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RP5 is a cell in the right Aplysia californica pedal ganglion.

Basic Information

  • Aliases - Int XIII, Input I, RC1. (Kandel et al. 1967; Parnas et al. 1974; Schlapfer et al. 1976).
  • Neurotransmitters - ACh (activated by or releasing) (Stinakre, 1970; Woodson and Schlapfer, 1979).

This cell was originally named Int XIII as an unidentified cell by Kandel et al, 1967. It was renamed RP5 by Romanova et al. 2007 for it's connection to R15.

Figure 1. Schematic representation of the right pedal ganglion of Aplysia Californica, highlighting RP5 soma and axon projections. Modified from Romanova et al. 2007.
Figure 2. RP5 and it's connections to R15 and L40. A RP5 stimulation causes an EPSP in R15. B and C L40 excitation of R15 is mediated by RP5. B L40 stimulation causes RP5 to elicit R15 stimulation. C Inhibition of RP5 blocks L40 excitation of R15. Modified from Romanova et al. 2007.



RP5's soma is located in sector II of the right Aplysia pedal ganglia, in the deepest cortex layer, superficial to the neuropil. One of it's axons extends through the right pleural ganglion to the right side of the abdominal ganglion (Romanova et al. 2007). Other axonal projections have not been well explored.


When stimulated with current injection, RP5 is known to fire a large EPSP in R15 (Fig. 2a and b). Hyperpolarization of RP5 can then eliminate this EPSP (Fig. 2c). These fictive behaviors are mediated by L40 (Romanova et al. 2007). RP5 stimulation also elicits a small IPSP in L11 (Segal and Koester 1982). RP5 was shown to fire out of phase with L11 during fictive locomotory contraction (Fig. 3) (Romanova et al. 2007). RP5 is shown to be excited by CC5 and fires out of phase with it in fictive locomotion (Xin et al. 1996).


1. Kandel, E.R., Frazier, W.T.,Coggeshall, R.E. (1967). Direct and common connections among identified neruons in Aplysia. J. Neurophysiol. 30. 1352-1376.

2. Parnas, I.,Armstrong, D., Strumwasser, F. (1974). Prolonged excitatory and inhibitory synaptic modulation of a bursting pacemaker neuron. J. Neurophysiol. 37. 594-608.

3. Schlapfer, W. T., Tremblay, J.P., Woodson, P.B., and Barondes, S.H. (1976). Frequency facilitation and post-tetanic potentiation of a unitary synaptic potential in Aplysia californica are limited by different processes. Brain Res. 109. 1-20.

4. Segal, M. M. and Koester, J. (1982). Convergent cholinergic neurons produce similar post-synaptic actions in Aplysia: implications for neural organization. J. Neurophysiol. 47. 742-759.

5. Xin, Y., Weiss, K.R., Kupfermann, I. (1996). An identfied interneuron contributes to aspects of six different behaviors in Aplysia. J. Neurosci. 16. 5266-5279.