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P3 is a motor neuron in the Aplysia californica pedal ganglia.

Figure 1. Schematic representation of the dorsal Aplysia pedal and pleural ganglia. Left pedal ganglion shows designated sectors, right pedal ganglion shows approximate locations of identified neurons. Identified motor neuron P3 is shown at lateroanterior portion of sector II. Modified from Hening et al 1979.

Basic Information

  • No known alias
  • Neurotransmitter is as yet unidentified



P3 is a 80-120um cell, and is lightly pigmented. It is located on the medioanterior pedal ganglion, adjacent to the cerebropedal connective in sector II, usually adjacent to P2. Like P2, P3 is considered to be a transverse contractor motor neuron, with innervation to the mesosegments of the Aplysia californica foot (Hening et al. 1979)


Figure 2. Simultaneous recordings of motor neurons P2 and P3 in intact (A) and isolated (B) preparations. Stimulation to "left posterior pedal nerve" (no other identification given) indicated by bars causes cyclic motor bursting in P2 preceding P3 in intact animals and isolated CNS in a similar manner. Modified from Hening et al 1979.

When stimulated in intact animals, P3 causes a large contraction dorsoventrally in the second, third, and fourth teguments. P3 is considered to be one of the mesosegmental motor neurons.While the animal is moving, P3 receives both depolarizing and hyperpolarizing stimuli, similar to that observed in P2. It is known to send axons to pedal ganglion nerve Pd9 (Hening et al. 1979).


1. Hening, W.A., Walters, E.T., Carew, T.J., Kandel, E.R. (1979) Motorneuronal control of locomotion in Aplysia. Brain Research, 179. 231-253.