10. ELECTRIC ORGANS
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mediating homeostasis. It is also common in sensory and motor pathways
where it may increase spatial resolution. Yet many phenomena involve
recruitment of large numbers of cells in ways that appear to require
mutual reinforcement of neuronal activities, that is, positive feedback.
IV. CONCLUSIONS AND PROSPECTS
The study of electric organs and electrocytes has illuminated many
aspects of membrane physiology. Their primary usefulness is a result
of evolution which has exaggerated different membrane functions in
different electrocytes. For example, the concept of independent sites
that pass different ions or groups of ions becomes more reasonable
given that specific kinds of permeability can occur in isolation in different
regions of a single cell or in different cells. Examples are the isolated
occurrence of membrane generating postsynaptic potentials (in Astroscopus and torpedinids ) , of membrane exhibiting delayed rectification
(in rajids), and of the electrically excitable sodium system without
delayed rectification (in the electric eel), This macroscopic separation
suggests microscopic separation, which in many single membranes can
only be inferred from functional arguments or pharmacological data.
These specializations of different kinds of membrane cannot really
be said to have been responsible for major advances in electrophysiological knowledge. Yet as new morphological, biochemical, and biophysical techniques become available, electrocytes may provide the best
tissues for their evaluation.
Although one cannot determine electrophysiologically whether or
not sodium and potassium channels of ordinary spike-generating membrane are separate, one can begin to think about isolating them biochemically. Electric organs would appear to provide a good starting
material just as they are proving useful in the characterization of
cholinesterase and sodium-potassium ATPase. By selection of cell type,
one can select different kinds of membrane with relatively great degrees
of purity compared to most other tissues.
The neural systems controlling electric organs have provided a large
number of examples of electrically mediated transmission, which meets
the functional requirement for rapid communication between cells. This
mode of transmission also proves to be able to mediate many functions
often considered as restricted to chemically mediated transmission. The
correlation between morphologically close apposition and electrotonic
coupling was considerably strengthened by the work on electromotor
483
mediating homeostasis. It is also common in sensory and motor pathways
where it may increase spatial resolution. Yet many phenomena involve
recruitment of large numbers of cells in ways that appear to require
mutual reinforcement of neuronal activities, that is, positive feedback.
IV. CONCLUSIONS AND PROSPECTS
The study of electric organs and electrocytes has illuminated many
aspects of membrane physiology. Their primary usefulness is a result
of evolution which has exaggerated different membrane functions in
different electrocytes. For example, the concept of independent sites
that pass different ions or groups of ions becomes more reasonable
given that specific kinds of permeability can occur in isolation in different
regions of a single cell or in different cells. Examples are the isolated
occurrence of membrane generating postsynaptic potentials (in Astroscopus and torpedinids ) , of membrane exhibiting delayed rectification
(in rajids), and of the electrically excitable sodium system without
delayed rectification (in the electric eel), This macroscopic separation
suggests microscopic separation, which in many single membranes can
only be inferred from functional arguments or pharmacological data.
These specializations of different kinds of membrane cannot really
be said to have been responsible for major advances in electrophysiological knowledge. Yet as new morphological, biochemical, and biophysical techniques become available, electrocytes may provide the best
tissues for their evaluation.
Although one cannot determine electrophysiologically whether or
not sodium and potassium channels of ordinary spike-generating membrane are separate, one can begin to think about isolating them biochemically. Electric organs would appear to provide a good starting
material just as they are proving useful in the characterization of
cholinesterase and sodium-potassium ATPase. By selection of cell type,
one can select different kinds of membrane with relatively great degrees
of purity compared to most other tissues.
The neural systems controlling electric organs have provided a large
number of examples of electrically mediated transmission, which meets
the functional requirement for rapid communication between cells. This
mode of transmission also proves to be able to mediate many functions
often considered as restricted to chemically mediated transmission. The
correlation between morphologically close apposition and electrotonic
coupling was considerably strengthened by the work on electromotor