10. ELECTRIC ORGANS
459
ing superior in respect to temporal resolution to what has been possible
with skeletal muscle fibers (Adrian et al., 1970). One important measurement that has not been obtainable from muscle fibers is the high speed
of onset and reversal of anomalous rectification (Bennett and Grundfest,
1966; Nakamura et al., 1965; Morlock et al., 1969). The primary factor
is that the time constant of the excitable membrane is much lower in
electrocytes and there is less interference from capacitative currents.
Isolated eel electrocytes can be of value in flux measurements
( Higman et al., 1964), although the spatial uniformity of concentration
as well as potential becomes important and the conductances are SO large
that intracellular concentrations can change rapidly ( Karlin, 1967). Still
the large amounts of synaptic as well as spike generating membrane and
the possibility of approximately controlling transmembrane potential
during drug application and flux measurements are features not readily
available in muscle.
Electrocytes do not appear as good as muscle for electrophysiological
study of many aspects of synaptic transmission. The presynaptic fibers
are no larger than those in muscle and usually do not end in a localized
but accessible region. The low input resistance of the cells makes them
less useful for study of miniature PSPs and actions of restricted synaptic
areas. The low input resistance and wide distribution of synaptic membrane also impede studies using iontophoretic application of drugs, which
remains the best method for study of kinetics of drug action. Nonetheless,
through experimental simplicity, electrocytes have been and should
continue to be useful in studies involving relatively gross application of
drugs during current application and recording of PSPs (e.g., Karlin,
1969).
The kinds of problems where electrocytes are likely to be particularly
useful are in the area of biochemistry. The organs are a rich source of
acetylcholinesterase ( Leuzinger and Baker, 1967), and much of the work
characterizing the enzyme has been done on material of this origin.
Moreover, the eel electric organ is probably the richest known source of
the sodium-potassium transport ATPase and has been used in studying
this enzyme ( Albers, 1967; Post et al., 1969). Eel electric organ does not
have a particularly high concentration of mitochondria compared to a
number of muscles, which suggests that its mean metabolic rate is not
particularly high. Nevertheless, the only work it does is generation of
electricity. Thus, it is reasonable that its sodium-potassium ATPase levels
should be very high. From the much greater concentration of mitochondria in electrocytes of repetitively active weakly electric fish
(Schwartz et al., 1971) one would expect there to be considerably higher
levels of the transport ATPase. Of course, the weight of organ available
459
ing superior in respect to temporal resolution to what has been possible
with skeletal muscle fibers (Adrian et al., 1970). One important measurement that has not been obtainable from muscle fibers is the high speed
of onset and reversal of anomalous rectification (Bennett and Grundfest,
1966; Nakamura et al., 1965; Morlock et al., 1969). The primary factor
is that the time constant of the excitable membrane is much lower in
electrocytes and there is less interference from capacitative currents.
Isolated eel electrocytes can be of value in flux measurements
( Higman et al., 1964), although the spatial uniformity of concentration
as well as potential becomes important and the conductances are SO large
that intracellular concentrations can change rapidly ( Karlin, 1967). Still
the large amounts of synaptic as well as spike generating membrane and
the possibility of approximately controlling transmembrane potential
during drug application and flux measurements are features not readily
available in muscle.
Electrocytes do not appear as good as muscle for electrophysiological
study of many aspects of synaptic transmission. The presynaptic fibers
are no larger than those in muscle and usually do not end in a localized
but accessible region. The low input resistance of the cells makes them
less useful for study of miniature PSPs and actions of restricted synaptic
areas. The low input resistance and wide distribution of synaptic membrane also impede studies using iontophoretic application of drugs, which
remains the best method for study of kinetics of drug action. Nonetheless,
through experimental simplicity, electrocytes have been and should
continue to be useful in studies involving relatively gross application of
drugs during current application and recording of PSPs (e.g., Karlin,
1969).
The kinds of problems where electrocytes are likely to be particularly
useful are in the area of biochemistry. The organs are a rich source of
acetylcholinesterase ( Leuzinger and Baker, 1967), and much of the work
characterizing the enzyme has been done on material of this origin.
Moreover, the eel electric organ is probably the richest known source of
the sodium-potassium transport ATPase and has been used in studying
this enzyme ( Albers, 1967; Post et al., 1969). Eel electric organ does not
have a particularly high concentration of mitochondria compared to a
number of muscles, which suggests that its mean metabolic rate is not
particularly high. Nevertheless, the only work it does is generation of
electricity. Thus, it is reasonable that its sodium-potassium ATPase levels
should be very high. From the much greater concentration of mitochondria in electrocytes of repetitively active weakly electric fish
(Schwartz et al., 1971) one would expect there to be considerably higher
levels of the transport ATPase. Of course, the weight of organ available