Glenn L L, Steriade M
J Neurosci. 1982 Oct;2(10):1387-404. doi: 10.1523/JNEUROSCI.02-10-01387.1982.
Spontaneous firing and antidromically or synaptically evoked discharges of 89 single neurons in centralis lateralis-paracentralis (CL-Pc) intralaminar thalamic nuclei were examined during waking and sleep states in behaving cats with chronic pontine lesions. Twenty-four neurons were activated synaptically at short latencies from the midbrain reticular formation (MRF) after anterograde degeneration of passing fibers. Sixty-five neurons were identified antidromically as projecting to motor or parietal association cortical areas; of them, 23 also could be excited synaptically from the MRF. These neurons were regarded as possibly being involved in the transfer toward the neocortex of the tonic excitation from the MRF during EEG-desynchronized behavioral states. Rates of spontaneous discharge in CL-Pc neurons doubled from synchronized sleep (S) to either wakefulness (W) or desynchronized sleep (D). First order measures of discharge patterns indicated that interval modes in both W and D states (greater than 10 msec) are significantly different from those in S (2.5 msec). During S, the intervals found in the less than 5-msec class indicated the intraburst frequencies; a later minor mode (200 to 350 msec) reflected the interburst silent periods. All neurons tested for antidromic activation from cortical areas had enhanced responsiveness in both W and D states as compared to S sleep. In some cases, the enhanced antidromic excitability was observed in conjunction with a transformation from initial segment spikes during S to full spikes in EEG-desynchronized states. During both W and D states, compared to S sleep, the probability of monosynaptically elicited single discharges to MRF stimulation was increased, and the latency and duration of high frequency bursts evoked by MRF volleys were shortened. We conclude that the features of cortically projecting intralaminar neurons that relay MRF activity fit in well with their hypothesized role in the tonic activation processes that characterize both W and D states. Several lines of evidence suggest that sustained hyperpolarization prevails in intralaminar neurons during S sleep. This is the basic prerequisite for thalamic bursting. The effect of long lasting inhibitory potentials in thalamic neurons provides a mechanism for closing sensory channels during S sleep.
在患有慢性脑桥损伤的行为猫的清醒和睡眠状态下，对中央外侧 - 旁中央（CL - Pc）层内丘脑核中89个单神经元的自发放电以及逆行或突触诱发放电进行了研究。在经过的纤维顺行性变性后，有24个神经元在短潜伏期从脑桥网状结构（MRF）突触激活。65个神经元被逆向鉴定为投射到运动或顶叶联合皮质区域；其中23个也可从MRF突触兴奋。这些神经元被认为可能在脑电图去同步化行为状态期间参与将来自MRF的紧张性兴奋向新皮质的传递。CL - Pc神经元的自发放电率从同步睡眠（S）到清醒（W）或去同步睡眠（D）增加了一倍。放电模式的一级测量表明，W和D状态（大于10毫秒）的间隔模式与S状态（2.5毫秒）有显著差异。在S期间，小于5毫秒类别的间隔表示爆发内频率；稍后的一个较小模式（200至350毫秒）反映了爆发间沉默期。所有测试从皮质区域进行逆向激活的神经元在W和D状态下与S睡眠相比反应性增强。在某些情况下，观察到增强的逆向兴奋性与从S期间的起始节段棘波到脑电图去同步化状态下全棘波的转变同时发生。在W和D状态下，与S睡眠相比，对MRF刺激单突触诱发单个放电的概率增加，并且MRF volley诱发的高频爆发的潜伏期和持续时间缩短。我们得出结论，传递MRF活动的皮质投射层内神经元的特征与其在表征W和D状态的紧张性激活过程中的假设作用非常吻合。几条证据表明，在S睡眠期间层内神经元中持续的超极化占主导。这是丘脑爆发的基本前提。丘脑神经元中持久抑制电位的作用为在S睡眠期间关闭感觉通道提供了一种机制。
