Coactivation of motoneurons regulated by a network combining electrical and chemical synapses

• Autores: Rela, L.; Szczupak, L.
• Año de publicación: 2003
• Idioma: inglés
• Tipo de recurso: artículo
• Fuente: J. Neurosci. 2003;23(2):682-692
• Materia: Electrical rectification; Gap junctions; Leech; Motor control; Nonspiking; Rectifying electrical synapses; animal cell; animal tissue; article; cell synchronization; controlled study; depolarization; excitatory junction potential; feedback system; ganglion; gap junction; hyperpolarization; interneuron; leech; membrane potential; molecular mechanics; motoneuron; nerve cell network; nerve conduction; nerve cord; neuromodulation; neurotransmission; nonhuman; polysynaptic reflex; priority journal; signal transduction; spike; synapse; Action Potentials; Animals; Electric Stimulation; Feedback; Ganglia, Invertebrate; Gap Junctions; Leeches; Membrane Potentials; Motor Neurons; Nerve Net; Neural Inhibition; Neural Pathways; Synapses; Synaptic Transmission
• Institución: Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales

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.
Fil:Rela, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
Fil:Szczupak, L. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.