Immediate and long-term behavioral effects of a single nicotine injection in adolescent and adult rats

We examined the acute rewarding as well as the long-term psychomotor altering effects of nicotine in early adolescent and adult male Sprague-Dawley rats. Place conditioning was used to examine nicotine-induced reward after a single drug pairing. A single pairing of nicotine with the initially non-preferred side of the place conditioning apparatus produced a conditioned place preference (CPP) in early adolescent but not adult animals. One month later, animals were given a nicotine challenge and locomotor activity observed in the open field to characterize age differences in the lasting alterations resulting from this single injection. Adult rats showed tolerance to the locomotor depressant effects of a low dose of nicotine whereas adolescent rats showed tolerance to a higher dose. Regardless of treatment group, animals tested during adolescence responded to the nicotine challenge with less hypoactivity when compared with animals tested as adults. The present results are in agreement with previous studies showing that early adolescent rats are more sensitive to nicotine's rewarding effects and are in accord with studies showing a unique profile of neurobehavioral alterations following nicotine exposure when compared with adults. Such findings are extended here by showing that these differences are seen following only a single pretreatment dose and persist for at least one month after pretreatment. (c) 2006 Elsevier Inc. All rights reserved.