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Transmission at a ‘direct’ electrical connexion mediated by an interneurone in the leech.
Author(s) -
Muller K J,
Scott S A
Publication year - 1981
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1981.sp013605
Subject(s) - leech , neuroscience , depolarization , coupling (piping) , electrical synapses , receptive field , intracellular , axon , gap junction , ganglion , biophysics , physics , biology , computer science , materials science , microbiology and biotechnology , world wide web , metallurgy
1. Touch sensory neurones in the leech excite a rapidly conducting interneurone called the S‐cell. Although the electrical synaptic connexion between the two cells is monosynaptic by physiological criteria, intracellular staining reveals that the touch cells and the S‐cell do not make contact, but instead are linked by a pair of small interneurones. 2. The electrical coupling between touch cells and S‐cells rectifies, in that depolarizing current but not hyperpolarizing current passes from the touch cell into the S‐cell. The rectifying junction is between the touch cells and coupling interneurones, while the connexion between coupling interneurones and the S‐cell passes current in both directions. 3. Selective destruction of the coupling interneurones by intracellular injection of a protease interrupts the disynaptic electrical connexion between touch and S‐cells. 4. The touch cell's geometry and membrane properties account for the failure of impulses that are generated in certain portions of the receptive field in the skin to propagate beyond the first branch‐points of the touch cell axon within the ganglion. Conduction block at branch‐points is used to examine physiologically the spatial distribution of contacts between the touch cell and the coupling interneurones. In addition, it is shown that under natural conditions branch‐point failure presynaptically reduces the effectiveness of the electrical synaptic connexions.