Neonatal operant responding controlled by the reinforcing effects of milk and ethanol.

ARIAS, C; MOLINA, A; SPEAR, N.E.; MOLINA, J.C.

Granada - Espana

Congreso; XVIIth Congress of the European Chemoreception Research Organisation (ECRO); 2006

European Chemoreception Research Organisation (ECRO)

Newborn rats are able to obtain milk when suckling from a surrogate nipple. While attached to this nipple, they also display vigorous head and forepaws movements similar to those exhibited during breastfeeding. In this study the probability of execution of these movements was analyzed as a function of the contingency existing between these behaviors and intraoral infusions of a natural reinforcer (milk), a relatively neutral stimulus (water) or ethanol (3% v/v). The main goal was to analyze whether ethanol?s sensory cues act as a positive reinforcer leading towards self-administration of this psychopharmacological agent. These goals were examined using a new technique in which 5-day-old rat pups were positioned over a soft texture while having access to a touch sensitive sensor. Forepaw or head movements leading to the activation of the sensor resulted in intraoral infusions of the above described fluids (Paired groups). Yoked controls were employed for each of these solutions. All pups were subjected to two training trials (15 min each) followed by a 9-min extinction trial. Paired pups were found to rapidly increase their rate of responsiveness when reinforced with milk. During extinction these pups still exhibited higher levels of responding when compared with appropriate controls. When ethanol served as the reinforcer clear differences, similar to those observed in milk reinforced pups, emerged during extinction. Water was not found to modify performance patterns of Paired pups when compared with Yoked infants during training or extincition. These results indicate that newborns rapidly acquire operant responses when reinforced with milk. Furthermore, these results indicate that ethanol is highly reinforcing during early postnatal development.