McDougall S A, Duke M A, Bolanos C A, Crawford C A
Department of Psychology, California State University, San Bernardino 92407.
Psychopharmacology (Berl). 1994 Dec;116(4):483-90. doi: 10.1007/BF02247482.
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.
在本研究中，评估了NPA（一种直接的多巴胺受体激动剂）和苯丙胺（一种间接的多巴胺受体激动剂）在11日龄和17日龄大鼠（初次注射时的年龄）中诱导短期和长期行为敏化的能力。大鼠连续4天注射苯丙胺（1.0、2.5或5.0mg/kg）、NPA（1.0mg/kg）或生理盐水。最终测试日在2天后（实验1）或8天后（实验2）进行。在测试日，连续接受激动剂注射的大鼠再次接受一次相同激动剂的注射；而连续接受生理盐水注射的大鼠首次接受苯丙胺或NPA注射。注射后5分钟，在30分钟的测试期间测量运动活性（穿越次数）、刻板嗅探和垂直活动。结果表明，11日龄和17日龄大鼠在间隔2天后用NPA或苯丙胺测试时表现出行为敏化。相比之下，在初次药物治疗8天后测量时，NPA和苯丙胺均不能使断奶前大鼠的行为产生敏化。因此，这些结果表明，直接和间接的多巴胺激动剂都能够在断奶前大鼠中诱导短期行为敏化，但介导长期行为敏化的机制尚未成熟。
