Environmental influences on the failure to drink in inbred rats with an ethanol preference

To investigate the environmental influences on the initiation of voluntary consumption of 10% ethanol (EtOH) in rats with differing genetic susceptibi lity to excessive EtOH consumption, Maudsley reactive (MR/Har) and nonreact ive (MNRA/Har) inbred rats were observed in different types of caging envir onments. Singly housed male and female rats of both strains living in Obser vational (O) cages drank markedly less EtOH during 3 weeks of two-bottle ch oice than did rats living in standard-control (C) individual cages. When ma le rats had a preexisting moderate or heavy pattern of EtOH intake (manipul ated through prior EtOH experience), moving to the O cage did not reduce Et OH intake. To investigate the: nature of the above cage effect (the reduced initiation of EtOH consumption), we compared the manner in which food had been distributed (traditional food hopper in C cages versus loose distribut ion in O cages) independently of cage type. The results showed that MR/Har male rats that obtained food through a hopper in both O or C cages drank si gnificantly more EtOH than rats that had food loosely distributed in the O or C cages. The results suggest that differences in the mode of food procur ement and caging can play a large role in whether the phenotype for excessi ve EtOH intake is expressed in the acquisition of an EtOH preference in gen etically vulnerable rats. (C) 2000 Elsevier Science Inc. All rights reserve d.