White F J, Wang R Y
Life Sci. 1984 Mar 19;34(12):1161-70. doi: 10.1016/0024-3205(84)90088-2.
The present experiments investigated the relationship between the spontaneous basal firing rate of A10 dopamine (DA) neurons and their sensitivity to the rate-suppressant effects of intravenously administered apomorphine (APO) and d-amphetamine (AMP) as well as microiontophoretically ejected DA. The results indicated highly significant inverse relationships between basal neuronal activity and sensitivity to DA and DA agonists, i.e. the faster the spontaneous rate of an A10 DA neuron, the less sensitive that cell was to agonist-induced suppression. This relationship was not found for the rate suppressant effects of iontophoretic gamma-aminobutyric acid. There were no significant differences between the effects of iontophoretic DA on pre-glutamate and glutamate-driven activity of the same A10 DA neurons indicating that faster firing rates, per se, did not determine the sensitivity of these cells to DA agonists. Rather, these results suggest that both spontaneous activity and sensitivity to DA agonists may be determined by the density (or sensitivity) of DA autoreceptors on A10 DA neurons. This hypothesis was supported by the finding that antidromically identified mesocortical DA neurons, which were significantly less responsive to DA, APO and AMP exhibited significantly faster firing rates than other A10 DA neurons. Thus, this subpopulation of A10 DA neurons is primarily made up of cells with low autoreceptor density (or sensitivity).
本实验研究了A10多巴胺（DA）神经元的自发基础放电率与其对静脉注射阿扑吗啡（APO）和d-苯丙胺（AMP）以及微量离子电泳释放的DA的速率抑制作用的敏感性之间的关系。结果表明，基础神经元活动与对DA和DA激动剂的敏感性之间存在高度显著的负相关关系，即A10 DA神经元的自发放电速率越快，该细胞对激动剂诱导的抑制作用就越不敏感。对于离子电泳γ-氨基丁酸的速率抑制作用，未发现这种关系。离子电泳DA对同一A10 DA神经元的谷氨酸前体和谷氨酸驱动活动的影响之间没有显著差异，这表明较快的放电速率本身并不能决定这些细胞对DA激动剂的敏感性。相反，这些结果表明，自发活动和对DA激动剂的敏感性可能都由A10 DA神经元上DA自身受体的密度（或敏感性）决定。这一假设得到了以下发现的支持：经逆向鉴定的中皮质DA神经元对DA、APO和AMP的反应明显较弱，其放电速率明显快于其他A10 DA神经元。因此，A10 DA神经元的这一亚群主要由自身受体密度（或敏感性）较低的细胞组成。
