Patterns of ethanol and saccharin intake in P rats under limited-access conditions

Patterns of drinking and responding for ethanol (EtOH) and saccharin (SACC) were examined in the alcohol-preferring P rat using Various limited-access paradigms. Adult female P rats (n = 10-20) were given 2-h access to EtOH ( 10-13% v/v) and SACC (0.0125% g/v) concurrently each day, or each solution individually on alternate days. Total 2-h SACC intake was significantly gre ater than EtOH under both concurrent (12 +/- 2 vs. 7 +/- 0 0.8 ml, p < 0.05 ) and alternate-day access (18 +/- 1.6 vs. 10 +/- 0.5 ml) conditions. Under both conditions, however, EtOH intake (over 55% of the total) in the first 15 min was significantly greater than that of SACC (< 25% of total). In an operant paradigm, total responding for EtOH (124 +/- 29) and SACC (114 +/- 7) under 2-h alternate-day conditions did not differ, but 65% of total EtO H responding occurred during the first 20 min versus less than 45% for SACC (p < 0.05). Increasing response requirements (FR-1 to FR-5) did not signif icantly alter the total number of EtOH reinforcements, but decreased the to tal number of SACC reinforcements by approximately 50% (p < 0.05). Increasi ng the EtOH concentration from 15% to 35% decreased the number of reinforce ments approximately 50% but did not decrease the estimated g/kg EtOH intake . Increasing the SACC concentration from 0.0125% to 0.05%, however, nearly doubled the number of reinforcements. The greater preference for EtOH versu s SACC during the initial part of the access period, together with the main tenance of EtOH intake in g/kg when the response requirements and the EtOH concentration were increased, suggests that EtOH intake is motivated by pha rmacological consequences. Therefore, different motivational factors appear to underlie EtOH and SACC intake of the P rat. Furthermore, the pattern of EtOH intake and responding displayed by the P rat may be the result of a " bout-" or "binge-" like loss of control under restricted EtOH access condit ions. (C) 1999 Elsevier Science Inc. All rights reserved.