Crunelli V, Segal M
Neuroscience. 1985 May;15(1):47-60. doi: 10.1016/0306-4522(85)90122-8.
Extracellular single unit recordings were made in the median raphe nucleus from rats anaesthetized with urethane. Spontaneous firing as well as orthodromic and antidromic responses to stimulation of the fornix and the medial septum were studied. One hundred and twelve units (out of a total of 355) with a regular spontaneous firing rate of 0.2-3 spikes/s were classified as serotonin-containing neurons. Fifty nine of them were antidromically invaded from either the fornix or the medial septum (conduction velocity, 0.8 m/s) and 7 additional neurones from both the fornix and the medial septum. Antidromic action potentials were followed by a period of decreased probability of firing, that was already present below threshold for antidromic invasion, were proportional to the stimulation intensity and had a latency similar to orthodromic inhibition. No preferential topographical distribution within the median raphe nucleus was observed for the serotonin neurones, even those invaded antidromically. Twenty six neurones with a clear-cut anatomical location around the borders of the median raphe nucleus showed a spontaneous rhythmic activity (4-20 spikes/s) characterized by the presence of extremely prolonged silent periods (up to 5 min). Only one of these neurones was invaded antidromically from the medial septum and none from the fornix. Of the remaining non-serotonin neurones, 28 showed a very low firing rate consisting of single action potentials every 10-60 s while 189 had a spontaneous activity of 6-30 spikes/s. Regardless of their firing rate they were all antidromically invaded from the fornix and/or the medial septum and had a conduction velocity of 5 m/s. These experiments demonstrate the electrophysiological heterogeneity of the neuronal population of the median raphe nucleus, the presence of strong projections of both putative serotonin and non-serotonin neurones to the medial septum and, via the fornix, to the hippocampus, and the existence of axonal branching in both types of neurones.
在使用乌拉坦麻醉的大鼠中缝正中核进行细胞外单单位记录。研究了自发放电以及对穹窿和内侧隔刺激的顺行和逆行反应。在总共355个单位中，有112个单位的自发放电频率规律，为0.2 - 3个脉冲/秒，被归类为含5-羟色胺神经元。其中59个从穹窿或内侧隔被逆行激活（传导速度为0.8米/秒），另外7个神经元同时从穹窿和内侧隔被逆行激活。逆行动作电位之后是一段放电概率降低的时期，该时期在逆行激活阈值以下就已存在，与刺激强度成正比，潜伏期与顺行抑制相似。在中缝正中核内，即使是那些被逆行激活的5-羟色胺神经元，也未观察到优先的拓扑分布。26个在中缝正中核边界周围具有明确解剖位置的神经元表现出自发节律性活动（4 - 20个脉冲/秒），其特征是存在极长的静息期（长达5分钟）。这些神经元中只有一个从内侧隔被逆行激活，没有一个从穹窿被逆行激活。在其余的非5-羟色胺神经元中，28个放电频率极低，每10 - 60秒出现一次单动作电位，而189个具有6 - 30个脉冲/秒的自发活动。无论其放电频率如何，它们都从穹窿和/或内侧隔被逆行激活，传导速度为5米/秒。这些实验证明了中缝正中核神经元群体的电生理异质性、假定的5-羟色胺和非5-羟色胺神经元向内侧隔以及通过穹窿向海马的强投射的存在，以及两种类型神经元中轴突分支的存在。
