Ethanol intake was explored in the Harrington derivation of the Maudsley Reactive and Maudsley Non-Reactive rat strains (MR/Har and MNRA/Har). When 5% and 10% ethanol solutions were presented as the sole source of fluid (1-bottle test), MR/Har rats, respectively, ingested 15% more, or 9% less, than their baseline water intake, whereas MNRAs ingested 6% less, or 42% less than their baseline intake. However, because MNRA/Har rats drank significantly more water than MR/Har's under ad libitum conditions (MNRA/Har, 46.6 +/- 1.83 ml; MR/Har 32.45 +/- 1.64 ml/24 hr), males and females of the two strains ingested a similar amount of ethanol in the 1-bottle test (5% ethanol, 4-7; 10% ethanol, 6-12 g/kg body weight/24 hr). In 2-bottle free-choice tests administered after an extended period of forced ethanol consumption, MR/Har male and female rats exhibited a strong ethanol preference (X = 80%) and consumed a larger amount of ethanol (MR/Har, 7-13; MNRA/Har, 6-9 g/kg body weight/24 hr) than MNRA/Har's. Across all conditions, females of both strains ingested a greater relative amount of ethanol than males. The strain difference in ethanol preference was found to be independent of prior exposure to ethanol because it was also found when 2-bottle free-choice tests were carried out in naive animals (Experiment 2). The pattern of development of ethanol preference in individual animals was characterized by abrupt onset, after variable periods of exposure to the 2-bottle choice test, and maintenance of strong ethanol preference thereafter. The extensive behavioral and biological definition of the Maudsley strains is a valuable asset in attempting to elucidate the biobehavioral correlates of ethanol preference.
"Therefore, they might not necessarily be co-selected when animals are selectively bred either for differences in emotionality or for differences in alcohol preference. For example, anxiety levels and alcohol drinking seem to correlate in sP (sardinian alcohol-preferring ) and in Indianapolis P (preferring) rats (Colombo et al. 1995; Stewart et al. 1993), but seem to be less consistently related in the Finnish alcohol-preferring AA (Alko Alcohol) rats (Tuominen et al. 1990; Fahlke et al. 1993; Möller et al. 1997b) and in MR (Maudsley reactive) rats (Brewster 1968, 1969; Adams et al. 1991; Overstreet et al. 1993). This interpretation is supported by a recent factor analysis of 18 behavioral measures from nine pairs of alcohol-preferring and nonpreferring rats (Overstreet et al. 1997). "
[Show abstract][Hide abstract] ABSTRACT: According to the tension reduction hypothesis, individuals with an elevated anxiety level may be more sensitive to the anxiolytic effects of alcohol and may, therefore, have a higher predisposition to consume alcohol. To examine this hypothesis, we studied the drinking behavior as well as the sensitivity to the anxiolytic effect of alcohol in two rat lines that were bred and selected for differences in anxiety-related behavior on the elevated plus-maze: the extremely anxious HAB (high anxiety-related behavior) and the non-anxious LAB (low anxiety-related behavior) lines. Alcohol self-administration and the occurrence of an alcohol deprivation effect were studied in female and male HAB and LAB rats in a free-choice, 4-bottle home cage paradigm. The sensitivity of HAB and LAB rats to the anxiolytic effect of alcohol was assessed by testing their behavior on the elevated plus-maze after an acute application of ethanol. During the first days of voluntary ethanol drinking, the ethanol intake and preference of female LABs was significantly higher than that of female HABs. Although not statistically significant, the same trend could be seen in male LABs. Moreover, male as well as female LAB but not HAB rats showed a significant alcohol deprivation effect after abstinence. There were no differences when saccharin was presented to naive animals, indicating that the different ethanol drinking behavior of HAB and LAB rats does not represent a general difference in the consumption of new liquids. Application of ethanol resulted in an anxiolytic effect in HAB but not in LAB rats on the elevated plus-maze. In summary, increased inborn anxiety and voluntary ethanol consumption of HAB and LAB rats were correlated to some extent; however, this relationship was a negative one. It is concluded that, although such a relationship might exist in some individuals, increased levels of inborn anxiety and alcohol consumption are not necessarily related.
"Together these findings suggest that female neonates are more sensitive than males to ethanol. Although gender differences in responsiveness to ethanol are common in adult rats (Adams et al., 1991; Lancaster and Spiegel, 1992; Li and Lumeng, 1984), they have not been observed previously in preweanling animals (Chotro et al., 1996; Lee et al., 1998; McKinzie et al., 1999; Molina et al., 1999). Given strong interaction between gender and ethanol concentration associated with ethanol intake (Varlinskaya et al., 1999), the effectiveness of orally processed ethanol as a US (experiments 5 and 6), and the absence of an effect of gender when ethanol had minimal orosensory consequences but was nevertheless an effective US and reinforcer (experiment 8), it is likely that neonatal male and female rats perceive orosensory properties of ethanol differently . "
[Show abstract][Hide abstract] ABSTRACT: Recent evidence suggests that human infants prefer alcohol-flavored milk when fed through a bottle. Animal models also indicate a surprising predisposition for neonatal and infant rats to voluntarily and willingly ingest ethanol. These findings suggest high susceptibility to the reinforcing properties of ethanol early in ontogeny.
A surrogate nipple technique-a highly effective tool for investigation of the reinforcing properties of different fluids-was applied in the present study. Tests of ethanol reinforcement were accomplished in terms of two basic paradigms of Pavlovian conditioning. In one paradigm, the conditioned stimulus (CS) was the surrogate nipple, and in the other, the CS was a novel odor.
Newborn rats showed sustained attachment to the nipple providing 5% ethanol, and later reproduced this behavioral pattern toward the empty nipple (CS alone). Ingestion of ethanol yielding appetitive reinforcement was accompanied by detectable blood alcohol concentrations, with most in the range of 20-30 mg/dl. The reinforcing efficacy of ethanol was also confirmed in the classical olfactory conditioning paradigm: following pairing with intraoral ethanol infusions, the odor (CS) alone elicited sustained attachment to an empty nipple. Females showed better olfactory conditioning with low concentrations of ethanol, whereas males were effectively more conditioned to high concentrations. Although there were no reinforcing consequences of intraperitoneally injected ethanol [as an unconditioned stimulus (US)] when a neutral odor was the CS, when paired with ingestion of water from a nipple, the injection of ethanol had a reinforcing effect.
The present series of experiments revealed ethanol reinforcement in the newborn rat. Two varieties of Pavlovian conditioning established that ethanol can serve as an effective US, and hence reinforcer, in such a way as to increase the approach and responsiveness toward stimuli paired with that US, indicating appetitive reinforcement.
Alcoholism Clinical and Experimental Research 04/2001; 25(3):391-402. DOI:10.1111/j.1530-0277.2001.tb02226.x · 3.21 Impact Factor
"These include the Chilean UChB (Mardones and Segovia-Requelme, 1983), Finnish AA (Kiianmaa et al, 1991), Indiana P (Li et al., 1987), and Sardinian sP (Colombo, 1997) rat lines, in comparison with their corresponding -non-preferring control counterparts (UChA, ANA, NP, and sNP respectively). Two other rat strains have also been identified as alcohol-preferring, namely the Fawn-Hooded (Rezvani et al., 1990; Overstreet et al, 1993) and the Maudsley Reactive (Satinder, 1972; Adams et al., 1991) rats, in comparison with ordinary Wistar (Sprague-Dawley) and the 'Present address: Department of Biochemistry, University of Karachi, Karachi 75270, Pakistan. "Author to whom correspondence should be addressed. "
[Show abstract][Hide abstract] ABSTRACT: Parameters of tryptophan (Trp) and related metabolism were compared in male Sardinian alcohol-preferring (sP) and -non-preferring (sNP) rats. Liver Trp pyrrolase activity was 38-58% higher in sP than in sNP rats, and this was associated with a greater expression of the enzyme mRNA as measured by multiprobe oligonucleotide solution hybridization. Moderately (about 10-19%), but significantly, lower concentrations of free serum, total serum, and brain Trp were also observed in sP compared with sNP rats. Concentrations of whole brain 5-hydroxytryptamine (5-HT) and its major metabolite 5-hydroxyindol-3-yl-acetic acid (5-HIAA) were, however, 14-21% higher in sP rats. Serum corticosterone concentration was 18% higher in sP rats. We conclude that alcohol preference in Sardinian rats is associated with increased liver Trp pyrrolase activity and mRNA expression leading to a decrease in Trp availability to the brain. Although a simple serotonin deficiency could not be demonstrated in the whole brain, the possibility could not be ruled out that a deficiency may be present in discrete areas of the brain of the sP rat.
Alcohol and Alcoholism 05/1998; 33(3):220-5. DOI:10.1093/oxfordjournals.alcalc.a008385 · 2.89 Impact Factor
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