Administration of the 5-HT2C receptor antagonist SB-242084 into the nucleus accumbens blocks the expression of ethanol-induced behavioral sensitization in Albino Swiss mice.

Behavioral sensitization to the stimulating effect of ethanol (EtOH) or other drugs, which can be observed in mice as an increase in locomotor activity after repeated administration, has been associated with neuroadaptations within the dopaminergic mesolimbic pathway. In the nucleus accumbens (NAc), an afferent region of the mesolimbic pathway, dopamine (DA) release can be modulated by serotonergic 2C receptors (5-HT2CR). The aim of the present study was to evaluate the function of 5-HT2CR in the expression of EtOH-induced behavioral sensitization in Albino Swiss mice with various levels of sensitization to EtOH. In the four experiments that we performed, the mice were given saline or 2.2 g/kg EtOH daily for 21 days. Based on their locomotion on day 21, the EtOH-pretreated mice were assigned to one of two groups, highly sensitized or weakly sensitized to the stimulating effect of EtOH. In each experiment, 2 weeks after the 21-day treatment (withdrawal period), the mice were submitted to four pharmacological challenges of two drug treatments each. The mice in experiments 1 and 2 received two i.p. injections, whereas the mice in experiments 3 and 4 received an intra-NAc administration followed by an i.p. injection. The challenges were: saline+saline; saline+EtOH; SB-242084 (a 5-HT2CR antagonist; 0.5, 1.0 or 2.0 mg/kg i.p. or 1.0 or 2.0 µg/side intra-NAc)+EtOH; and SB-242084 (0.5, 1.0 or 2.0 mg/kg i.p. or 1.0 or 2.0 µg/side intra-NAc)+saline. At all tested doses, i.p. administration of SB-242084 did not affect the stimulating effect of EtOH in the highly sensitized mice. However, when delivered by intra-NAc administration, SB-242084 reduced (at 1.0 µg/side) or completely blocked (at 2.0 µg/side) the expression of EtOH-induced behavioral sensitization in the highly sensitized mice. These findings suggest that the expression of behavioral sensitization to the stimulating effect of EtOH depends on accumbal 5-HT2CR activity.

Morphine attenuates the expression of sensitization to ethanol, but opioid antagonists do not.

Behavioral sensitization to ethanol is characterized by an increased locomotor activity after repeated exposure. A great variability exists among species and strains in the development of sensitization. There is a growing amount of evidence to indicate that the opioid system is involved in alcoholism; it is possible, therefore, that this system also modulates the sensitization to ethanol. In this study we evaluated the role of the opioid system in determining the variability of the sensitized response to ethanol. Mice received repeated administrations of ethanol (2.2 g/kg) or saline every other day for 10 days. According to their locomotor response on the last day of treatment, ethanol-treated animals were classified into two groups: sensitized or non-sensitized mice. After the treatment, mice were submitted to four challenges 48 h apart. In experiments 1 and 2, mice were challenged, respectively, with i.p. administration of opioid antagonists (naloxone or naltrexone) or an opioid agonist (morphine), followed immediately by 2.2 g/kg ethanol. In experiment 3, animals received morphine by i.c.v., followed by 2.2 g/kg of ethanol (i.p.). Pretreatment with opioid antagonists (naloxone or naltrexone) did not block the expression of ethanol sensitization; however pretreatment with morphine attenuated the increased locomotor activity after ethanol administration in sensitized mice. In experiment 4, after the ethanol or saline treatment, mice brains were processed and brain mu opioid binding was assessed by autoradiography using [3H]D-Ala2,N-mePhe4, Gly-ol5-enkephalin ([3H]DAMGO). No differences were seen between any of the groups of mice, so the agonist effect is not likely to be mediated by differences in binding to mu opioid receptors.

Is behavioral sensitization to ethanol associated with contextual conditioning in mice?

Behavioral sensitization to drugs of abuse seems to involve learning processes. In mice, ethanol-induced locomotor sensitization is potentiated by repeated pairing of ethanol (EtOH) injections and the testing chamber. The present study aimed to test: (1). the association between the performance in a contextual conditioning task and the development of behavioral sensitization to EtOH in mice; (2). whether EtOH sensitization would be expressed in a different testing environment. Male albino Swiss mice (n=72) were initially submitted to a contextual fear conditioning task. After 2 weeks without manipulation, the animals received daily i.p. injections of 2.2 g/kg EtOH (n=52) or saline (n=20), for 21 days. They were tested weekly for locomotor activity in activity cages. After 1 week of withdrawal, all mice received 2.2 g/kg EtOH and had their locomotor activity recorded in an open-field. According to the locomotor behavior displayed along the 21-day treatment, EtOH-treated mice were classified as sensitized (n=15) or non-sensitized (n=15). When these subgroups and saline-treated mice were compared for the freezing response in the conditioning test, sensitized mice displayed a greater freezing time than non-sensitized mice. When challenged with EtOH in the open-field, none of the EtOH-treated subgroups expressed behavioral sensitization. These results suggest that the development of EtOH sensitization seems to be positively associated with contextual learning, and further confirms that the expression of sensitization is highly dependent on contextual cues.

Biological markers of alcohol consumption in nondrinkers, drinkers, and alcohol-dependent Brazilian patients.

BACKGROUND: The purpose of this study was to compare the sensitivity and specificity of some new and traditional biological markers and indicators of health among Brazilian nondrinkers, drinkers, and alcohol-dependent patients. MATERIAL AND METHODS: We evaluated 130 nondrinkers, 167 drinkers, and 183 alcohol-dependent drinkers from Brazil who participated in the WHO/ISBRA Study on State and Trait Markers of Alcohol Use and Dependence. A standardized WHO/ISBRA Interview Schedule provided background information on the subjects' characteristics including reported health problems and alcohol consumption. Blood samples were analyzed for aspartate aminotransferase (AST), carbohydrate deficient transferrin (CDT), gamma-glutamyltransferase (GGT), blood alcohol levels (BAL), and platelet adenylate cyclase activity (basal levels [AC] and levels after stimulation with Gpp(NH)p, cesium fluoride, and forskolin). RESULTS: The alcohol-dependent drinkers presented higher levels of AST, GGT, AC, CDT, and BAL than the nondrinkers and drinkers, whose levels were similar. Sex differences in the sensitivity of CDT and AC were found. The alcohol-dependent women presented a lower prevalence of abnormal values of CDT and Gpp(NH)p-stimulated AC than the alcohol-dependent men, despite the fact that they presented similar alcohol consumption levels. The alcohol-dependent drinkers presented a higher prevalence of clinical disorders than the nondrinkers and drinkers. The drinkers and alcohol-dependent patients presented significantly higher rates of gastritis than the nondrinkers. CONCLUSIONS: Sex differences in the sensitivity of CDT and AC suggest that these markers are not as sensitive at detecting excessive alcohol use in women as they are in men. If data from this Brazilian sample are compared with those reported for international samples, relevant differences are detected, which suggests that genetic and cultural differences should be considered in the selection of biological markers of heavy alcohol consumption.

Does the increase in locomotion induced by ethanol indicate its stimulant or anxiolytic properties?

The responses of mice to low doses of acutely and chronically administered ethanol (2.0 g/kg) and diazepam (2.0 mg/kg) were observed in activity cages, the open field and the elevated plus-maze. After prolonged administration, ethanol significantly increased locomotion in the activity cages and the plus-maze. In the open field, an increase was only observed in the tests performed after 7 and 14 days of treatment. Ethanol increased the open-arm time in the plus-maze in all the tests, including after acute administration, suggesting an anxiolytic effect. Diazepam induced an anxiolytic effect after 14 days of daily injections but had no stimulant effect on locomotion. Moreover, after prolonged administration sensitization to the anxiolytic, but not to the stimulant effect, was observed. In short, the present paper's data support the hypothesis that the stimulant and anxiolytic effects of ethanol are probably being mediated by distinct mechanisms. Furthermore, these data support the hypothesis that drugs that lead to abusive use, such as ethanol, may act both as positive and negative reinforcement.

Sensitization to ethanol's stimulant effect is associated with region-specific increases in brain D2 receptor binding.

RATIONALE: Stimulation of locomotor activity by low doses of ethanol (EtOH) and the potentiation of this response after repeated administration (sensitization) have been related to EtOH's rewarding and addictive properties and to altered dopaminergic activity in brain. In mice, behavioral sensitization to EtOH occurs only in a subset of treated animals, and this provides an opportunity for distinguishing general drug effects from sensitization-specific brain effects. OBJECTIVES: In view of evidence suggesting a role for dopamine D2 receptors in EtOH preference and abuse liability, the present study addressed the hypothesis that D2 binding would be altered in specific brain regions in mice showing differential sensitization responses to chronic EtOH administration. METHODS: Male albino Swiss mice received 2.4 g/kg EtOH i.p. daily for 21 days and were then separated into sensitized or non-sensitized subgroups on the basis of weekly locomotor activity tests. RESULTS: Autoradiographic analyses of [(3)H]raclopride binding to D2 sites revealed significant increases in the anterior caudate-putamen of mice in the EtOH-sensitized group when compared with either saline controls (+40%, P<0.00009) or to mice in the EtOH non-sensitized group (+32%; P<0.0003). Smaller increases were seen in the ventrolateral caudate-putamen of sensitized animals (+18% vs. control, P<0.02; and 12% vs. non-sensitized mice, P<0.07). No differences were found in other brain regions, including the nucleus accumbens, olfactory bulb and substantia nigra. CONCLUSIONS: The observed increases in D2-receptor binding in circumscribed targets of nigrostriatal projections may reflect either a pre-existing condition in sensitization-prone animals or a selective vulnerability of D2 receptors to chronic EtOH in these animals. In either case, it may be a marker for differential susceptibility to EtOH sensitization.

Antiulcerogenic effects of two Maytenus species in laboratory animals.

Leaves of Maytenus species are commonly used in Brazil for the treatment of gastric ulcers, dyspepsias and other gastric problems. The present study evaluated the antiulcerogenic potential of a boiling water extract of equal parts of M. aquifolium and M. ilicifolia leaves against ulcer lesions induced by indomethacin and cold-restraint stress in rats. Ranitidine and cimetidine were used as reference drugs. The oral and intraperitoneal administration of the extract had a potent antiulcerogenic effect against both types of ulcers. The extract was shown to cause an increase in volume and pH of gastric juice of the animals with the pH effects comparable to those of cimetidine. The results tend to confirm the popular use of the plant.

Increased stimulatory effect by the combined administration of cocaine and alcohol in mice.

Locomotor activity was recorded after 5-30 mg/kg of cocaine in mice pretreated or not with a stimulant dose of ethanol (2.0 g/kg). The increase in locomotion induced by the association of cocaine plus ethanol was significantly larger when compared to either the group injected with only cocaine or only ethanol.

Pharmacology of lemongrass (Cymbopogon citratus Stapf). II. Effects of daily two month administration in male and female rats and in offspring exposed "in utero".

An infusion (abafado) prepared from leaves of lemongrass (Cymbopogon citratus Stapf) administered orally to adult rats for 2 months, in doses up to 20 times larger than the estimated corresponding human dosage, did not induce any effect which could be taken as evidence of toxicity. An absence of effects was also noted in male and female rats and in their offspring when the abafado was administered prior to mating or during pregnancy. These data strongly suggest that lemongrass, as used in Brazilian folk medicine, has no toxic properties.