Functional characteristics of an identified pair of neurones in the CNS of the pond snail (Lymnaea stagnalis L.).

The properties of 2 giant electrically coupled neurones (A10 and P1) identified in the visceral and right parietal ganglia of Lymnaea stagnalis were examined. The active and passive electrical parameters of the neurones, as well as the junction between them were measured. The main peripheral and interneuronal connections of the neurones were demonstrated using both electrophysiological and morphological methods. It is shown that the coupled cells are not neurones of the same function, but they are asymmetrical ones. This finding is supported by the following results: (1) the axonal pathways of neurones A10 and P1 are different; (2) there are significant differences in their afferent and efferent connections; (3) though the electrical junction between them is bidirectional, the junctional electrical characteristics prefer P1-A10 transmission. According to the electron microscopic results both neurones are possible neurosecretory cells. The differences demonstrated between the 2 giant neurones may have significance concerning their role in a special neuronal network.