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The Journal of Neuroscience, January 15, 2003, 23(2):682-692

Coactivation of Motoneurons Regulated by a Network Combining Electrical and Chemical Synapses

Lorena Rela and Lidia Szczupak

Laboratorio de Fisiología y Biología Molecular, Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, 1428 Buenos Aires, Argentina

Electrical transmission among neurons has been considered a mechanism to synchronize neuronal activity, and rectification provides a mechanism to confine the flow of signals among the connected neurons. The question is how this type of transmission operates within complex neuronal networks. In the leech, the neurons located in position 151 of the midbody ganglion map are connected to virtually every motoneuron via rectifying electrical synapses that pass negative current to the motoneurons. These are nonspiking neurons, and here we have labeled them NS neurons. The goal of this investigation has been to assess their role in regulating motor activity and how rectifying electrical synapses contribute to the function of motor networks.

The coupling between NS neurons and motoneurons was voltage sensitive: it increased as motoneurons were depolarized. In addition, excitation of motoneurons evoked hyperpolarizing synaptic responses in NS neurons, the amplitude of which depended on the membrane potential of the latter and on the motoneuron firing frequency. This hyperpolarization was mediated by chemical transmission through an interneuronal layer that spanned the nerve cord. These interactions established a feedback loop between NS and motoneurons that was regulated by the membrane potential of NS. This mechanism was responsible for the uncoupling between otherwise electrically coupled motoneurons. In this way, the NS neurons can act as "electrical neuromodulators," modifying the interaction of other neurons, depending on the activity of the system as a whole.

Key words: gap junctions; electrical rectification; rectifying electrical synapses; motor control; leech; nonspiking

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Copyright © 2003 Society for Neuroscience  0270-6474/03/232682-11$05.00/0

This article has been cited by other articles:

				P. S. Garcia, T. M. Wright, I. R. Cunningham, and R. L. Calabrese Using a Model to Assess the Role of the Spatiotemporal Pattern of Inhibitory Input and Intrasegmental Electrical Coupling in the Intersegmental and Side-to-Side Coordination of Motor Neurons by the Leech Heartbeat Central Pattern Generator J Neurophysiol, September 1, 2008; 100(3): 1354 - 1371. [Abstract] [Full Text] [PDF]

				L. Rela and L. Szczupak In Situ Characterization of a Rectifying Electrical Junction J Neurophysiol, February 1, 2007; 97(2): 1405 - 1412. [Abstract] [Full Text] [PDF]

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