Differential channeling of sensory stimuli onto a motor neuron in the leech.
We studied a specific sensory-motor pathway in the isolated leech ganglia. Pressure-sensitive mechanosensory neurons were stimulated with trains of action potentials at 5-20 Hz while recording the responses of the annulus erector motorneurons that control annuli erection. The response of the annulus erector neurons was a succession of excitatory postsynaptic potentials followed by inhibitory postsynaptic potentials. The excitatory postsynaptic potentials had a brief time-course while the inhibitory postsynaptic potentials had a prolonged time-course that enabled their temporal summation. Thus, the net effect of pressure-sensitive neuron stimulation on the annulus erector neurons was inhibitory. Both phases of the response were mediated by chemical transmission; the excitatory postsynaptic potentials were transmitted via a monosynaptic pathway, and the inhibitory postsynaptic potentials via a polysynaptic one. The pattern of expression of this dual response depended on the field of innervation of the sensory neuron and it was under the influence of cell 151, a non-spiking interneuron, that could regulate the expression of the hyperpolarization. The interaction between pressure-sensitive neurons and annulus erector neuron reveals how sensory specificity, connectivity pattern and regulatory elements interplay in a specific sensory-motor network.
Iscla
I
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Dto de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Capital Federal, Argentina.
Arini
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PD
Szczupak
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L
D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D004558:Electric Stimulation; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000502:physiology; D066298:In Vitro Techniques; D007865:Leeches / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009046:Motor Neurons / Q000378:metabolism / Q000502:physiology*; D009434:Neural Pathways / Q000378:metabolism / Q000502:physiology; D009475:Neurons, Afferent / Q000378:metabolism / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010812:Physical Stimulation; D011312:Pressure