Ethanol acceptance is high during early infancy and becomes still higher after previous ethanol ingestion

Infant (preweanling) rats readily accept ethanol without initiation procedures. During their second and third postnatal weeks, rats ingest large quantities of even high concentrations of ethanol. The present study tested the consequences of still earlier exposure to ethanol differing in concentration, mode of administration, and contextual circumstances.

Every 48 hours from postnatal day 2 (P2) to P10, pups were given access to 0, 5, 15, or 25% ethanol through an independent feeding procedure (consumption off the floor; COF) or by intragastric (i.g.) administration. The amount of ethanol consumed was matched for the 2 modes of ethanol delivery. On P12 pups were tested for intake of 15% ethanol through an intraoral infusion test or COF.

Beginning on P6, pups ingested more ethanol solution than water, and by P8 and P10 they ingested large quantities of ethanol--1.5 to 2.0 g/kg ethanol from 15 or 25% ethanol solution within a 10-minute period. This early experience with ingestion of ethanol increased subsequent ethanol intake on P12, particularly when concentration and mode of ingestion were the same as before.

Intake on P12 was increased by prior exposure to ethanol intragastrically as well as by the conventional oral route, suggesting pharmacological effects of prior ethanol exposure. Yet, the apparently greater influence of prior exposure by the oral route and the influence of prior ethanol concentration also implicate the importance of ethanol's chemosensory attributes for effects of prior ethanol exposure. The equivalent g/kg intake of ethanol in 15 or 25% solutions during the early part of the second postnatal week suggests that regulation of ethanol intake at P8 and P10 is similar to that observed previously in adults. Change in aspects of ethanol ingestion at about P6 may reflect the shift in function of the GABA system at about this age.