Farrar A M, Font L, Pereira M, Mingote S, Bunce J G, Chrobak J J, Salamone J D
Department of Psychology, University of Connecticut, Storrs, CT 06269-1020, USA.
Neuroscience. 2008 Mar 18;152(2):321-30. doi: 10.1016/j.neuroscience.2007.12.034. Epub 2008 Jan 1.
Organisms often make effort-related choices based upon assessments of motivational value and work requirements. Nucleus accumbens dopamine is a critical component of the brain circuitry regulating work output in reinforcement-seeking behavior. Rats with accumbens dopamine depletions reallocate their instrumental behavior away from food-reinforced tasks that have high response requirements, and instead they select a less-effortful type of food-seeking behavior. The ventral pallidum is a brain area that receives substantial GABAergic input from nucleus accumbens. It was hypothesized that stimulation of GABA(A) receptors in the ventral pallidum would result in behavioral effects that resemble those produced by interference with accumbens dopamine transmission. The present studies employed a concurrent choice lever pressing/chow intake procedure; with this task, interference with accumbens dopamine transmission shifts choice behavior such that lever pressing for food is decreased but chow intake is increased. In the present experiments, infusions of the GABA(A) agonist muscimol (5.0-10.0 ng) into the ventral pallidum decreased lever pressing for preferred food, but increased consumption of the less preferred chow. In contrast, ventral pallidal infusions of muscimol (10.0 ng) had no significant effect on preference for the palatable food in free-feeding choice tests. Furthermore, injections of muscimol into a control site dorsal to the ventral pallidum produced no significant effects on lever pressing and chow intake. These data indicate that stimulation of GABA receptors in ventral pallidum produces behavioral effects similar to those produced by accumbens dopamine depletions. Ventral pallidum appears to be a component of the brain circuitry regulating response allocation and effort-related choice behavior, and may act to convey information from nucleus accumbens to other parts of this circuitry. This research may have implications for understanding the brain mechanisms involved in energy-related psychiatric dysfunctions such as psychomotor retardation in depression, anergia, and apathy.
生物体常常根据对动机价值和工作要求的评估来做出与努力相关的选择。伏隔核多巴胺是调节强化寻求行为中工作输出的大脑回路的关键组成部分。伏隔核多巴胺耗竭的大鼠会将其工具性行为从具有高反应要求的食物强化任务中重新分配，转而选择一种不那么费力的觅食行为类型。腹侧苍白球是一个从伏隔核接收大量GABA能输入的脑区。据推测，刺激腹侧苍白球中的GABA(A)受体将产生类似于干扰伏隔核多巴胺传递所产生的行为效应。本研究采用了同时选择杠杆按压/食物摄取程序；在这个任务中，干扰伏隔核多巴胺传递会改变选择行为，使得为获取食物而进行的杠杆按压减少，但食物摄取增加。在本实验中，向腹侧苍白球注入GABA(A)激动剂蝇蕈醇（5.0 - 10.0纳克）会减少对偏好食物的杠杆按压，但会增加对不太偏好食物的摄取。相比之下，在自由进食选择测试中，向腹侧苍白球注入蝇蕈醇（10.0纳克）对美味食物的偏好没有显著影响。此外，向腹侧苍白球背侧的一个对照部位注射蝇蕈醇对杠杆按压和食物摄取没有显著影响。这些数据表明，刺激腹侧苍白球中的GABA受体产生的行为效应类似于伏隔核多巴胺耗竭所产生的效应。腹侧苍白球似乎是调节反应分配和与努力相关的选择行为的大脑回路的一个组成部分，并且可能起到将信息从伏隔核传递到该回路其他部分的作用。这项研究可能对理解与能量相关的精神功能障碍（如抑郁症中的精神运动迟缓、无力和冷漠）所涉及的脑机制具有启示意义。
