Castro-Alamancos M A
Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec H3A 2B4, Canada.
J Neurosci. 2000 Dec 15;20(24):9195-206. doi: 10.1523/JNEUROSCI.20-24-09195.2000.
During disinhibition, the neocortex generates synchronous activities. Block of GABA(A) receptors in neocortex transforms cortical slow-wave oscillations into large-amplitude approximately 1 Hz discharges consisting of a negative spike or multiple negative spikes riding on a positive wave. Further block of GABA(B) receptors in neocortex slows the discharges to approximately 0.5 Hz and increments the number of negative spikes forming rhythmic approximately 10 Hz neocortical oscillations. Although the thalamus responds robustly to these neocortical discharges, these are unaffected by thalamic inactivation using tetrodotoxin. Thus, an important problem relates to the origin of these activities within the neocortex. Current source density analysis and intracellular recordings revealed that the first negative spike in a discharge corresponded to a current sink that reflected a paroxysmal depolarizing shift (PDS) and could originate in the lower layers or in the upper layers. Regardless of the origin (upper or lower layer), the initial current sink always spreads to the same site in upper layer V-IV. In contrast, the approximately 10 Hz oscillation that follows the initial negative spike corresponds to current sinks that always originate in the lower layers but do not spread to upper layer V-IV, jumping directly to the upper layers. Each current sink in the approximately 10 Hz oscillation reflects a small PDS and is followed by a current source that reflects the repolarization after each PDS.
在去抑制过程中，新皮层会产生同步活动。阻断新皮层中的GABA(A)受体会将皮层慢波振荡转变为大约1赫兹的大幅度放电，其由一个负尖峰或多个负尖峰叠加在一个正波上组成。进一步阻断新皮层中的GABA(B)受体会使放电频率减慢至大约0.5赫兹，并增加形成节律性大约10赫兹新皮层振荡的负尖峰数量。尽管丘脑对这些新皮层放电有强烈反应，但这些放电不受使用河豚毒素使丘脑失活的影响。因此，一个重要的问题涉及这些活动在新皮层内的起源。电流源密度分析和细胞内记录显示，放电中的第一个负尖峰对应于一个电流汇，该电流汇反映了阵发性去极化偏移（PDS），并且可能起源于下层或上层。无论起源于上层还是下层，初始电流汇总是扩散到上层V-IV中的同一位置。相比之下，跟随初始负尖峰的大约10赫兹振荡对应于总是起源于下层但不扩散到上层V-IV、而是直接跳转到上层的电流汇。大约10赫兹振荡中的每个电流汇反映一个小的PDS，随后是一个反映每个PDS后复极化的电流源。
