Development of rapid tolerance in preweanling rats expressed through changes in motor elicited patterns.

PUETA, M.; SPEAR, N.E.; MOLINA, J.C.

Santa Barbara, California.

Congreso; 28th Scientific Meeting of the Research Society on Alcoholism; 2005

Research Society on Alcoholism

DEVELOPMENT OF RAPID TOLERANCE IN PREWEANLING RATS EXPRESSED THROUGH CHANGES IN MOTOR ELICITED PATTERNS. M. Pueta, N.E. Spear & J.C. Molina. Instituto de Investigación Médica  M.M. Ferreyra, Argentina and Dept. of Psychology, Binghamton University.   Rapid tolerance has been defined as the diminished response to alcohol upon administration of a second dose within 24 hr after the first experience with the drug. To our knowledge, this phenomenon has not been still reported in preweanling animals. Previous literature has argued that neurobiological mechanisms underlying the development of this type of tolerance are still immature during infancy. In this study we report experimental evidence suggesting the expression of rapid tolerance to disruptive motor effects of ethanol in preweanling rats that were stimulated with salient gustatory cues. At postnatal days (PDs) 15, 16 and 17, infants were subjected to intraoral stimulation provided with water, a 0.004% w/v quinine solution or a 5% w/v sucrose solution during 20 m. At PDs 15 and 16, pups received an i.g administration of water or ethanol (0.5 or 1.0 g/kg). At PD 17 all pups received an i.g. administration of water. Intake scores of the different fluids were calculated and behavioral responsiveness (locomotion, wall climbing and facial wiping) to each of them was also recorded. At PD 18 all pups received an i.g. administration of 1g/kg ethanol and blood alcohol levels were determined at postadministration time 30 min. As could be expected sucrose was always consumed more than water or the quinine solution. Within each day of assessment, ethanol treatment failed to affect consumption patterns of each particular solution. The most important result derived from this study focuses on preweanling locomotion behavior. During PD 15, pups administered with the highest ethanol dose (1 g/kg) showed significant decreases in locomotion elicited by the three fluids. However, during PD 16 this sedative effect of the 1 g/kg ethanol dose was no longer observed. Prior ethanol treatment did not affected the pattern of elicited behaviors when pups were later tested under sobriety (PD17). In terms of blood alcohol levels, no differences across previous ethanol treatments were observed. The present results suggest the development of rapid behavioral tolerance in preweanling rats. The pattern of motor elicited behaviors is not explainable through the development of metabolic tolerance or through deleterious effects of the drug upon the capability to sense and or respond to particular sensory characteristics of the fluids here utilized.