A central pattern generator producing alternative outputs: Pattern, strength, and dynamics of premotor synaptic input to leech heart motor neurons

被引:26
作者
Norris, Brian J.
Weaver, Adam L.
Wenning, Angela
Garcia, Paul S.
Calabrese, Ronald L.
机构
[1] Emory Univ, Dept Biol, Atlanta, GA 30322 USA
[2] California State Univ, Dept Biol Sci, San Marcos, CA USA
关键词
D O I
10.1152/jn.00877.2007
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
The central pattern generator (CPG) for heartbeat in medicinal leeches consists of seven identified pairs of segmental heart interneurons and one unidentified pair. Four of the identified pairs and the unidentified pair of interneurons make inhibitory synaptic connections with segmental heart motor neurons. The CPG produces a side-to-side asymmetric pattern of intersegmental coordination among ipsilateral premotor interneurons corresponding to a similarly asymmetric fictive motor pattern in heart motor neurons, and asymmetric constriction pattern of the two tubular hearts, synchronous and peristaltic. Using extracellular recordings from premotor interneurons and voltage-clamp recordings of ipsilateral segmental motor neurons in 69 isolated nerve cords, we assessed the strength and dynamics of premotor inhibitory synaptic output onto the entire ensemble of heart motor neurons and the associated conduction delays in both coordination modes. We conclude that premotor interneurons establish a stereotypical pattern of intersegmental synaptic connectivity, strengths, and dynamics that is invariant across coordination modes, despite wide variations among preparations. These data coupled with a previous description of the temporal pattern of premotor interneuron activity and relative phasing of motor neuron activity in the two coordination modes enable a direct assessment of how premotor interneurons through their temporal pattern of activity and their spatial pattern of synaptic connectivity, strengths, and dynamics coordinate segmental motor neurons into a functional pattern of activity.
引用
收藏
页码:2992 / 3005
页数:14
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