Chapter

Modulation of Lamprey Locomotor Circuit

A. El Manira

in Handbook of Brain Microcircuits

Published on behalf of Oxford University Press

Published in print August 2010 | ISBN: 9780195389883
Published online September 2012 | e-ISBN: 9780199965137 | DOI: http://dx.doi.org/10.1093/med/9780195389883.003.0034
Modulation of Lamprey Locomotor Circuit

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The spinal circuitry produces the basic motor pattern underlying locomotion and is also capable of acting as a processing interface to adjust the motor output to descending inputs from the brain and sensory feedback. In the lamprey, the detailed information available on the organization of the locomotor network has facilitated the assessment of the role of different modulatory systems. Each hemisegment of the spinal cord contains a network of excitatory interneurons that drive the activity of motoneurons and generate rhythmic bursting, while inhibitory commissural interneurons are responsible for the left–right alternation. These components are responsible for the cycle-to-cycle operation, while a number of modulatory systems regulate the membrane properties of individual network neurons and/or the synaptic properties and thus contribute to generation of the locomotor activity. This modulation primarily involves activation of G protein-coupled metabotropic receptors. It can be intrinsic, mediated by transmitters released from network neurons during ongoing locomotor activity such as glutamate activating the family of metabotropic glutamate receptors (mGluRs). Extrinsic modulation is mediated by transmitters released from neurons that are not part of the network that activate, for instance, 5-HT, dopamine, GABA, or tachykinin receptors. These intrinsic and extrinsic modulatory systems play a fundamental role in the basic network function and in the induction of short-term (seconds or minutes) or long-term (hours or days) plasticity of the locomotor circuit activity. This chapter summarizes the influence of some of these modulatory systems on the global output of the network and the underlying cellular and synaptic mechanisms.

Chapter.  3683 words.  Illustrated.

Subjects: Development of the Nervous System

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