The pedal neurons of Aplysia punctata.

Abstract

ABSTRACT Three classes of neurons have been identified in the pedal ganglia of Aplysia punctata. The motor neurons, which may be unipolar or bipolar, have the axon passing into one of the pedal nerves and in the case of the bipolars, the other branch entering the pedal commissure. This synapses with neurons on the opposite side, thus providing an integrative link between the ganglia. The interneurons are without axons in the pedal nerves or commissure, although afferent pathways to these cells and the motor neurons occur in the pedal nerves in a variety of combinations. The pathways in the ipsilateral nerves are for the most part excitatory, but inhibitory fibres occur in the posterior pedal nerve. Inhibitory potentials were often obtained in the interneurons by stimulation of the pedal commissure. A second type of coordinative pathway is provided by fibres which enter the CNS in one of the pedal nerves and terminate on neurons in both pedal ganglia.