Morphology and physiology of pleural-to-buccal neurons coordinating defensive retraction with feeding arrest in the pond snail Lymnaea stagnalis.

1. We have studied morphology, physiology and chemistry of a bilateral pair of pleural-to-buccal projecting neurons (PlB cells) of the pond snail Lymnaea stagnalis. Intracellular dye fills revealed axon arborization within neuropiles of ipsilateral pedal and cerebral ganglia, as well as in both buccal ganglia. Terminal axons of the left and right PlBs showed close proximity within the buccal commissure. 2. The left and right PlB neurons have been found electrotonically coupled and, sometimes, generating synchronous spikes. 3. The results show that two PlB cells operate as a single unit, and that paired buccal networks responsible for feeding rhythm are treated by the PlBs as a single target.