Straub Volko A, Staras Kevin, Kemenes György, Benjamin Paul R
Sussex Centre for Neuroscience, School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom.
J Neurophysiol. 2002 Oct;88(4):1569-83. doi: 10.1152/jn.2002.88.4.1569.
Understanding central pattern generator (CPG) circuits requires a detailed knowledge of the intrinsic cellular properties of the constituent neurons. These properties are poorly understood in most CPGs because of the complexity resulting from interactions with other neurons of the circuit. This is also the case in the feeding network of the snail, Lymnaea, one of the best-characterized CPG networks. We addressed this problem by isolating the interneurons comprising the feeding CPG in cell culture, which enabled us to study their basic intrinsic electrical and pharmacological cellular properties without interference from other network components. These results were then related to the activity patterns of the neurons in the intact feeding network. The most striking finding was the intrinsic generation of plateau potentials by medial N1 (N1M) interneurons. This property is probably critical for rhythm generation in the whole feeding circuit because the N1M interneurons are known to play a pivotal role in the initiation of feeding cycles in response to food. Plateau potential generation in another cell type, the ventral N2 (N2v), appeared to be conditional on the presence of acetylcholine. Examination of the other isolated feeding CPG interneurons [lateral N1 (N1L), dorsal N2 (N2d), phasic N3 (N3p)] and the modulatory slow oscillator (SO) revealed no significant intrinsic properties in relation to pattern generation. Instead, their firing patterns in the circuit appear to be determined largely by cholinergic and glutamatergic synaptic inputs from other CPG interneurons, which were mimicked in culture by application of these transmitters. This is an example of a CPG system where the initiation of each cycle appears to be determined by the intrinsic properties of a key interneuron, N1M, but most other features of the rhythm are probably determined by network interactions.
要理解中枢模式发生器（CPG）电路，需要详细了解组成神经元的内在细胞特性。由于与电路中其他神经元相互作用所导致的复杂性，大多数CPG中的这些特性尚未得到充分理解。在蜗牛椎实螺的摄食网络中也是如此，它是特征最明显的CPG网络之一。我们通过在细胞培养中分离出构成摄食CPG的中间神经元来解决这个问题，这使我们能够研究它们基本的内在电生理和药理细胞特性，而不受其他网络组件的干扰。然后将这些结果与完整摄食网络中神经元的活动模式联系起来。最引人注目的发现是内侧N1（N1M）中间神经元能内在地产生平台电位。这一特性可能对整个摄食回路中的节律产生至关重要，因为已知N1M中间神经元在响应食物时启动摄食周期中起关键作用。另一种细胞类型腹侧N2（N2v）中的平台电位产生似乎取决于乙酰胆碱的存在。对其他分离出的摄食CPG中间神经元[外侧N1（N1L）、背侧N2（N2d）、相位性N3（N3p）]和调制性慢振荡器（SO）的研究表明，它们在模式产生方面没有显著的内在特性。相反，它们在回路中的放电模式似乎很大程度上由来自其他CPG中间神经元的胆碱能和谷氨酸能突触输入决定，在培养中通过应用这些递质可模拟这些输入。这是一个CPG系统的例子，其中每个周期的启动似乎由关键中间神经元N1M的内在特性决定，但节律的大多数其他特征可能由网络相互作用决定。
