Ontogeny of amphetamine- and LiCl- induced taste avoidance in the infant rat.

REVILLO, D.A.; SPAER, N.E.; MOLINA, J.C.; ARIAS, C

Congreso; XXV Reunión Anual de la Sociedad Argentina de Neurociencias; 2010

Background: Drug of abuse produces taste avoidance in rats. Parker (2003) interpreted this avoidance as a kind of fear conditioning. In other hand, Sullivan and cols. (2000) described a sensitive period in the infant rat [until postnatal day (PD) 10 approximately], where some aversive stimuli can produce conditioned preferences instead of conditioned fear. During this ontogenetic period, corticosterone plays a pivotal role in this learning. Goals: To evaluate taste avoidance induced by amphetamine in the infant rat within (PD7) and after (PD14) the sensitive period (experiment 1), and compare the capability to acquire this specific learning with conditioned taste aversion induced by lithium chloride (LiCl) (Experiment 2). In Experiment 4 we evaluated the role of corticosterone hormone in conditioned taste avoidance before and after PD10. Hypotheses: The working hypotheses guiding the present study are as follows: a) Infants will express taste aversion (by LiCl) and taste avoidance (by amphetamine) after the sensitive period ( after PD10). Before PD10 infants will acquire taste aversion induced by LiCl; In contrast amphetamine will generate conditioned taste preference. C) Before PD10 amphetamine will induce conditioned avoidance when subjects are given corticosterone before training. And after PD10 metyrapone will reduce conditioned taste avoidance mediated by amphetamine. Results: After PD10, both amphetamine and LiCl produce taste avoidance, while before PD10 this effect was observed with LiCl. Corticosterone did not affect the effects induced by amphetamine before or after PD10. Conclusion: These results supports the existence of differences between the ontogenetic development of taste avoidance induced by amphetamine and taste aversion induced by LiCl, and also, the hypothesis postulating different mechanisms underlying both learning processes. The present ontogenetic model may represent a valuable tool to explore neuronal mechanisms regulation taste avoidance induced by drugs of abuse or emetic treatment.