Jadwiga Zalewska-Kaszubska

Effect of acute administration of ethanol on beta-endorphin plasma level in ethanol preferring and non-preferring rats chronically treated with naltrexone.

An ample support can be found in professional literature for the hypothesis that the endogenous opioid system plays an important role in developing a craving for alcohol. It is well established that people with a genetic deficit of beta-endorphin are particularly susceptible to alcoholism. In our study, we looked into the beta-endorphin plasma level of animals with high- and low-risk of alcohol dependency after repeated treatment with naltrexone, the opioid antagonist known to be effective in the treatment of alcoholism. We used the Warsaw High Preferring (WHP) and Warsaw Low Preferring (WLP) rats and treated them for 10 days with naltrexone in a dose of 2 mg/kg i.p. One hour before blood collection the rats were injected with a single dose of ethanol. A prolonged naltrexone treatment or a single application of ethanol resulted in the increase of the beta-endorphin plasma level. In the WLP rats repeated naltrexone treatment prevents the ethanol-induced increase in beta-endorphin plasma level. In the WHP rats the level of this peptide was similar to it while they were undergoing the naltrexone treatment or had received a single alcohol injection. This finding supports the proposition that the endogenous opioid system plays an important role in developing a craving for alcohol. It is likely that effectiveness of naltrexone in reducing craving for alcohol results from the attenuation of the rewarding properties of ethanol and restoring the beta-endorphin deficit in reward system.

Deficit in beta-endorphin peptide and tendency to alcohol abuse.

Human and animal studies suggest that there is a correlation between endogenous opioid peptides, especially beta-endorphin, and alcohol abuse. It has been proven that the consumption of alcohol activates the endogenous opioid system. Consumption of alcohol results in an increase in beta-endorphin level in those regions of the human brain, which are associated with a reward system. However, it has also been observed that habitual alcohol consumption leads to a beta-endorphin deficiency. It is a well-documented phenomenon that people with a genetic deficit of beta-endorphin peptide are particularly susceptible to alcoholism. The plasma level of beta-endorphin in subjects genetically at high risk of excessive alcohol consumption shows lower basal activity of this peptide. Its release increases significantly after alcohol consumption. Clinical and laboratory studies confirm that certain genetically determined factors might increase the individuals vulnerability to alcohol abuse.

Effect of chronic acamprosate treatment on voluntary alcohol intake and β-endorphin plasma levels in rats selectively bred for high alcohol preference

Our previous studies have shown that repeated acamprosate administration to ethanol-naive Warsaw high preferring (WHP) rats resulted in increased plasma beta-endorphin levels and at least partially prevents increases in levels of this peptide after a single administration of ethanol compared with untreated control rats. The objective of the present study, which included 45 WHP rats, was to continue the past research and investigate the effect of 10-day acamprosate treatment (200 mg/kg p.o.) on alcohol intake using a free-choice procedure and on changes in plasma beta-endorphin levels while alcohol is available, and 10 days after alcohol withdrawal. Voluntary alcohol consumption increases plasma levels of beta-endorphin from 440+/-25 pg/ml to 711+/-57 pg/ml (p=0.0002). After a 10-day of alcohol withdrawal, the levels of this peptide were significantly reduced compared with levels in rats with free access to ethanol (711+/-57 pg/ml vs. 294+/-38 pg/ml, p=0.000001) and in control naive rats (440+/-25pg/ml vs. 294+/-38pg/ml, p=0.044). Chronic treatment with acamprosate increased plasma beta-endorphin levels both in WHP rats with free access to ethanol (440+/-25 pg/ml vs. 616+/-49 pg/ml, p=0.008) and in rats after ethanol withdrawal (440+/-25 pg/ml vs. 620+/-56 pg/ml, p=0.007). In the group with free access to ethanol, there was a significant reduction in mean ethanol intake, from 6.75+/-0.20 g/kg body weight/day to 4.68+/-0.25 g/kg/day. Our results indicate that chronic acamprosate treatment may have beneficial effects, as it increases the beta-endorphin concentration thereby compensating for beta-endorphin deficiency during ethanol withdrawal. As the endogenous opioid system has an important role in the development of craving for alcohol, restoring the alcohol-induced deficits in beta-endorphin levels may be an important factor to prevent craving and maintaining abstinence. We suppose that the anti-craving mechanism of acamprosate that has been reported to abolish excessive glutamate release during alcohol withdrawal may be accompanied by compensation for the beta-endorphin deficiency.

Changes in the beta-endorphin plasma level after repeated treatment with acamprosate in rats selectively bred for high and low alcohol preference

The aim of this study was to evaluate the beta-endorphin (beta-endorphin) plasma level in Warsaw Low Preferring (WLP) and Warsaw high-preferring (WHP) rats after repeated administration of acamprosate, one of most effective drug in the treatment of alcoholism. Treatment with acamprosate in dose 200mg/kg, p.o. for 10 days induced an increase in plasma beta-endorphin levels. A single injection of ethanol also results in the increase of beta-endorphin level. Moreover, it was found that single injection of ethanol to WHP rats resulted in lower increase of plasma beta-endorphin content in rats earlier treated with acamprosate. In WLP rats, repeated acamprosate treatment prevents the ethanol-induced increase in plasma beta-endorphin level. It may be concluded that acamprosate modulates the endogenous opioid system.

Voluntary alcohol consumption and plasma beta-endorphin levels in alcohol preferring rats chronically treated with levetiracetam: a preliminary study.

Many recent researches have confirmed the effectiveness of antiepileptic drugs in preventing alcohol dependency, whereas our previous study showed that repeated treatment with topiramate, a new antiepileptic drug, was effective in increasing the plasma levels of beta-endorphin (an endogenous opioid peptide) in rats. It is well documented that in humans a genetic deficit of beta-endorphin is often associated with alcohol addiction as alcohol consumption elevates the level of this peptide. The aim of the present study is multifaceted: to investigate the effect of repeated treatment of levetiracetam (50 or 100mg/kg b.w., twice daily) on voluntary alcohol intake in alcohol preferring rats (Warsaw High Preferring; WHP) and to assess changes in plasma beta-endorphin levels while alcohol is available and when it is not available for an extended period of time. We observed a noticeable increase in the levels of beta-endorphin in rats with free access to alcohol whether in a prolonged levetiracetam-treated or vehicle-treated group. However, in the levetiracetam group, a voluntary intake of alcohol diminished in comparison with both the pretreatment period and in comparison with the vehicle-treated rats. A similar increase in the plasma beta-endorphin levels was observed in levetiracetam-treated rats that did not have access to ethanol. This finding lets us to believe that levetiracetam may be a promising medication in treatment of alcohol dependency as its application leads to the increase in the beta-endorphin concentration and ultimately results in reducing deficiency of this peptide.

Effect of repeated treatment with topiramate on the beta-endorphin plasma level in rats selectively bred for high and low alcohol preference

Recent research indicates that topiramate has a role in the treatment of alcohol dependence. Topiramate has multiple mechanisms of action including enhancement of GABA-ergic inhibitory transmission and blocking excitatory glutamate neurotransmission, and modulating voltage-gated sodium and calcium ion channels and inhibiting carbonic anhydrase. In this study, we examined the effect of topiramate on endogenous opioid systems, which have an important role in the development of alcohol dependence. We investigated the beta-endorphin plasma level of animals with high- and low-risks of alcohol dependency after repeated treatment with topiramate. We used the Warsaw High Preferring (WHP) and Warsaw Low Preferring (WLP) rats, and treated them with topiramate at a dose of 80 mg/kg p.o. for 14 days. In WHP rats treatment with topiramate led to an increase in beta-endorphin plasma levels, which persisted at the same level even after a single injection of alcohol. The level of this peptide with topiramate was lower than in alcohol-injected WHP rats who did not receive topiramate. Beta-endorphin levels in WHP rats after topiramate or topiramate and ethanol treatment were similar to the basal level of this peptide in WLP rats. In WLP rats, topiramate did not prevent the ethanol-induced increase in beta-endorphin plasma level. We propose that administration of topiramate may have different effects on the opioid system involved in dependence according to genetic susceptibilities to alcoholism.