Free choice ethanol intake of laboratory rats under different social conditions

Abstract

To study the effects of different kinds of social deprivation on voluntary ethanol (ETOH) intake male Wistar rats were housed by (a) individual caging, (b) "contact" caging (partial social deprivation), and (c) group caging (four individuals per cage). In the latter condition the individuals were separated once a week from each other for 24 h. The rats simultaneously received water 5%, 10% and 20% ETOH for a period of 14 weeks. Additional control animals received water. Isolated individuals drank significantly more alcohol than group-housed or contact-caged rats. After a few days they preferred the 20% solution. Circadian measures revealed a discontinuous intake of high doses (greater than 0.5 g/kg/h) during short time periods. Contact-caged rats consumed much less ETOH, but both the preference for 20% ETOH and the circadian course of intake were similar to those occurring after isolation. ETOH intake of group-housed individuals was low. These individuals preferred the 5% solution and continuously consumed small ETOH doses. During the period of short-term isolation they drank even more ETOH than long-term isolated individuals. In contrast to the latter, the enhancement of intake decreased after some weeks. It is suggested that the differences between the housing groups not only reflect different degrees of isolation stress, but may also be explained by a contribution of different reinforcing or aversive psychotropic effects of ETOH. Reduction of isolation stress is probably most important in the situation of short term separation, whereas dose-dependent reinforcement via social stimulation or sedation may affect the drug taking behavior under the other social conditions.

Sex-Dependent Modulation of Ethanol Consumption in Vesicular Monoamine Transporter 2 (VMAT2) and Dopamine Transporter (DAT) Knockout Mice

“…The effects of genotype were only observed at high ethanol concentrations. Such concentration dependencies have been noted previously in the effects of isolation rearing (Wolffgramm, 1990;Hall et al, 1998) and strain (Hall et al, 1998) on ethanol consumption in rats. The reasons for concentration dependencies are unknown; however it might be speculated that if ethanol produces rewarding effects through multiple mechanisms, then this might be differentially activated by different doses of ethanol.…”

Social and environmental enrichment has different effects on ethanol and sucrose consumption in mice

“…Pang and colleagues demonstrated that the provision of social or environmental enrichment reduces ethanol consumption in female C57BL/6 mice (Pang et al, 2013). Wolffgramm and colleagues produced a similar result in male Wistar rats (Wolffgramm, 1990). They allowed sensory contact (sight, smell, vocal communication) without physical contact by placing a perforated divider in the cage and housing a rat on either side of the divider.…”

“…To date, the majority of preclinical research investigating the impact of social and environmental enrichment on ethanol and sucrose consumption has been directed toward ethanol consumption (see Tables 1 and 2). While there is considerable methodological variation between the models used in these studies (species, strain, ethanol concentration, type and length of ethanol access), they generally show that social deprivation (individual rather than group housing) increases ethanol consumption (Lodge & Lawrence, 2003;Schenk, Gorman, & Amit, 1990;Wolffgramm, 1990;Wolffgramm & Heyne, 1991). The role of other types of environmental enrichment designed to provide physical and/or cognitive stimulation is less clear.…”

“…It remains, however, undetermined whether moving rats from deprived environments to enriched environments and vice versa impacts subsequent sucrose consumption, similar to ethanol consumption. If indeed social and environmental factors are not important for specific aspects of sucrose consumption behavior, this feature would make sucrose consumption unique to other substances of abuse, like morphine, cocaine, nicotine, and ethanol (Wolffgramm, 1990;Alexander, Beyerstein, Hadaway, & Coambs, 1981;Gipson, Beckmann, El-Maraghi, Marusich, & Bardo, 2011;Mesa-Gresa, Ramos-Campos, & Redolat, 2013), and could be utilized to, not only, improve our understanding and treatment of AUDs (and other addictions), but also to enhance our understanding of the factors which drive excessive sucrose consumption and our ability to prevent and treat obesity.…”

The Effects of Proximal and Distal Social Stimulation on Ethanol Intake in Male and Female CD-1 Mice

“…The stimulating effects of direct proximal social interactions on ethanol intake have also been reported in a number of rodent species, including rats [6,7,8,9,10,11,12,13], mice [14,15,16], and prairie voles [17,18]. It should be noted that several early investigations employing animal subjects evaluated the effects of social stimulation by comparing ethanol consumption in isolation-housed versus group-housed rodents, and found little evidence of social stimulation of ethanol drinking [7,8,16,19,20].…”