Electronic transmission between giant neurones identified in the CNS or Lymnaea stagnalis.

In the CNS of Lymnaea stagnalis it was verified for two paired cells (A11--A11' and P1--A10) that the interneuronal connection is realized by electronic transmission. The evidences of electrical coupling: 1:1 synchronity of spontaneous activities; the delay of transmission is less than that in the case of a chemical synapse; any neurone can drive the firing of its own coupled pair; the transmission is bidirectional both for depolarization and hyperpolarization. The active and passive electrical constants of the electrical junctions were estimated. The coupling coefficients appeared to be relatively large. The coupling coefficient and the junctional resistance depend on the stimulating current to a high degree. The value of capacity of junction exceeds that of soma, or is equal to it, and is a function of the stimulating current, so the characteristics of the transmission are determined by a variable impedance, rather than by a simple ohmic resistance. The morphological properties of the junctions were examined with light microscope using intracellular CoCl2 staining. It is suggested that cell A11' may be derived from an anomalous duplication of cell A11. The morphological and functional differences between the two paired cells examined are reflected in the detailed properties of the junctions. These differences between the two paired cells examined are reflected in the detailed properties of the junctions. These differences may have a significance concerning the role of the paired cells in the neuronal network.