期刊
JOURNAL OF NEUROSCIENCE
卷 35, 期 40, 页码 13673-13686出版社
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.2541-15.2015
关键词
motoneuron; quantal analysis; recurrent inhibition; Renshaw cell
资金
- Wellcome Trust [WT088279/A/09/Z]
- Leverhulme Trust [RPG-2013-176]
- Biotechnology and Biological Sciences Research Council [BB/L001454]
- Biotechnology and Biological Sciences Research Council studentship
- Biotechnology and Biological Sciences Research Council [BB/L001454/1, 957459] Funding Source: researchfish
- BBSRC [BB/L001454/1] Funding Source: UKRI
Renshaw cells represent a fundamental component of one of the first discovered neuronal circuits, but their function in motor control has not been established. They are the only central neurons that receive collateral projections from motor outputs, yet the efficacy of the excitatory synapses from single and converging motoneurons remains unknown. Here we present the results of dual whole-cell recordings from identified, synaptically connected Renshaw cell-motoneuron pairs in the mouse lumbar spinal cord. The responses from single Renshaw cells demonstrate that motoneuron synapses elicit large excitatory conductances with few or no failures. We show that the strong excitatory input from motoneurons results from a high probability of neurotransmitter release onto multiple postsynaptic contacts. Dual current-clamp recordings confirm that single motoneuron inputs were sufficient to depolarize the Renshaw cell beyond threshold for firing. Reciprocal connectivity was observed in approximately one-third of the paired recordings tested. Ventral root stimulation was used to evoke currents from Renshaw cells or motoneurons to characterize responses of single neurons to the activation of their corresponding presynaptic cell populations. Excitatory or inhibitory synaptic inputs in the recurrent inhibitory loop induced substantial effects on the excitability of respective postsynaptic cells. Quantal analysis estimates showed a large number of converging inputs from presynaptic motoneuron and Renshaw cell populations. The combination of considerable synaptic efficacy and extensive connectivity within the recurrent circuitry indicates a role of Renshaw cells in modulating motor outputs that may be considerably more important than has been previously supposed.
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