THE BEHAVIOR OF RATS SELECTED FOR THEIR VOLUNTARY ETHANOL-CONSUMPTION

  • 1 January 1987
    • journal article
    • research article
    • Vol. 38  (3-4) , 409-424
Abstract
New strains of rats, preferent (HAP) and non-preferent (NAP) for ethanol were selectively outbred from a Wistar stock. The strains have now been raised to the F13 generation. The F9/10 animals, selected for this behaivioural investigation, exhibited a significant phenotypic drinking behaviour and/or ethanol consumption. During a free choice between tap water and 10% ethanol solution (v/v), the mean daily alcohol intake for male and female HAP rats was 8.42 .+-. 0.67 g/kg/24 h (n = 20 o) and 11.50 .+-. 0.42 g/kg/24 h (n =20 o) for male and female NAP rats 0.74 .+-. 0.09 g/kg/24 h (n = 20 0) and 1.76.+-. 0.20 g/kg/24 h (n = 20 o), respectively. The NAP rats exhibited a strong aversion to the 10% ethanol solution when it was the only source fluid. In the open-field test (OFT), as compared to the NAP rats, male individuals of the HAP strain showed a lower motility in the first minute, in penetration into the inner squares, showed a longer latency to start exploration (latency to leave the center), exhibited larger rearing and grooming activity and shorter latencies to start these activities. The defecation rate was smaller and latency to defecation prolonged. Female HAP rats showed higher activity scores in penetration of outer and inner squares and a shorter latency to start exploration. They also had higher rearing but smaller grooming activity. The females exhibited identical defecation but different urination behavior in comparison to the males. The time-to-emerge latencies of HAP rats were longer than in NAP individuals. In the plus-maze test (PMT), male and female HAP rats spent less time in the open arms, showed a smaller number of open-arm entries and they choose significantly fewer open arms as the first entry. The defectation rate of HAP rats was greater than of the NAP individuals. The data suggest that HAP rats possibly had difficulties in becoming accustomed to a new and stressful environment and are more emotional (anxious) than the NAP counterparts. This inability seems to be one of the internal factors which might underlie their preference for the anticonflict properties of ethanol. Thus, the role of predisposing factors might be one of the dominanting components in voluntary ethanol preference and functions as a learned adaptive response to attenuate the effect of stress.