CONICET | Buscador de Institutos y Recursos Humanos

Aversive as well as appetitive attributes of ethanol (EtoH) have been observed in young organisms utilizing classical conditioning techniques. Yet, the development of ethanol self-administration tasks are desirable in order to better understand the human pattern of consumption. Recently, it has been observed (Ponce et al, 2006) that a brief pre-exposure to intraoral ethanol (7.5% v/v) during postnatal day 13 (PD13) seems to facilitate later self-administration of EtOH in an operant conditioning task. The main goal of this work was to more sistematically assess the effects of ethanol pre-exposure upon later self-administration of the drug during infancy and periadolescence. Thirteen-days-old pups were passively intraorally infused with either ethanol (7.5% v/v) or water during PD 13 (Experiment I). Then, daily operant training sessions were conducted (PDs 14-17). Nose-poking was reinforced with either intraoral water or ethanol (3.75% v/v). A significantly increased amount of nose poking for EtOH was observed, relative to pertinent controls, in those animals that had been pre-exposed to EtOH. Regardless preexposure treatment, blood ethanol concentrations on PD 17 ranged between 31-49 mg%. Experiment II employed animals derived from a similar operant training procedure as the one described for Experiment 1. Rats had been pre-exposed to 7.5% v/v ethanol and trained with water, 3.75% or 7.5% v/v EtOH during PDs 14-17. During periadolescence (PDs 30-33), they were evaluated in a free-choice ethanol intake test. Animals had free access to water and a given ethanol solution two hours a day (3% v/v for the first day; 1% v/v of increment each day). Rats trained with ethanol in the infantile operant task with a history of pre-exposure to the drug exhibited higher levels of ethanol intake when compared with their respective controls. Taken together, these results indicate that EtOH pre-exposure during infancy allows the expression of ethanols appetitive reinforcing properties in the young rat; an effect that persists at least until the periadolescent stage. Familiarization with ethanol orosensory properties, development of tolerance to the drugs aversive properties and/or sensititizacion to its positive reinforcing effects could be underlying the effects under discussion.

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