNGE (Leguminosae) on vascular tone in rat thoracic aorta

This study was designed to investigate the effects of the aqueous ethanol extract of Astragalus membranaceus BUNGE (Leguminosae) on rat thoracic aorta. Isometric tension was recorded in response to drugs in organ bath. In endothelium-intact aortic rings, A. membranaceus extract induced a significant dose-dependent relaxation of the rings precontracted by phenylephrine, which could be inhibited by preincubation with L-N(omega)-nitro-arginine methyl ester or methylthioninium chloride. In endothelium-denuded ones, the extract could dose-dependently relax the rings contracted by phenylephrine, not by KCl; and it could also attenuate contractile response to phenylephrine, not to caffeine or phorbol-12,13-diacetate in Ca(2+)-free medium; but it failed to affect the CaCl(2)-induced enhancement of contractile response to phenylephrine in Ca(2+)-free medium. These results indicate that nitric oxide signaling and Ca(2+)-handling pathway are involved in the A. membranaceus extract-induced vasodilatation.     

Mechanisms involved in the vasodilator effect of the flavanol floranol in rat small mesenteric arteries

The mechanism underlying the vasodilator effect of the flavonoid floranol was studied in rat small mesenteric arteries. Floranol produced a concentration-dependent vasorelaxant effect in endothelium-containing and endothelium-denuded vessels pre-contracted with phenylephrine, which was more potent in endothelium-intact vessels. In endothelium-intact mesenteric arteries, l-NAME but not indomethacin produced a shift to the right in the vasorelaxant effect of floranol. In endothelium-denuded vessels TEA and BaCl2 did not change the floranol-induced vasorelaxation. When endothelium-denuded vessels were pre-contracted with 50 mM KCl, floranol induced a vasorelaxant effect comparable with phenylephrine pre-contracted vessels. We conclude that floranol is a new vasodilator compound in rat small mesenteric arteries. Part of this effect is dependent on endothelial nitric oxide (NO) and part is dependent on the inhibition of voltage-dependent calcium channels in the smooth muscle cells.     

Mechanisms underlining gender differences in Phenylephrine contraction of normoglycaemic and short-term Streptozotocin-induced diabetic WKY rat aorta

The female gender reduces the risk, but succumbs more to cardiovascular disease. The hypothesis that short-term (8weeks) Streptozotocin-induced diabetes could produce greater female than male vascular tissue reactivity and the mechanistic basis were explored. Aortic ring responses to Phenylephrine were examined in age- and sex-matched normoglycaemic/diabetic rats. The normoglycaemic male tissue contracted significantly more than the normoglycaemic female and the male/female diabetic tissues. Endothelial-denudation, l-NAME or MB reversed these differences suggesting an EDNO-cGMP dependence. 17β-oestradiol exerted relaxant effect on all endothelium-denuded (and normoglycaemic endothelium-intact male) tissues, but not endothelium-intact normoglycaemic female. The greater male tissue contraction is attributable to absent 17β-oestradiol-modulated relaxation. Indomethacin blockade of COX attenuated male normoglycaemic and female diabetic tissue contraction (both reversed by l-NAME), but augmented diabetic male tissue contraction. These data are consistent with the raised contractile TXA(2) and PGE(2) in normoglycaemic male and diabetic female tissues, and the relaxant PGI(2) in diabetic male (and female). The higher levels of PGI(2) in the normoglycaemic and diabetic female perhaps explain their greater relaxant response to Acetylcholine compared to the respective male. In conclusion, there is an endothelium-dependent gender difference in the effect of short term diabetes on vascular tissue reactivity which is COX mediated.     

Consumption of intoxicating beverages by rats and mice exhibiting high and low preferences for ethanol

Lines of rats selectively bred for alcohol consumption or avoidance (AA and ANA, ALKO, Finland) as well as inbred strains of mice (C57/BL/6J and DBA/2J) and common female Wistar rats (Charles River) exhibiting high and low preferences for ethanol were tested under free-choice conditions for their consumption of solutions of ethanol (5, 10, or 15 g/100 ml tap water), sodium pentobarbital (0.19, 0.038, 0.076 g/100 ml tap water), and different beverages containing ethanol in the range of 8.1–9.6% (red and white wine, Scotch, ethanol in Hawaiian Punch). The Wistar rats and the mice classified as alcohol-preferring also tended to consume more of the pentobarbital solution than did alcohol-avoiding animals. Alcohol-nonaccepting (ANA) rats, however, consumed considerably more of all three pentobarbital solutions than did the alcohol-accepting (AA) rats. The intake of pentobarbital by the ANA rats and C57/BL/6J mice was in the range of 25–40 mg/kg/day, quantities that might be expected to produce pharmacological effects discriminable by those animals. The intake of ethanol by ANA rats was markedly elevated when the ethanol was contained in white wine or in punch.     

Effects of acute and chronic administration of delta 9-tetrahy-drocannabinol or cocaine on ethanol intake in a rat model.

The acute and chronic administration of delta 9-tetrahydrocannabinol (delta 9-THC) or cocaine were studied in rats trained to obtain all of their daily food by lever pressing during four equally-spaced 30-min periods with water and 5% or 7.5% ethanol solutions freely available. With 5% ethanol available, rats consumed almost all of their daily fluid intake as ethanol, while with 7.5% ethanol available, rats consumed water and ethanol solution in approximately equal amounts. Rats consumed more food pellets with 7.5% ethanol available than with 5% ethanol available. Acute administration of delta 9-THC produced a dose-dependent decrease of 5% ethanol intake and food pellets consumed with a small increase in water intake, especially after the higher doses. Acute administration of delta 9-THC also depressed food intake when 7.5% ethanol was available, but decreases in ethanol solution intake were small. Chronic administration of delta 9-THC initially decreased ethanol intake, but tolerance occurred to this effect, so that during chronic delta 9-THC administration ethanol intake not only recovered, but increased above control levels. When the chronic administration of delta 9-THC was discontinued, ethanol intake was increased for 1 (5% ethanol) to 3 (7.5% ethanol) weeks. Animals with initially high, or initially low, but not with initially moderate ethanol intake, accounted for the increased ethanol intake during chronic delta 9-THC administration and withdrawal. Acute cocaine administration, at doses up to 30 mg/kg, had little effect on eating and drinking; however, during chronic cocaine administration, ethanol intake gradually increased, an increase which was sustained during cocaine withdrawal. The increased ethanol drinking was confined to the first 6-h period after cocaine administration. These data suggest that the chronic administration and withdrawal of other drugs can increase ethanol intake in this rat model.     

Effects of sweetened ethanol solutions on ethanol self-administration and blood ethanol levels

The enhancement of voluntary self-administration of ethanol by sucrose or saccharin was tested in conjunction with measurements of blood ethanol levels. Adult male rats were given access to both tap water and one of five solutions: 0.125% saccharin, 10% sucrose, ethanol, saccharin+ethanol, or sucrose+ethanol. The rats receiving the sucrose+ethanol solution drank consistently more ethanol (>5 g/kg/day) than did the rats receiving the saccharin+ethanol solution (<3 g/kg/day) or ethanol only (<2 g/kg/day). Both sweetened solutions produced higher ethanol consumption during these periods than ethanol alone. However, no significant differences in blood ethanol levels were found between the sucrose+ethanol and saccharin+ethanol conditions, when tested at different intervals on Day 44 or Day 45 of ethanol consumption. Following 45 days of consumption, no change in the bicuculline seizure threshold was observed in the ethanol-consuming rats compared to the controls. In a separate study using 90 naive rats, rats were gavaged with ethanol (1, 2, or 3 g/kg) containing either 10% sucrose (n=10 for each dose of ethanol), 0.125% saccharin (n=10 for each dose of ethanol), or ethanol alone (n=10 for each dose of ethanol), and blood was collected from the tip of the tail 30, 60, 180, 300, and 540 min later and analyzed for ethanol concentrations. Sucrose significantly decreased the resultant blood ethanol levels at several time points following gavage. These results indicate that sucrose can significantly alter blood ethanol levels and that chronic self-administration of a sweetened ethanol solution for 6 weeks does not produce ethanol dependence.     

The effects of cadmium on the self-administration of ethanol and an isocaloric/isohedonic equivalent

During a period of baseline fluid intake recording, adult male rats were presented with a three-bottle, two-fluid choice test that offered either a 10% ethanol solution (v/v) and tap water as alternatives, or a sucrose/quinine solution and tap water as alternatives. The sucrose/quinine solution was equivalent to the ethanol solution both in terms of calories and palatability. After intakes stabilized, half of the animals from each test condition were placed on a diet containing 100 ppm cadmium and the remaining half of the animals were placed on a standard laboratory diet. After 60 days of exposure to their respective diets, all animals were presented their earlier test solutions, both in a nonchoice and choice format. The results from the choice test indicated that although cadmium treatment did not produce a clear preference for ethanol over water, cadmium exposure was associated with a significant increase in ethanol consumption. Moreover, the self-administration of the isocaloric/isohedonic equivalent (sucrose/quinine solution) was unaffected by cadmium contamination. These data are discussed in terms of their implications for both nutritional and sensory-impairment accounts of metal-related changes in the volitional intake of ethanol.