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CPG neurons' cell somata were cultured in vitro with RPeD11 to foster neuron growth and synaptic connectivity. The images show synaptic connections developed between RPeD11 and RPeD1 (top), VD4 (middle), and IP3I (bottom). Source: T. Inoue et al. (1996).

L/RPeD11 are neurons in Lymnaea stagnate.

L/RPeD11 neuron

Left and right pedal dorsal 11 (L/RPeD11) neurons are a pair of bilateral internerons that form electrical connections with the foot and body wall of the Lymnaea stagnate. They coordinate locomotor motoneurons and play a key role in whole-body withdrawal. They are also involved in regulating respiratory behavior through chemical connections with heart motoneurons.


The ring of nine ganglia of the Lymnaea central nervous system which are encircled by L/RPeDll neurons. Abbreviations: C, cerebral ganglion; Pa, parietal ganglion; Pe, pedal ganglion; Pl, pleural ganglion; V, visceral ganglion. Source: Benjamin, P.R. (2008).
The L/RPeDll neurons are located on the dorsal surface of the left and right pedal ganglia, respectively, with cell bodies located at the pedal end of in front of the statocyst. They are electrically coupled to each other and have similar structures. They are the largest cells in the pedal G clusters with cell bodies measuring 30-50/an in diameter. They encircle the lower ganglionic ring and enter the cerebral ganglia.

Projections from L/RPeD11 have branches in many ganglia, i.e. pedal, pleural, parietal and visceral. Extensive axonal arborizations of LPeDll and RPeDll are found in neuropile areas where somata or axonal branches of L/RPeG cluster and where visceral H, I, J and K cells are located.

LPeDll has two main axons, one running ipsilaterally and the other contralaterally, which have 3 projections:

  1. Right superior cervical nerve (RSCN) which stems from the right pedal ganglion
  2. Anal nerves (AN)
  3. External parietal nerves (EPN)

RPeD11 projects to the periphery via:

  1. Intestinal nerves (IN)
  2. Anal nerves (AN)
  3. Cutaneous pallial nerves (CPN)

Molecular profile

Neurotransmitter: Glutamate


In this schematic drawing, L/RPeD11 are shown located in the left and right dorsal surface of the pedal ganglia, respectively. Source: Syed NI, Winlow W. (1991).
Electrical Connections
L/RPeDll are electrically coupled to each other and to locomotor and body wall motoneurones:
  1. L/RPeDll neurons form electrical connections to motoneurons to the foot found in L/RPeG clusters.
  2. L/RPeDll are also electrically coupled to and coordinate the activities of L/RCeA cluster neurons found in body wall musculature.

Chemical Connections
In addition, L/RPeDll form chemical connections to modulate cardiorespiratory action with appropriate motoneurons.

  1. L/RPeDll inhibit VJ cells, cells that are part of the visceral ganglion which activate the pneumostome opener muscle (expiration).
  2. They excite VK cells which activate the pneumostome closer muscle (inspiration).
  3. L/RPeDll and all their electrically coupled follower cells are inhibited by a respiratory interneurone involved in pneumostome closure (visceral dorsal 4).
  4. They excite a pair of electrically coupled neurones, visceral dorsal 1 and right parietal dorsal 2, which are sensitive to changes in the partial pressure of environmental oxygen.


The L/RPeD11 neurons are critical in the survival of the Lymnaea as they synchronize contraction of body wall and foot muscles with cessation of locomotion and respiratory activity during the animal’s escape response. This multifunctional role involves (1) coordinating motor behavior involved in whole-body withdrawal and (2) integrating cardiorespiratory output with these and other motor behaviors.

Whole-body withdrawal is a defensive response of the Lymnaea during which (1) the head-foot is shortened by the simultaneous action of the dorsal longitudinal muscle (DLM) and the columellar muscle (CM) and (2) the CM pulls the shell down to protect the body. Note that the CM and DLM motoneurons are widely distributed across the Lymnaea’s central nervous system. The L/RPeD11 interneurons are responsible for coordinating the simultaneous action of the DLM and CM during whole-body withdrawal.

In addition to its role in coordinating motor movements during whole-body withdrawal, L/RPeD11 interneurons inhibit both muscular and neuronal components of the respiratory behavior. Since whole-body withdrawal and respiration are incompatible in the Lymnaea, activation of the neurons governing muscle movement must coincide with inhibiting firing of the neurons and muscle movements associated with respiration. L/RPeD11 neurons do this by simultaneously triggering a muscle response in their pneumostome (pulmonary opening) and inhibiting the action of interneuron RPeD1, a critical component of the central pattern generator (CPG) that underlies respiratory behavior.


Benjamin, P.R. (2008) Scholarpedia, 3(1):4124. | Full Text.

Ferguson, GP, Benjamin, PR. (1991) The whole-body withdrawal response of Lymnaea stagnalis. I. Identificaiton of central motoneurones and muscles. J Exp Biol. 1991 Jul; 158:63-95. PMID: 1919418.

Ferguson, GP, Benjamin, PR. (1991) The whole-body withdrawal response of Lymnaea stagnalis. II. Activation of central motoneurones and muscles by sensory input. J Exp Biol. 1991 Jul; 158:63-95. PMID: 1919419.

Inoue, T., Takasaki, M., Lukowiak, K., Syed, I. (1996) Inhibition of the respiratory pattern-generating neurons by an identified whole-body withdrawal interneuron of Lymnaea stagnalis. J Exp Biol. 1996; 199: 1887–1898. PMID: 9319800.

Nesic, O.B., Magoski, N.S., McKenney, K.K., Syed, N.I., Lukowiak, K. Bulloch, A.G.M. (1996) Glutamate as a putative neurotransmitter in the mollusc, Lymnaea stagnalis. Neuroscience 1996 Dec;75(4):1255-69. PMID: 8938758.

Syed NI, Winlow W. (1991) Coordination of locomotor and cardiorespiratory networks of Lymnaea stagnalis by a pair of identified interneurones. J Exp Biol. 1991 Jul;158:37-62. PMID: 1919413.

Additional information

Scholarpedia article on Lymnaea