Tyrka A, Gayle C, Smith G P
Department of Psychiatry, Cornell University Medical College, New York, NY 10021.
Pharmacol Biochem Behav. 1992 Nov;43(3):863-9. doi: 10.1016/0091-3057(92)90419-g.
To investigate the role of dopaminergic activity at D2 receptors in the mediation of the positive reinforcing effect of sucrose on ingestion in preweanling rats, we tested the effects of the D2 antagonist, raclopride, on the intake of 10% sucrose of rats on postnatal days (PN) 7, 14, and 21. Intake was measured during independent ingestion tests in which pups licked sucrose from the floor of a beaker and during oral catheter tests in which sucrose was continuously infused through an anterior, sublingual, oral catheter. Rats were tested once to eliminate the possibility that repeated test experience would affect the response to raclopride. Pretreatment with raclopride resulted in decreased intake in independent ingestion (II) tests, but not in oral catheter (OC) tests on PN 7, 14, and 21. The inhibition of intake was not due to a generalized motor deficit because raclopride did not affect latency to eat, time-sampled activity scores, or latency to withdraw the hindlimb from a raised position. These results demonstrate that dopaminergic activity at D2 receptors is necessary for the positive reinforcing effect of sucrose that maintains ingestion in the II test but not in the OC test.
为了研究多巴胺能活性在D2受体介导的蔗糖对断奶前大鼠摄食的正性强化作用中的作用，我们测试了D2拮抗剂雷氯必利对出生后第7、14和21天大鼠摄入10%蔗糖的影响。在独立摄食测试中测量摄入量，幼崽从烧杯底部舔食蔗糖；在口腔导管测试中，通过一根位于舌下前方的口腔导管持续输注蔗糖。对大鼠进行一次测试，以排除重复测试经历会影响对雷氯必利反应的可能性。在出生后第7、14和21天，雷氯必利预处理导致独立摄食（II）测试中的摄入量减少，但在口腔导管（OC）测试中未减少。摄入量的抑制并非由于全身性运动缺陷，因为雷氯必利不影响进食潜伏期、时间抽样活动评分或后肢从抬起位置撤回的潜伏期。这些结果表明，D2受体处的多巴胺能活性对于维持II测试中摄食的蔗糖正性强化作用是必要的，但在OC测试中则不然。
