Tong Z Y, Overton P G, Martinez-Cué C, Clark D
Department of Psychology, University of Wales, Swansea, UK.
Exp Brain Res. 1998 Feb;118(4):466-76. doi: 10.1007/s002210050303.
It is rapidly becoming apparent that the prefrontal cortex (PFC) plays a major role in controlling the activity of midbrain dopaminergic (DA) neurons. We have previously demonstrated that electrical stimulation of the PFC elicits inhibition-excitation (IE) and excitation (E) activity patterns in DA neurons in the ventral tegmental area (VTA; A10 cell group). Since non-DA neurons in the VTA are cortically innervated, synapse upon DA neurons and appear to have an inhibitory impact, we determined the extent to which the responses of these neurons to stimulation of the PFC could account for the responses seen in DA neurons upon cortical stimulation. Stimulation of the PFC (0.25 mA and 1.0 mA) elicited three categories of response in the majority of VTA non-DA neurons. Types I and II were characterised by a short-to-moderate latency excitation (referred to as "early excitations"), in the latter case preceded by inhibition. Type III responses consisted of inhibition in the absence of an early excitation. Elements of these responses were compared with the temporal characteristics of key elements of responses elicited in DA neurons by PFC stimulation. Although the early excitations in non-DA neurons preceded the inhibitions in DA neurons exhibiting IE responses, the early excitations began approximately 100 ms before the inhibitions in DA neurons and often ended several tens of milliseconds before the inhibitions began, making a causal relationship between these events unlikely. The inhibitions in Type III responses, combined with the inhibitions which followed the early excitations in many Type I and II responses, showed temporal characteristics that suggested a possible causal relationship with the excitations in DA neurons exhibiting E responses, but not those exhibiting IE responses. However, since the excitatory phases of E and IE responses appear to be homologous, the lack of involvement of non-DA neurons in the excitatory phase of IE responses tends to cast doubt on the involvement of non-DA neurons in the excitation during E responses. In fact, the most coherent impression that emerges is that non-DA neurons in the VTA do not influence the activity of A10 DA neurons on a short time-scale (i.e. phasically), but instead may influence activity on a longer time-scale (i.e. tonically).
前额叶皮层（PFC）在控制中脑多巴胺能（DA）神经元的活动中发挥着主要作用，这一点正迅速变得明显。我们之前已经证明，对PFC进行电刺激会在腹侧被盖区（VTA；A10细胞群）的DA神经元中引发抑制-兴奋（IE）和兴奋（E）活动模式。由于VTA中的非DA神经元接受皮层神经支配，与DA神经元形成突触，并且似乎具有抑制作用，我们确定了这些神经元对PFC刺激的反应在多大程度上可以解释DA神经元在皮层刺激时所观察到的反应。对PFC（0.25 mA和1.0 mA）的刺激在大多数VTA非DA神经元中引发了三类反应。I型和II型的特征是具有短至中等潜伏期的兴奋（称为“早期兴奋”），在后一种情况下，兴奋之前有抑制。III型反应由无早期兴奋时的抑制组成。将这些反应的成分与PFC刺激在DA神经元中引发的反应的关键成分的时间特征进行了比较。尽管非DA神经元中的早期兴奋先于表现出IE反应的DA神经元中的抑制，但早期兴奋在DA神经元中的抑制开始前约100毫秒开始，并且常常在抑制开始前几十毫秒结束，使得这些事件之间不太可能存在因果关系。III型反应中的抑制，与许多I型和II型反应中早期兴奋之后的抑制相结合，显示出的时间特征表明与表现出E反应的DA神经元中的兴奋可能存在因果关系，但与表现出IE反应的DA神经元中的兴奋不存在因果关系。然而，由于E反应和IE反应的兴奋阶段似乎是同源的，非DA神经元未参与IE反应的兴奋阶段往往使人怀疑非DA神经元在E反应期间的兴奋中是否起作用。事实上，最一致的印象是，VTA中的非DA神经元在短时间尺度上（即相位上）不影响A10 DA神经元的活动，而是可能在较长时间尺度上（即紧张性地）影响活动。
