Diet composition, alcohol utilization, and dependence

Orexin-mediated motivated arousal and reward seeking

The neuromodulator orexin has been identified as a key factor for motivated arousal including recent evidence that sleep deprivation-induced enhancement of reward behavior is modulated by orexin. While orexin is not necessary for either reward or arousal behavior, orexin neurons' broad projections, ability to sense the internal state of the animal, and high plasticity of signaling in response to natural rewards and drugs of abuse may underlie heightened drug seeking, particularly in a subset of highly motivated reward seekers. As such, orexin receptor antagonists have gained deserved attention for putative use in addiction treatments. Ongoing and future clinical trials are expected to identify individuals most likely to benefit from orexin receptor antagonist treatment to promote abstinence, such as those with concurrent sleep disorders or high craving, while attention to methodological considerations will aid interpretation of the numerous preclinical studies investigating disparate aspects of the role of orexin in reward and arousal.

The effects of ethanol on diverse components of choice in the rat: reward discrimination, preference and relative valuation

Alcohol consumption impairs judgment and choice. How alcohol alters these crucial processes is primarily unknown. Choice can be fractionated into different components including reward discrimination, preference and relative valuation that can function together or in isolation depending upon diverse factors including choice context. We examined the diverse components and contextual effects by analyzing the effects of alcohol drinking on choice behavior in a task with a reduced level of temporal and spatial constraints. Rats were trained to drink 10% ethanol during 6 weeks of behavior testing using a combined sucrose-fade and two-bottle free-choice procedure. Two different sucrose pellet outcomes (e.g., constant vs. variable) were presented each week to examine the impact of voluntary drinking on reward-based decision-making. Behavioral contexts of single option, free choice and extinction were examined for each outcome set. Comparisons were made between alcohol and control groups and within the alcohol group over time to inspect choice profiles. Between-group results showed alcohol drinking animals expressed altered place preference and modified sucrose reward approach latencies. The within-group profile showed that alcohol drinking animals can express adequate reward discrimination, preference and incentive contrast during free choice. All of these components were significantly reduced during the context of extinction. Control animals were also impacted by extinction but not as severely. The findings point to a need for a greater focus on the context and the diverse components of choice when examining external and internal factors influencing decision-making during alcohol or other substance of abuse exposure.

Different molecular mechanisms underlie ethanol-induced bone loss in cycling and pregnant rats

Chronic ethanol (EtOH) consumption can result in osteopenia. In the current study, we examined the modulation of EtOH-induced bone loss during pregnancy. Nonpregnant and pregnant dams were intragastrically infused either control or EtOH-containing diets throughout gestation (gestation d 5 through 20 or an equivalent period of 15 d) by total enteral nutrition. The effects of EtOH (8.5 to 14 g/kg/d) on tibial bone mineral density (BMD), mineral content (BMC), and bone mineral area were assessed at gestation d 20 via peripheral quantitative computerized tomography. EtOH caused a dose-dependent decrease in BMD and BMC without affecting bone mineral area. Trabecular BMD and BMC were significantly lower in EtOH-treated, nonpregnant dams, compared with pregnant cohorts at the same infused dose of EtOH and urinary ethanol concentrations. Static histomorphometric analysis of tibiae from pregnant rats after EtOH treatment showed decreased osteoblast and osteoid surface, indicating inhibited bone formation, whereas EtOH-treated cycling rats showed higher osteoclast and eroded surface, indicative of increased bone resorption. Circulating osteocalcin and 1,25-dihydroxyvitamin D3 were lower in both EtOH-fed nonpregnant and pregnant rats. Gene expression of osteoclast markers, 70 kDa v-ATPase, and tartrate-resistant acid phosphatase were increased selectively in nonpregnant EtOH-treated rats but not pregnant rats. Moreover, only nonpregnant EtOH-fed rats showed induction in bone marrow receptor activator of nuclear factor-kappaB ligand mRNA and decreased circulating 17beta-estradiol levels. Our data suggest that EtOH-induced bone loss in pregnant rats is mainly due to inhibited bone formation, whereas in nonpregnant rats, the data are consistent with increased osteoclast activation and bone resorption concomitant with decreased estradiol levels.

Liver fat and plasma ethanol are sharply lower in rats fed ethanol in conjunction with high carbohydrate compared with high fat diets

The effects of high fat and high carbohydrate diets on alcohol metabolism were studied on blood alcohol and liver fat concentration. In Experiment 1, rats consumed an alcohol-containing liquid diet. Blood was collected for ethanol, glucose and lactate analyses and livers were excised for lipid determination. Blood ethanol and liver fat were lower when rats consumed the high carbohydrate diet. Glucose concentrations were lower in rats fed the high fat diet compared with those fed the high carbohydrate diet when ethanol was consumed. In Experiment 2, rats consumed a high fat, ethanol-containing diet for 13 d. Half of the rats were switched to a high carbohydrate, ethanol-containing diet for an additional 11 d. The same analyses were carried out as for Experiment 1. Switching the high fat-fed rats to the high carbohydrate diet reversed the high blood ethanol and high liver fat values, even though the rats consumed significantly more alcohol with the high carbohydrate diet. In Experiment 3 the same high fat and high carbohydrate diets without ethanol were consumed for 2 wk, at which time ethanol was administered acutely, intraperitoneally, at 2 g/kg. Blood was analyzed for ethanol, glucose and lactate 30, 60 and 120 min after injection. Rats fed the high carbohydrate diet had lower blood ethanol but higher lactate at 120 min compared with those fed the high fat diet. The results suggest that the rate of ethanol elimination is slower in rats fed high fat than in those fed high carbohydrate diets, resulting in elevated blood ethanol and liver fat levels for the former.

Monoaminergic changes associated with audiogenic seizures in ethanol-dependent rats

1. A previous report demonstrated the efficacy of combining dopaminergic and serotonergic agonists in suppressing audiogenic seizures induced in ethanol-dependent rats undergoing withdrawal. Moreover, an increase in dopamine and a reduction in serotonin levels in the striatum were associated with such seizures. 2. The present study was designed to examine neurochemical changes in the striatum associated with repeated episodes of ethanol withdrawal seizures in untreated ethanol-dependent rats as well as in those treated with amphetamine and fenfluramine in combination. 3. Ethanol-dependent rats undergoing audiogenic seizures exhibited an increase in striatal dopamine and a reduction in striatal serotonin as compared to control and ethanol-dependent rats not undergoing seizures. Amphetamine and fenfluramine in combination effectively suppressed the audiogenic seizures by reversing the neurochemical changes in the striatum in ethanol-dependent rats. However, increased dopamine but decreased serotonin levels in the striatum were observed in rats undergoing one episode of ethanol withdrawal, but not in those experiencing multiple episodes of ethanol withdrawal. 4. Thus, alterations in striatal dopamine and serotonin levels were, at best, necessary but not sufficient to predispose audiogenic seizure susceptibility in ethanol-dependent rats.

Effects of phentermine and fenfluramine on alcohol consumption and alcohol withdrawal seizures in rats

The drug combination of phentermine plus fenfluramine has been used clinically in both the treatment of obesity and alcoholism. The aim of the current study was to assess the interaction of the two drugs on consumption of both an alcohol-containing and a nonalcoholic diet. Furthermore, the efficacy of the drug combination on suppression of withdrawal seizures was determined. Animals were either maintained on a 6% alcohol-containing diet, free-fed an isocaloric control, or pair-fed the control diet. It was observed that, with regard to body weight growth curves, alcohol provides about 2.5 kcal/g. Both phentermine and fenfluramine caused a decrease in consumption 1 h after administration; however, during the next 23 h, 4 mg/kg phentermine significantly increased consumption of all diets. At doses of 1 and 2 mg/kg, fenfluramine selectively reduced consumption of the alcohol-containing diet as compared to the isocaloric diets. Lower doses of fenfluramine blocked the increases in consumption induced by phentermine. Furthermore, in animals fed the nonalcoholic diet, the drug combination of 2 mg/kg fenfluramine plus 8 mg/kg phentermine produced a 63-82% reduction in consumption, an effect not seen when either drug was administered alone. This greater than additive effect was also seen in the earlier time periods in animals pair-fed the control diet. Neurochemical analysis from these animals revealed that the alcohol-dependent animals displayed a significant reduction of DOPAC and 5-HIAA levels in the striatum, frontal cortex, and hypothalamus after a 9-h withdrawal period, further implicating the serotonergic and dopaminergic systems in mediation of withdrawal symptoms and alcohol craving. Finally, 8 mg/kg phentermine plus 8 mg/kg fenfluramine completely abolished alcohol withdrawal seizures, compared to a 78% rate in saline treated rats. In conclusion, the coadministration of phentermine plus fenfluramine produced a moderate reduction of alcohol consumption and was completely effective at reducing alcohol withdrawal seizures.

Alcohol utilization and dependence with special reference to protein level in a liquid diet for rats

Experiments were carried out with a nutritionally balanced diet to test the response of rats to levels of ethanol between 0% and 6%, and to different levels and sources of protein and amino acid supplements in relation to alcohol utilization and withdrawal seizures. The high-calorie/high-carbohydrate liquid diet was well tolerated when the alcohol level was less than 30% of total calories, or 4.5% of diet. When alcohol was provided at 6% of diet, or 33% of total calories, growth and withdrawal seizure rates were negatively affected in comparison with the lower ethanol levels, even though ethanol consumption (in g/kg/day) was not different. The 6% alcohol diet was then altered through the addition of more protein calories, from 13% to 20%. This supplementation improved growth rate of the animals and reduced the rate of withdrawal seizures. The improvement from the additional protein was observed with both casein and soy protein, and was not attributable to any one or even several amino acids that might serve as transmitter precursors. A mixture of all essential amino acids representing the difference in amino acids between 13% and 20% casein protein calories was an effective as the equivalent amount of intact protein. The nonessential amino acids equivalent to 7% casein protein calories, when added to the 13% protein calories diet, increased the rate of withdrawal seizures, presumably by exacerbating the protein deficiency in the 13% protein diet. It was concluded that a 1000-1200 kcal/kg diet with 20% kcal from protein and 50% kcal from carbohydrate provides an optimal nutrient balance for efficient utilization of a 6% ethanol liquid diet for rats.