Birth insult alters ethanol preference in the adult rat

While genetic factors clearly play a role in regulating ethanol intake, the present study considered the possibility that early environmental factors which influence central nervous system development and long-term function might also alter ethanol intake. The specific aim of the study was to test whether alterations in birth condition, namely Caesarean section (C-section) birth and C-section birth with an added period of global anoxia, can affect subsequent ethanol preference in the adult rat. At 5 months of age, groups of experimental and vaginally born control rats were offered free choice between drinking water or various concentrations of ethanol (1-10% v/v) in water across 36 days of testing. Rats that had been born by C-section with 10 or 15 min of added global anoxia showed significant reductions in ethanol preference scores, in comparison to vaginally born controls. For the 10-min anoxia group, ethanol intake was decreased, water intake was increased and total fluid intake remained unchanged relative to values for vaginally born controls, across the entire test period. Although total fluid intake by the 15-min anoxia group also did not differ from that of vaginally born controls, the decreased ethanol preference scores in the 15-min anoxia group were mainly due to increased water intake during some test periods and a combination of reduced ethanol intake and increased water intake during others. Animals born by rapid C-section alone, with no added period of global anoxia, showed reduced ethanol preference only during a few early periods of testing, a much less pronounced effect than that observed for animals with added global anoxia. When animals were given the choice between drinking water vs. solutions of sucrose or NaCl, no group differences due to birth condition were found on measures of sucrose or NaCl preference. Together with reduced ethanol preference, the 10-min anoxia group showed a transient depression of locomotor activity in response to a low dose (0.25 g/kg) of intraperitoneal ethanol, which had no effect on locomotion in vaginally born controls. These results indicate that a relatively subtle alteration in birth condition, compatible with grossly normal development and behavior, is sufficient to alter ethanol preference in the adult rat.