Deschênes M, Paradis M, Roy J P, Steriade M
J Neurophysiol. 1984 Jun;51(6):1196-219. doi: 10.1152/jn.1984.51.6.1196.
Intracellular and extracellular recordings were performed in lateral thalamic nuclei (ventroanterior-ventrolateral, ventroposterolateral, centralis, lateralis, and reticularis) of cats under barbiturate anesthesia. Neurons were driven antidromically and/or synaptically by stimulating cortical projection areas and prethalamic afferent pathways. Three neuronal populations were identified on the basis of electrophysiological and anatomical criteria: thalamic relay neurons, local interneurons, and reticularis thalami neurons. At rest, two coexistent rhythms were observed in thalamic neurons. Brief episodes (1-2 s) of membrane-potential oscillations at frequencies of 8-12 Hz appeared with a periodicity of about 10 s. In relay neurons, each episode was characterized by a sequence of hyperpolarizations and burst discharges. These rhythmic episodes of hyperpolarization recurring about every 10 s could be reversed in sign by hyperpolarizing currents or by Cl injection, hence suggesting that they were mainly composed of rhythmic inhibitory postsynaptic potentials (IPSPs). This result also indicated that the slow 0.1-Hz rhythm was imposed on relay neurons by other neuronal pools. Following a complete isolation of the thalamus by cortical and high brain stem lesions, the slow 0.1-Hz rhythm was still present, and it was concluded that this rhythm was generated within the thalamus by inhibitory elements. In thalamic interneurons (identified by electrophysiological criteria) brief episodes (1-2 s) of repetitive depolarizations (8-12 Hz) and burst discharges recurred every 10 s. In the interval, the membrane potential of interneurons slowly hyperpolarized, contrasting with the rhythmic phasic hyperpolarizations observed in relay neurons. Electrophysiological properties shared by most relay neurons included a) afterspike hyperpolarizing potentials of long duration, which were blocked by injections of a Ca chelator; b) a pacemaker potential in the vicinity of the spike trigger level; and c) a low-threshold somatic Ca conductance that underlies burst discharges. As a general rule, prethalamic volleys induced faster rising and shorter lasting EPSPs than cortical volleys. Moreover prethalamic afferent-evoked responses could be associated with production of fast prepotentials, some of which appeared to result from dendritic spiking. It appears that synaptic and intrinsic membrane properties of thalamic neurons allow them to function under two modes: a relay mode and an oscillatory mode; the oscillatory mode being intrinsic to the thalamus and the relay mode being commanded and maintained by cortical and brain stem structures.
在巴比妥类麻醉下，对猫的外侧丘脑核（腹前 - 腹外侧、腹后外侧、中央、外侧和网状核）进行细胞内和细胞外记录。通过刺激皮层投射区和丘脑前传入通路，以逆向和/或突触方式驱动神经元。根据电生理和解剖学标准，确定了三类神经元群体：丘脑中继神经元、局部中间神经元和丘脑网状核神经元。在静息状态下，丘脑神经元中观察到两种共存的节律。频率为8 - 12Hz的膜电位振荡的短暂发作（1 - 2秒）以约10秒的周期出现。在中继神经元中，每个发作的特征是一系列超极化和爆发性放电。这种每隔约10秒重复出现的超极化节律性发作，可通过超极化电流或注射氯离子而使信号反转，因此表明它们主要由节律性抑制性突触后电位（IPSPs）组成。这一结果还表明，0.1Hz的慢节律是由其他神经元群强加于中继神经元的。在通过皮层和高位脑干损伤使丘脑完全隔离后，0.1Hz的慢节律仍然存在，由此得出结论，这种节律是由丘脑内的抑制性元件产生的。在丘脑中间神经元（根据电生理标准确定）中，重复去极化（8 - 12Hz）和爆发性放电的短暂发作（1 - 2秒）每隔10秒重复出现。在此间隔期间，中间神经元的膜电位缓慢超极化，这与在中继神经元中观察到的节律性相位超极化形成对比。大多数中继神经元共有的电生理特性包括：a）长时间的锋后超极化电位，可被注射钙螯合剂阻断；b）在锋触发水平附近的起搏电位；c）构成爆发性放电基础的低阈值体细胞钙电导。一般来说，丘脑前冲动诱发的兴奋性突触后电位（EPSPs）上升更快且持续时间更短，比皮层冲动诱发的EPSPs更明显。此外，丘脑前传入诱发的反应可能与快速前电位的产生有关，其中一些似乎是由树突棘突引起的。看来，丘脑神经元的突触和内在膜特性使它们能够在两种模式下发挥作用：中继模式和振荡模式；振荡模式是丘脑固有的，中继模式则由皮层和脑干结构控制和维持。
