Large Unit neuron

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Basic Information

This cell produces the largest impulses in the Pedal Nerve 6 (PdN 6) during the ventral flexion phase of the swim motor program. There is one LU neuron in each Pedal Ganglion. It projects its primary axon to the contralateral Pedal Ganglion through PdN 6 (i.e. the pedal-pedal commissure). LU neurons fire during the ventral phase of the swim motor pattern. Because of this, the impulses of LU neuron recorded from PdN 6 are often used as an indicator for the ventral phase of the swim motor pattern.

Identification

Anatomy:

  • The cell body is located on the anterior edge of the Pedal Ganglion, just on the ventral side near the Pedal Nerve 1.
  • The cell body is translucent and fairly large (60-100 micron in diameter). It may contain spots of orange pigment.
  • The primary axon is very thick. It projects through PdN 6 to the contralateral Pedal Ganglion, and potentially to the contralateral Cerebral Ganglion.

Electrophysiology:

  • Fires in ventral phase of the swim motor pattern.

LU and VSI swim.jpg


  • LU neurons always produce orthodromic impulses in PdN 6, even though VSI-B impulses are coming from the opposite side.
  • VSI-B makes an excitatory synaptic contacts onto the LU neurons of both side.

VSI to LU synapse.jpg

  • The thick axon in PdN 6 can be easily poked with a microelectrode.