Modulation of cellular and synaptic variability in the lamprey spinal cord.
Variability is increasingly recognized as a characteristic feature of cellular, synaptic, and network properties. While studies have traditionally focused on mean values, significant effects can result from changes in variance. This study has examined cellular and synaptic variability in the lamprey spinal cord and its modulation by the neuropeptide substance P. Cellular and synaptic variability differed in different types of cell and synapse. Substance P reduced the variability of subthreshold locomotor-related depolarizations and spiking in motor neurons during network activity. These effects were associated with a reduction in the variability of spiking in glutamatergic excitatory network interneurons and with a reduction in the variance of excitatory interneuron-evoked excitatory postsynaptic potentials (EPSPs). Substance P also reduced the variance of postsynpatic potentials (PSPs) from crossing inhibitory and excitatory interneurons, but it increased the variance of inhibitory postsynpatic potentials (IPSPs) from ipsilateral inhibitory interneurons. The effects on the variance of different PSPs could occur with or without changes in the PSP amplitude. The reduction in the variance of excitatory interneuron-evoked EPSPs was protein kinase A, calcium, and N-methyl-d-aspartate (NMDA) dependent. The NMDA dependence suggested that substance P was acting postsynaptically. This was supported by the reduced variability of postsynaptic responses to glutamate by substance P. However, ultrastructural analyses suggested that there may also be a presynaptic component to the modulation, because substance P reduced the variability of synaptic vesicle diameters in putative glutamatergic terminals. These results suggest that cellular and synaptic variability can be targeted for modulation, making it an additional source of spinal cord plasticity.
Parker
David
D
Department of Physiology, Development, and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. djp27@cam.ac.uk
Bevan
Sarah
S
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D053444:Inhibitory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D007395:Interneurons / Q000187:drug effects / Q000502:physiology; D008124:Locomotion / Q000187:drug effects / Q000502:physiology; D008297:Male; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D009415:Nerve Net / Q000187:drug effects / Q000502:physiology*; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D048428:Petromyzon / Q000033:anatomy & histology / Q000502:physiology*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000378:metabolism; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000187:drug effects / Q000502:physiology; D013373:Substance P / Q000378:metabolism / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism
D018690:Excitatory Amino Acid Agonists; D016194:Receptors, N-Methyl-D-Aspartate; D013373:Substance P; D018698:Glutamic Acid; D017868:Cyclic AMP-Dependent Protein Kinases