Ontogeny of behavioral sensitization in the rat: effects of direct and indirect dopamine agonists.
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
In the present study, the abilities of NPA (a direct DA receptor agonist) and amphetamine (an indirect DA receptor agonist) to induce short- and long-term behavioral sensitization were assessed in 11- and 17-day-old rats (age at initial injection). Rats were injected on 4 consecutive days with amphetamine (1.0, 2.5, or 5.0 mg/kg), NPA (1.0 mg/kg), or saline. A final test day occurred either 2 days (experiment 1) or 8 days (experiment 2) later. On the test day, rats given successive agonist injections received a single injection of the same agonist again; whereas rats given successive saline injections received either amphetamine or NPA for the first time. Five minutes after injection, locomotor activity (line-crosses), stereotyped sniffing, and vertical activity were measured during a 30-min testing session. The results showed that 11- and 17-day-old rats exhibited behavioral sensitization when tested with NPA or amphetamine after a 2-day interval. In contrast, neither NPA nor amphetamine was able to sensitize the behaviors of preweanling rats when measured 8 days after initial drug treatments. Therefore, these results show that both direct and indirect DA agonists are able to induce short-term behavioral sensitization in preweanling rats, but that the mechanisms responsible for mediating long-term behavioral sensitization have not yet matured.
