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Fig. 6. Voltage sensitivity of nematocytes in the absence of chemical
sensitization. (A) Voltage responses of a nematocyte from
Stauridiosarsia to depolarizing current steps, increased in
increments of 0.25 nA, starting from –100 mV. At depolarizations above
–10 mV a regenerative action potential is elicited. (B) Typical action
potential at a threshold of –8 mV, induced by current injection. (C)
Voltage responses of a nematocyte from Dipurena to depolarizing
current steps, increased in increments of 0.5 nA, starting from resting
voltage. At about –40 mV a regenerative, persistent depolarization is
triggered, while an action potential occurs at a threshold close to 0 mV. (D)
Membrane currents from a Stauridiosarsia nematocyte recorded in
discontinuous voltage-clamp mode in response to voltage steps in increments of
10 mV, starting from –70 mV (data are shown with linear leak currents
subtracted). (E) Membrane currents from D as a function of membrane potential:
steady-state currents (open symbols) are compared to transient values (filled
symbols). Transient inward currents activate at about –10 mV, matching
the action potentials threshold.
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