引用

哺乳动物的行为很大程度上取决于个体及其对刺激的反应。从原则上讲，它基于两种系统，一种是根深蒂固的反射机制，另一种是自由选择的行动，它们通常在最广泛的意义上调节体内平衡的必要性。这些行为本身在情感上是中立的。为了让一个人做出这种心理上无关紧要的行为，大自然发展了一种特殊的大脑回路，即奖励系统。它主要由多巴胺能和血清素能的中脑核和它们的主要投射目标，伏隔核和内侧眶额皮层组成。不是生理上的需要，而是在进食或性交等自我平衡活动后的宏大的内在感觉，使个人反复进行这些行为。为了达到反管制的目的，必须有一个相反的系统，它破坏了在不令人满意的情况下的享乐情绪。脊椎动物大脑中的这种反奖励系统由缰核及其内侧(MHb)，尤其是外侧(LHb)复合物表示。这个处理大量输入的中心评估给定的情况，并适当地减少腹侧被盖区(VTA)的多巴胺能活动，从而导致享乐感的缺失。为了完成反奖励信号循环，必须有某种类型的反馈从VTA到LHb。 In the present investigation the connections from the LHb to the VTA, the back projection from the VTA to the LHb, and the direct and indirect projections from the LHb to the VTA were analyzed in the rat. Anterograde and especially retrograde tracing in combination with immunocytochemistry and in-situ hybridization experiments of markers for individual transmitter systems disclosed that most neurons in the LHb were glutamatergic and their axons mainly terminated on GABAergic neurons of the ventral midbrain. Anterior and posterior parts of the VTA and the rostromedial tegmental nucleus (RMTg) receive topographically distinct afferents from the LHb. The back projection from the VTA to the LHb is not predominantly GABAergic, as thought previously, but dopaminergic neurons in the VTA substantially contribute to this pathway. The habenula often is considered as relay station for a reciprocal link between limbic and midbrain areas, while it is not clear, whether these connections are unequivocally reciprocal. Our data indicate that this actually is the case. Furthermore, we have shown that there are two pathways from the LHb to the VTA: a direct projection from the LHb to the VTA and an indirect one from the LHb via the RMTg to the VTA, which may subserve different biological purposes.