CHRONIC CONDITIONED TOLERANCE TO ETHANOL-INDUCED LOCOMOTOR STIMULATION IN THE INFANT RAT

CASTELLO, S; REVILLO, D.A.; ARIAS, C; MOLINA, J.C.

Santiago

Congreso; Latin American Research Network in Drug Addiction; 2012

Latin American Research Network in Drug Addiction

Relatively high ethanol doses (between 1.25 and 2.5 g/kg) induce acute locomotor stimulating effects in preweanling rats, an effect associated with its rewarding properties. The locomotor stimulating effect of ethanol is rapidly attenuated after repeated ethanol administration (tolerance) in preweanling or adult rats. Baseline locomotor activity predicts the magnitude of this ethanol effect at both ages. The goals of the present work were to analyze whether tolerance-induced by ethanol is context-dependent (conditioned tolerance) in Wistar infant rats, and to explore whether a behavioral phenotype based on the initial exploration of an environment during the first postnatal week of life can predict a response to ethanol one week later. Baseline locomotor activity was registered on postnatal day 8 (PD 8). Then, subjects (PDs 8-12) received 0 or 2.5 g/kg ethanol before being placed in an open field containing an odor cue. On PD 15 pups were tested in an open field after being injected with ethanol (0 or 2.5 g/kg) in presence or absence of the odor. Results showed ethanol induced locomotor activating effects in infant rats (PDs 8 to PD15). Repeated exposure to the drug did not induce tolerance when pups were tested in absence of the odor cue, but when the odor was present there were conditioned tolerance to the stimulating effect. Besides, baseline activity (on PD 8) predicted ethanol response on PD 15, independently of the presence of the odor cue. These results suggest the possibility to use early behavioral markers to predict unconditioned effects of ethanol.