Hull E M, Bazzett T J, Warner R K, Eaton R C, Thompson J T
Department of Psychology, State University of New York at Buffalo, Amherst 14260.
Brain Res. 1990 Mar 26;512(1):1-6. doi: 10.1016/0006-8993(90)91162-a.
The mesocorticolimbic dopamine tract is considered to be a substrate for motivation and reward as well as for locomotor behavior. The present experiments assessed the role of dopamine cell bodies in the ventral tegmental area (VTA), the source of this tract, in the copulatory behavior of male rats. The dopamine agonist apomorphine or the dopamine antagonist cis-flupenthixol were microinjected into the VTA immediately before sexual behavior tests with a receptive female. Apomorphine delayed the onset of copulation and slowed its rate, presumably by stimulating somatodendritic autoreceptors and thereby decreasing the firing rate of VTA neurons. Control injections of apomorphine into the substantia nigra were without effect. cis-Flupenthixol, which would have blocked autoreceptors and thereby depolarized VTA neurons, shortened the latency to begin copulating in those animals that did copulate; however, fewer animals exhibited sexual behavior. One possible explanation for the apparently contradictory effects of cis-flupenthixol may be that VTA neurons increased their rate of firing in some animals, leading to a faster onset of copulation, but that in other animals depolarization block in a substantial number of neurons resulted in a lack of copulation. These results are consistent with a contribution of the mesocorticolimbic dopamine tract to motivational and/or motor aspects of male copulatory behavior.
中脑皮质边缘多巴胺通路被认为是动机、奖赏以及运动行为的基础。本实验评估了多巴胺细胞体在腹侧被盖区（VTA），即该通路的起源部位，在雄性大鼠交配行为中的作用。在与处于接受状态的雌性大鼠进行性行为测试前，将多巴胺激动剂阿扑吗啡或多巴胺拮抗剂顺式氟奋乃静微量注射到VTA中。阿扑吗啡延迟了交配的开始并减缓了其速度，推测是通过刺激树突体自身受体从而降低VTA神经元的放电频率。向黑质中注射对照剂量的阿扑吗啡则没有效果。顺式氟奋乃静本应阻断自身受体从而使VTA神经元去极化，它缩短了那些确实进行交配的动物开始交配的潜伏期；然而，进行性行为的动物数量减少了。对于顺式氟奋乃静明显矛盾的作用，一种可能的解释是，VTA神经元在一些动物中提高了其放电频率，导致交配开始得更快，但在其他动物中，大量神经元的去极化阻滞导致了交配行为的缺失。这些结果与中脑皮质边缘多巴胺通路对雄性交配行为的动机和/或运动方面的作用是一致的。
