Cannabinoid-serotonin interactions in alcohol-preferring vs. alcohol-avoiding mice.

Because cannabinoid and serotonin (5-HT) systems have been proposed to play an important role in drug craving, we investigated whether cannabinoid 1 (CB1) and 5-HT(1A) receptor ligands could affect voluntary alcohol intake in two mouse strains, C57BL/6 J and DBA/2 J, with marked differences in native alcohol preference. When offered progressively (3-10% ethanol) in drinking water, in a free-choice procedure, alcohol intake was markedly lower (approximately 70%) in DBA/2 J than in C57BL/6 J mice. In DBA/2 J mice, chronic treatment with the cannabinoid receptor agonist WIN 55,212-2 increased alcohol intake. WIN 55,212-2 effect was prevented by concomitant, chronic CB1 receptor blockade by rimonabant or chronic 5-HT(1A) receptor stimulation by 8-hydroxy-2-(di-n-propylamino)-tetralin, which, on their own, did not affect alcohol intake. In C57BL/6 J mice, chronic treatment with WIN 55,212-2 had no effect but chronic CB1 receptor blockade or chronic 5-HT(1A) receptor stimulation significantly decreased alcohol intake. Parallel autoradiographic investigations showed that chronic treatment with WIN 55,212-2 significantly decreased 5-HT(1A)-mediated [35S]guanosine triphosphate-gamma-S binding in the hippocampus of both mouse strains. Conversely, chronic rimonabant increased this binding in C57BL/6 J mice. These results show that cannabinoid neurotransmission can exert a permissive control on alcohol intake, possibly through CB1-5-HT(1A) interactions. However, the differences between C57BL/6 J and DBA/2 J mice indicate that such modulations of alcohol intake are under genetic control.

The effects of acetaldehyde in vitro on proteasome activities and its potential involvement after alcoholization of rats by inhalation of ethanol vapours.

BACKGROUND/AIMS: Some models of chronic ethanol administration resulted in decreased proteasome activities. The mechanisms still remain speculative. In the present study, we tested another model of alcoholization with high blood alcohol levels (BALs) and high acetaldehyde fluxes as well as the in vitro effect of acetaldehyde on proteasome. Methods/ RESULTS: Ethanol vapour chronically inhaled by adult Wistar rats up to a specific protocol, can reach high BALs (200 mg/dl) with significant circulating acetaldehyde levels. After 4 weeks of ethanol intoxication, although cytochrome CYP2E1 was increased, liver lipid peroxidation remained unchanged when protein carbonyls augmented selectively for high molecular weight with a decrease of the proteasome activities in ethanol rats. Several aldehydes inhibit proteasome function; we specifically explored the effects of acetaldehyde, the first alcohol metabolite. Adduction of acetaldehyde in vitro to cytosolic proteins inhibits proteasome in a dose-dependent manner. Acetaldehyde adducted to purified proteasome also exhibits a decrease in its activities. Furthermore, an acetaldehyde-adducted protein, i.e. bovine serum albumin (BSA) is less degraded than a native BSA by purified proteasome. These findings suggest that acetaldehyde, if overproduced, can inhibit proteasome activities and reduce the proteolysis of acetaldehyde-adducted proteins. CONCLUSIONS: Our study, for the first time, provided the evidence that acetaldehyde by itself inhibits proteasome activities. As the chronic inhalation model used in this study is not associated with an overt lipid peroxidation, one can suggest that high BALs and their subsequent high acetaldehyde fluxes contribute to impairment of proteasome function and accumulation of carbonylated proteins. This early phenomenon may have relevance in experimental alcohol liver disease.

Genetics of behaviour: phenotypic and molecular study of rats derived from high- and low-alcohol consuming lines.

The aim of this study was to analyse the genetic basis of excessive ethanol consumption and its relationship with emotional reactivity. The high-ethanol preferring line of rats used is characterized by a: (i) high voluntary consumption of alcohol; (ii) high sensitivity to taste reinforcement (saccharine, quinine); (iii) high locomotor activity in a novel environment; and (iv) low emotional reactivity, these features being opposite in the Wistar-Kyoto (WKY) rat strain. The F2 population demonstrated a very large variability in these behavioural traits, and factor analysis revealed that these characteristics appear to be largely unrelated to each other. The molecular bases for these differences were investigated by quantitative trait loci (QTL) analysis. For this purpose, the 196 F2 rats were genotyped with regularly distributed markers on the whole genome, and genetic linkage maps were generated for all subsequent QTL analyses. A locus with a maximum LOD score of 7.6 and accounting for approximately 61% of the genetic variance of the trait in the F2 population was detected on chromosome 4 for alcohol drinking. In the same region, we found a QTL related to the reinforcement properties of saccharin, with a significant LOD score of 4.9 and explaining 46% of the variance of the trait. Other significant QTL were found for plus maze behaviour and open field activity on chromosome 1. Current research aims to identify the gene(s) involved.

Chronic ethanol exposure differentially regulates NOS1 mRNA levels depending on rat brain area.

Several works have suggested a potential role for nitric oxide in alcohol-seeking behavior and we have recently shown that the specific blockade of the expression of the neuronal nitric oxide synthase (NOS1) decreases rat ethanol intake. Our previous results have also shown that chronic ethanol exposure has differential effect on the brain NOS activity depending on rat brain area. In the present study, we examine the effects of chronic administration of ethanol on the NOS1-mRNA levels measured with the competitive reverse transcriptase-polymerase chain reaction technique. Chronic administration of ethanol differentially regulated NOS1-mRNA levels depending on rat brain area. Chronic ethanol exposure had no effect on the NOS1-mRNA levels in frontal cortex, but decreased the NOS1-mRNA levels in hippocampus (P<0.01, 39% decrease) and induced a strong increase in striatum (P<0.01, 92% increase). These effects of ethanol were not affected by 7-nitro indazole (25 mg/kg, i.p. daily for 1 week) treatment. These data further support that NOS1 is regulated by chronic exposure to ethanol and that these effects are related to modifications of mRNA levels.

Bile salts modulate chronic ethanol-induced hepatotoxicity.

This study tested the hypothesis that chronic ethanol-induced injury in rats may be modified by the hydrophobicity of the bile acid pool. The supplementation to chronic ethanol feeding (28 days) with chenodeoxycholate, a hydrophobic bile salt, aggravated steatosis (accumulation of triacylglycerols and cholesterol esters), lipoperoxidation and cytolysis (expressed as elevations of activities of aspartate aminotransferase and glutamate dehydrogenase), while the addition of ursodeoxycholic acid, a hydrophilic bile salt, alleviated ethanol-induced hepatic alterations. Furthermore, our data show that ursodeoxycholic acid still exerts its beneficial effects in a model of more severe hepatic intoxication induced by the co-administration of ethanol and chenodeoxycholic acid. The hepato-protective effect observed appears to be independent of the choleretic properties of ursodeoxycholic acid and may be due partly to the capacity of the bile acid to preserve mitochondria.