Johnson S M, Koshiya N, Smith J C
Cellular and Systems Neurobiology Section, Laboratory of Neural Control, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-4455, USA.
J Neurophysiol. 2001 Apr;85(4):1772-6. doi: 10.1152/jn.2001.85.4.1772.
The pre-Bötzinger complex (pre-BötC), a bilaterally distributed network of rhythmogenic neurons within the ventrolateral medulla, has been proposed to be the critical locus for respiratory rhythm generation in mammals. To date, thin transverse medullary slice preparations that capture the pre-BötC have served as the optimal experimental model to study the region's inherent cellular and network properties. We have reduced the thin slices to isolated pre-BötC "islands" to further establish whether the pre-BötC has intrinsic rhythmicity and is the kernel for rhythmogenesis in the slice. We recorded neuron population activity locally in the pre-BötC with macroelectrodes and fluorescent imaging of Ca(2+) activities with Calcium Green-1AM dye before and after excising the island. The isolated island remained rhythmically active with a population burst profile similar to the inspiratory burst in the slice. Rhythmic population activity persisted in islands after block of GABA(A)ergic and glycinergic synaptic inhibition. The loci of pre-BötC Ca(2+) activity imaged in thin slices and islands were similar, and imaged pre-BötC neurons exhibited synchronized flashing after blocking synaptic inhibition. Population burst frequency increased monotonically as extracellular potassium concentration was elevated, consistent with mathematical models consisting entirely of an excitatory network of synaptically coupled pacemaker neurons with heterogeneous, voltage-dependent bursting properties. Our results provide further evidence for a rhythmogenic kernel in the pre-BötC in vitro and demonstrate that the islands are ideal preparations for studying the kernel's intrinsic properties.
前包钦格复合体（pre-BötC）是位于延髓腹外侧的一个双侧分布的节律性神经元网络，被认为是哺乳动物呼吸节律产生的关键部位。迄今为止，包含pre-BötC的薄横断髓质切片标本一直是研究该区域内在细胞和网络特性的最佳实验模型。我们将薄切片进一步简化为分离的pre-BötC“岛”，以进一步确定pre-BötC是否具有内在节律性，以及它是否是切片中节律发生的核心。我们在切除“岛”之前和之后，用宏观电极局部记录pre-BötC中的神经元群体活动，并使用钙绿-1AM染料对Ca(2+)活动进行荧光成像。分离的“岛”仍保持节律性活动，其群体爆发模式与切片中的吸气爆发相似。在阻断GABA(A)能和甘氨酸能突触抑制后，“岛”中的节律性群体活动仍然持续。在薄切片和“岛”中成像的pre-BötC Ca(2+)活动位点相似，并且在阻断突触抑制后，成像的pre-BötC神经元表现出同步闪烁。随着细胞外钾浓度升高，群体爆发频率单调增加，这与完全由具有异质性、电压依赖性爆发特性的突触耦合起搏器神经元兴奋性网络组成的数学模型一致。我们的结果为体外pre-BötC中存在节律发生核心提供了进一步证据，并证明“岛”是研究该核心内在特性的理想标本。
