Effect of operant self-administration of 10% ethanol plus 10% sucrose on dopamine and ethanol concentrations in the nucleus accumbens

Although operant ethanol self-administration can increase accumbal dopamine activity, the relationship between dopamine and ethanol levels during consumption remains unclear. We trained Long-Evans rats to self-administer escalating concentrations of ethanol (with 10% sucrose) over 7 days, during which two to four lever presses resulted in 20 min of access to the solution with no further response requirements. Accumbal microdialysis was performed in rats self-administering 10% ethanol (plus 10% sucrose) or 10% sucrose alone. Most ethanol (1.6 +/- 0.2 g/kg) and sucrose intake occurred during the first 10 min of access. Sucrose ingestion did not induce significant changes in dopamine concentrations. Dopamine levels increased within the first 5 min of ethanol availability followed by a return to baseline, whereas brain ethanol levels reached peak concentration more than 40 min later. We found significant correlations between intake and dopamine concentration during the initial 10 min of consumption. Furthermore, ethanol-conditioned rats consuming 10% sucrose showed no effect of ethanol expectation on dopamine activity. The transient rise in dopamine during ethanol ingestion suggests that the dopamine response was not solely due to the pharmacological properties of ethanol. The dopamine response may be related to the stimulus properties of ethanol presentation, which were strongest during consumption.     

Formation of alcohol motivation under blockade of protein synthesis by cycloheximide]

The influence of protein blocker cycloheximide on ethanol intake in rats under condition of development of alcohol motivation was studied. It was found that intracerebroventricular injection of cycloheximide caused inhibition of alcohol intake in rats which had free choice between water and 20% ethanol solution. The blockade action of cycloheximide on the development of alcohol motivation was dependent on initial preference of ethanol in rats and was more strong in rats with originally low preference for ethanol.     

Effects of inmecarb on alcohol intake and the state of hepatic cytochrome P-450 system during various stages of experimental alcoholism in rats

The influence of the new anti-alcohol drug Inmecarb on the alcohol consumption as well as on activity of the liver cytochrome P-450 system was studied in rats during chronic alcohol intoxication in the free choice situation between water and 15% ethanol solution. It was shown that voluntary alcohol consumption of different duration (10 days to 8 months) does not change the activity of liver cytochrome P-450 system. Inmecarb treatment (40 mg/kg, i.p. twice a day) during 14 days resulted in decrease of alcohol consumption in rats. This effect was most pronounced in late stages of experimental alcoholism. Inmecarb decreases the cytochrome P-450 content and suppresses the activity of aniline hydroxylase in rats with different duration of voluntary alcohol intoxication, but most pronounced effect was observed during the late stages of experimental alcoholism.     

Possible correlations between the level of alcoholic motivation and the electrophysiological structure of sleep in the rat

Using modified Porsolt's method, the electrophysiological sleep pattern was studied in normal conditions and after a single intraperitoneal ethanol injection to noninbred male albino rats divided into 2 groups ("high activity" and "low activity" rats). Voluntary alcohol intake in these rats was measured during free choice between 10% ethanol and water for 20 days. "Low activity" rats were characterized by a statistically significant 3.4-fold higher level of ethanol consumption and 2.7-fold longer REM-sleep stage, as compared to "high activity" animals. In "low activity" animals ethanol (1 g/k, 10% solution, i. p.) inhibits and in "high activity" rats it increases REM-sleep stage, thus removing differences in the sleep pattern in the two groups of rats. The data obtained suggest a possible role of REM-sleep in the development of alcohol motivation.     

Ethanol-induced hypothermia and ethanol consumption in the rat are affected by low-level microwave irradiation

Microwave irradiation of rats by circularly polarized, 2,450-MHz, pulsed waves (2-μs pulses; 500 pps) was performed in waveguides to determine effects on ethanol-induced hypothermia and on ethanol consumption. Rats injected intraperitoneally with ethanol (3 g/kg in a 25% v/v water solution) immediately after 45 min of microwave irradiation exhibited attenuation of the initial rate of fall in body temperature, which was elicited by the ethanol, but exhibited no significant difference in maximal hypothermia as compared with that of sham-irradiated rats. Microwave irradiation did not affect the consumption of a 10% sucrose (w/v) solution by water-deprived rats. However, it enhanced the consumption of a solution of 10% sucrose (w/v) + 15% ethanol (v/v) by water-deprived animals. These results were obtained at a specific absorption rate (SAR) of 0.6 W/kg, which rate of energy dosing would require a power density of 3–6 mW/cm² if exposure of the animals had occurred to a 12-cm plane wave.     

Modulations of rabbit erythrocyte ATPase activities induced by in vitro and in vivo exposure to ethanol

Alcohol intake is associated with numerous degenerative disorders, and the detrimental effects of alcohol may be due to its influence on plasma membrane and cellular transport systems. The aim of the present study was to compare in vitro and in vivo effects of ethanol on rabbit erythrocyte ATPase activities and correlate them with ethanol-induced oxidative stress. Age-matched male rabbits were given 5% ethanol in 2% sucrose solution, for 6 weeks ad libitum; control animals were given tap water. Daily intake of ethanol was 5 g/kg body weight; this experimental regimen resulted in an average serum ethanol concentration of 16.77 ± 2.00 mM/l. After this period, blood was collected, serum ethanol concentration was determined and erythrocyte membranes were prepared according to the method of Post et al. Activities of Na⁺/K⁺- and Mg²⁺-ATPases were determined. Thiobarbituric acid-reactive substance (TBARS) assay was used to detect levels of lipid peroxidation, a major indicator of oxidative stress. In vitro ethanol inhibits both Na⁺/K⁺-ATPase and Mg²⁺-ATPase, but Na⁺/K⁺-ATPase is more sensitive to the ethanol-induced inhibition. Increasing concentration of ethanol increased TBARS production, but significant difference was attained only at 5 and 12.5 mM of ethanol. Chronic ethanol consumption induced significant increase in Na⁺/K⁺- and Mg²⁺-ATPase activity, and TBARS production. Our results suggest that increased ATPase activity induced by chronic ethanol consumption is due to oxidative, induced modification of membrane phospholipids and proteins, which are responsible for inhibition of ATPase activity. Increased production of TBARS induced by in vitro exposure to ethanol is not the only factor that influences ATPases activity. Further research is needed to elucidate this relationship.     

The immunization of white rats with a covalent conjugate of sidnofen and serum albumin suppresses chronic ethanol consumption

The influence of white rats of alcohol abuse formation of immunization by covalent conjugates of serum albumin with psychostimulant sydnophen was investigated. Immunization by conjugates where the molar sydnophen: protein ratio was 18:1-33: 1 results in significant depression of 15% ethanol consumption (in the condition of free choice between water and ethanol solution).     

The influence of substance P central administration on ethanol intake in rats chronically exposed to alcohol

The influence of central substance P (SP) administration on alcohol intake and brain dopamine metabolism within mesocortico-limbic and nigrostiatal systems of rats exposed to ethanol, was studied. During 6 months, the rats consumed 15% ethanol solution instead of water. Central administration of SP (3 mcg/kg) decreased alcohol consumption by 41% in alcohol-preference animals. After long-term ethanol exposure ratios DOPAC/DA and HVA/DA were reduced in striatum and accumbens. SP in dose 3 mcg/kg increased content of DOPAC by 17% and HVA by 23% as well as DOPAC/DA by 9%, HVA/DA by 19% in accumbens. Whereas in striatum only increased DOPAC (28%) and HVA (29%) were observed as compared with saline-treated rats.     

Sphingolipid Turnover in the Hippocampus and Cognitive Dysfunction in Alcoholized Rats: Correction with the Help of Alimentary <Emphasis Type="Italic">n</Emphasis>-3 Fatty Acids

We studied the effect of long-lasting (during 60 days) consumption of 15% ethanol solution by 2- to 4-month-old rats on the turnover of sphingolipids in the hippocampus and cognitive functions in these animals. It was found that chronic action of ethanol led to a decrease in the content of newly synthesized sphingomyelin and to an increase in the level of ceramide and the ceramide/sphingomyelin ratio in the hippocampus; this was accompanied by significant worsening of conditioned-reflex activity in experimental rats (testing of active avoidance in a shuttle chamber). The addition of fish oil containing a considerable amount of n-3 fatty acids to the diet of animals consuming ethanol prevented, to a considerable extent, the development of disorders of sphingolipid turnover and cognitive functions.     

The effect of acute and chronic ethanol administration on serum corticosterone concentration in rats

The effect of intraperitoneally (i.p.) and intragastrically (i.g.) administered ethanol solution, and the influence of voluntary ethanol uptake (20% v/v) on adrenocortical activity of adult male rats was studied. Both i.p. and i.g. ethanol administration resulted in a significant activation of adrenocortical mechanisms, while voluntary ethanol uptake failed to induce elevation of serum corticosterone concentration. No difference was found in blood ethanol concentration among these groups. The responsiveness of adrenocortical mechanisms was also tested in rats which were given the free choice between ethanol solution (5% v/v) and tap-water for three weeks. Unavoidable electric foot-shocks, as stressor, resulted in an elevation of serum corticosterone concentration in control animals, but this response was found to be significantly reduced in chronically ethanol drinking rats.     

NAD+-dependent retinol dehydrogenase in liver microsomes

A microsomal NAD+-dependent retinol dehydrogenase is being described with optimal activity at physiological pH. The enzyme was present in liver microsomes of rats and also in a strain of deermice which lacks the cytosolic retinol dehydrogenase. Unlike the latter enzyme, the microsomal retinol dehydrogenase was not inhibited by either ethanol or 4-methylpyrazole; its activity was insensitive to CO and not oxygen dependent, in contradistinction with that of the microsomal cytochrome P-450 and NADPH-dependent retinol oxidase. Chronic ethanol consumption resulted in an increased activity of the microsomal retinol dehydrogenase which may contribute to hepatic retinol depletion, especially in view of the insensitivity of the enzyme to ethanol inhibition.     

Effect of central adrenergic alpha receptor blockader IEM-611 on the activity of alcohol and aldehyde dehydrogenase in rat liver

The effect of IEM-611 (30 mg/kg) on alcohol consumption in rats under the conditions of voluntary choice between water and 15% ethanol was studied as that on alcohol dehydrogenase (ADH) in postmitochondrial supernatant and in NAD-dependent aldehyde dehydrogenases (A1DH) in liver mitochondria. Administration of IEM-611 during 6 or 12 days reduces ethanol consumption by 29 and 30%, respectively, activates ADH and appreciably decreases overall activity of NAD-dependent A1DH. At the same time the ADH/A1DH ratio increases. Activation of ADH and A1DH and the decreased ADH/A1DH ratio were disclosed in alcohol preferring rats as compared to water preferring animals. IEM-611 shifts enzymatic activity of ethanol metabolism towards the level characteristic for water preferring rats. It is suggested that variation of the ADH/A1DH ratio is one of the mechanisms responsible for the decreased ethanol consumption in rats.     

Exercise training with ageing protects against ethanol induced myocardial glutathione homeostasis

Glutathione plays a central role in the maintenance of cellular antioxidant defense. The alterations in the glutathione and associated recyclic enzymes caused by both exercise training and ethanol are well documented; however, their interactive effects with age are not well understood. Therefore, the influence of ageing and the interactive effects of exercise training and ethanol on the myocardial glutathione system in 3 months and 18 months old rats were examined. The results showed a significant (p<0.01) reduction in GSH content, Se and non-Se GSH-Px, GR and GST activities in the myocardium of rat with age. A significant increase (p<0.05) in the activities of these enzymes was observed in both age groups of rats in response to exercise training. This exercise-induced elevation of Se and non-Se GSH-Px and GR activities was more pronounced in the 18 months old rats when compared to 3 months old rats. Ethanol consumption significantly (p<0.05) reduced the GSH content, Se and non-Se GSH-Px and GR activities in both age groups of rats. In contrast, ethanol consumption significantly (p<0.05) increased the activity of GST. The combined action of exercise plus ethanol significantly (p<0.05) elevated the GSH content, Se and non-Se GSH-Px, GR and GST activities when compared to the ethanol treated rats in both age groups, indicating the suppression of ethanol-induced oxidative stress by exercise training. In conclusion, there was a compensatory myocardial response lessening ethanol-induced oxidative stress by exercise training, which seemed to result from the higher activity of glutathione recycling and utilizing enzymes, which may be critical for preventing chronic oxidative damage to the myocardium during ageing and even due to ethanol consumption.     

Modification of AlF-4- and receptor-stimulated phospholipase C activity by G-protein beta gamma subunits

Turkey erythrocyte membranes possess a phospholipase C that is markedly activated by P2Y-purinergic receptor agonists and guanine nucleotides. Reconstitution of [3H]inositol-labeled turkey erythrocyte membranes with guanine nucleotide regulatory protein (G-protein) beta gamma subunits resulted in inhibition of both AlF-4-stimulated adenylate cyclase and AlF-4-stimulated phospholipase C activities. The apparent potency (K0.5 approximately 1 microgram or 20 pmol of beta gamma/mg of membrane protein) of beta gamma subunits for inhibition of each enzyme activity was similar and occurred with beta gamma purified by different methodologies from turkey erythrocyte, bovine brain, or human placenta membranes. In contrast to the effect on AlF-4-stimulated activity, the stimulatory effect on phospholipase C of the P2Y-purinergic receptor agonist 2-methylthioadenosine 5'-triphosphate in the presence of guanine nucleotides was potentiated by 50-100% in a concentration-dependent manner by reconstitution of beta gamma subunits. beta gamma subunits did not affect the K0.5 value of 2-methylthioadenosine 5'-triphosphate for the stimulation of phospholipase C activity. These results indicate that beta gamma subunits influence phospholipase C activity in a concentration range similar to that necessary for regulation of adenylate cyclase activity and suggest the involvement of a G-protein possessing an alpha beta gamma heterotrimeric structure in coupling hormone receptors to phospholipase C.     

Alcohol motivation in rats under blockade of protein synthesis by cycloheximide

The influence of protein blocker cycloheximide on the ethanol intake in alcohol-dependent rats was studied. It was found that intracerebroventricular as well as perifornical area hypothalamus injection of cycloheximide caused inhibition of ethanol consumption in alcohol-dependent rats, persisting for 5-9 weeks. The blockade action of cycloheximide was more strong after its injection in phase of decreased ethanol intake. At the same time it was shown an increase in water and food intake. The blockade action of cycloheximide on ethanol intake was not found in alcohol-dependent rats. These data indicate that some protein substances take part in mechanisms of organization of alcohol motivation and dependence.     

Suppression of voluntary ethanol consumption in rats by gamma-butyrolactone

The effect of gamma-butyrolactone (GBL) on voluntary ethanol intake was studied in a group of Wistar rats in which a stable preference had been induced by exposure to increasing ethanol concentrations. These rats drank 60% of their daily fluid intake as 15% ethanol solution, corresponding to about 6 g ethanol/kg/day. GBL, injected intraperitoneally at the dose of 200 mg/kg, twice daily for 3 consecutive days, decreased ethanol intake by about 80% on the days of treatment, but did not reduce total fluid intake. Ethanol intake remained significantly reduced up to the 5th day following cessation of GBL administration. GBL, up to a concentration of 10(-3) M, inhibited neither alcohol-dehydrogenase nor aldehyde-dehydrogenase in rat liver homogenates, nor dopamine-beta-hydroxylase in homogenates of adrenal medulla or hypothalamus of rats. It is suggested that inhibition of firing in dopaminergic neurons mediates the suppressant effect of GBL on ethanol preference.     

Effects of the kappa opioid receptor antagonist MR-2266-BS on the acquisition of ethanol preference

Using a paradigm by which rats forced to drink a weak ethanol solution (2.5% w/v) (conditioning session) develop ethanol preference in consecutive retention testing days, the effects of the administration of the kappa opioid antagonist MR-2266-BS, prior to or after the forced ethanol session, were studied. Pre-conditioning subcutaneous (s.c.) administration of 1 mg/kg of MR-2266-BS induced a decrease in subsequent ethanol consumption without significantly modifying the acquisition of ethanol preference. Post-conditioning administration of MR-2266-BS (0.1, 1, 5 or 10 mg/kg) induced both a dose-dependent reduction in ethanol consumption and in preference throughout the three following days. The results of the present study provide further support of the involvement of kappa-type opioids on drinking behavior, and suggest that kappa receptors may be involved in the consumption and development of preference to ethanol.     

Redox potential dependence of photophosphorylation and electron transfer in continuous illumination of Rhodopseudomonas sphaeroides chromatophores

The rate of ethanol elimination in fed and fasted rats can be predicted based on the liver content of alcohol dehydrogenase (EC 1.1.1.1), the steady-state rate equation, and the concentrations of substrates and products in liver during ethanol metabolism. The specific activity, kinetic constants, and multiplicity of enzyme forms are similar in fed and fasted rats, although the liver content of alcohol dehydrogenase falls 40% with fasting. The two major forms of the enzyme were separated and found to have very similar kinetic properties. The rat alcohol dehydrogenase is subject to substrate inhibition by ethanol at concentrations above 10 mM and follows a Theorell-Chance mechanism. The steady-state rate equation for this mechanism predicts that the in vivo activity of the enzyme is limited by NADH product inhibition at low ethanol concentrations and by both NADH inhibition and substrate inhibition at high ethanol concentrations. When the steady-state rate equation and the measured concentrations of substrates and products in freeze-clamped liver of fed and fasted rats metabolizing alcohol are employed to calculate alcohol oxidation rates, the values agree very well with the actual rates of ethanol elimination determined in vivo.     

The effect of Hoe-427 (an ACTH4-9 analog) on free-choice ethanol consumption in male and female rats.

Ethanol consummatory patterns of individual male and female rats and the effects of Hoe-427 (Ebiratide), an ACTH4-9 analog, thereon, were studied in a test system using 24 hour, two-bottle free choice consumption between 0.2% saccharin and 10% ethanol in 0.2% saccharin. Single, daily i.p. doses (0.03mg/rat) of either ACTH4-10 or its analog resulted in a significant reduction of daily ethanol consumption with no effects on saccharin consumption. After 4 days of treatment, male rats consistently exhibited a rebound increase in ethanol consumption; this effect was not seen in females. The daily ethanol consummatory patterns of the female animals seemed to exhibit a 4-6 day cyclic rhythymicity, suggesting an interaction with estrous cycles. These results support a role for ACTH4-10 in the initiation of ethanol consummatory behavior in rats and suggests the existence of sex differences in this phenomenon.     

Pancreatic regeneration after chronic ethanol feeding in rats.

Increase of phosphatidic acid (PA) accumulation in response to caerulein (Cae) and after subtotal pancreatectomy (SP) has been previously described and phospholipase D (PLD) derived PA involvement in pancreatic regeneration was suggested. We also described decrease of Cae stimulated PA accumulation after a single dose of ethanol (both in vitro and in vivo). The present study was undertaken in order to determine the influence of chronic ethanol feeding on basal and Cae stimulated PA accumulation and other parameters of pancreatic regeneration in control and ethanol feed rats. Male rats were pair fed ad libitum with an isocaloric liquid diet (Lieber De Carli) with or without ethanol. In vitro study: pair fed rats were killed after 2 or 6 weeks of feeding, pancreata were dissected out and weighted, dispersed pancreatic acini were then prepared and loaded with 3H myristic acid in order to label the phosphatidylcholine pool. Phosphatidic acid (3H PA) accumulation, in the presence of propranolol, was measured after stimulation with increasing doses of Cae. In vivo study: PA was measured 3 days after SP or sham operation in both groups of rats, and also after 1 h of Cae infusion (0.25 microg/kg/h). Pancreatic weight, amylase, protein, RNA and DNA content were established. Results: In vitro study 1) Basal PLD activity expressed as PA accumulation was significantly elevated after 6 weeks of ethanol feeding in comparison to the control values (28%). 2) Cae in doses ranging from 100 pM to 5 nM was not able to stimulate PA accumulation in isolated pancreatic acini prepared from ethanol fed rats. In vivo study: 1) Body weight and pancreatic weight were similar in, both the ethanol fed and the control groups, after 2 and 6 weeks. 2) Ethanol feeding significantly decreased total amylase content in the pancreas, but did not change protein, RNA and DNA content. 3) in contrast to the control animals in which SP caused a 71.1% increase of PA accumulation over the sham operation, subtotal pancreatectomy was not able to stimulate PA in rats fed with ethanol. 4) Also Cae infusion did not stimulate PA accumulation in the ethanol fed animals in comparison to the controls. Since the involvement of PLD activation in the early stages of pancreatic regeneration was postulated, our results suggest that chronic ethanol feeding can influence this process by decrease of PA production, probably because of the inhibition of hydrolytic PLD activity in the presence of ethanol. This could be one of the mechanisms responsible for pancreatic injury after chronic ethanol consumption.