Electrophysiological properties of the tongue epithelium of the toad Bufo marinus
Timothy K. Baker,
Karina Rios and
Stanley D. Hillyard*
Department of Biological Sciences, University of Nevada Las Vegas,
Las Vegas, NV 89154-4004, USA
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Fig. 1. A recording from a typical experiment in which NaCl and KCl Ringer were
exchanged sequentially as the mucosal and serosal bathing solutions. The
solution changes (mucosal/serosal) are indicated on the figure.
Isc, short-circuit current.
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Fig. 2. Power spectra obtained from experiments with (A) NaCl Ringer as the mucosal
and serosal bathing solutions, (B) NaCl Ringer as the serosal solution and KCl
Ringer as the mucosal solution and (C) NaCl Ringer as the mucosal solution and
KCl Ringer as the serosal solution. Note the presence of two Lorentzian
components in C. The spectra from A and B are from sequential treatments of
the same preparation as depicted in Fig.
1. Sf, spectral density. The arrows on the
spectra indicate the range of data points selected for the computer fit of the
spectra using equation 1.
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Fig. 3. The inhibition of short-circuit current (Isc) by the
addition of Ba2+ to the mucosal Ringer's solution. The x
axis scale reflects the sequence of treatments, which were applied at
approximately regular intervals. In these experiments, the mucosal and serosal
baths were NaCl Ringer. Isc values marked with an asterisk
are significantly inhibited relative to the control value. Removal of
Ba2+ restores Isc to its control value. The
changes in the power density of the Lorentzian plateau at low frequencies
(So) and the corner frequency (fc) are
not significant. Values are means ± S.E.M., N=6.
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Fig. 4. Direct linear plots for Ba2+ inhibition of short-circuit current
(Isc). (A) Experiments with NaCl as the mucosal and
serosal bathing solution; the mean control value of Isc
was -13.00 µA cm-2 (the y intercepts are the means for
six experiments). (B) Experiments with NaCl and KCl as the mucosal and serosal
solutions, respectively (N=4). The mean control
Isc for these experiments was -30.37 µA
cm-2. Note that the lines do not all intersect at a common point as
would be predicted if the Ba2+ inhibition were due to binding to a
single site with a single binding affinity. The broken lines indicate the
x intercept in A and B, which is the Ki value for
Ba2+ inhibition at lower concentrations. In B, the broken
horizontal line indicates the blocker-sensitive Isc (not
drawn in A).
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Fig. 5. The inhibition of short-circuit current (Isc) by 10 and
100 µmol l-1 quinine added to the mucosal Ringer. Note that
removal of quinine does not reverse the inhibition of Isc,
while the addition of 10 mmol l-1 Ba2+ does produce a
further inhibition that is reversible. In all experiments, NaCl Ringer was the
mucosal and serosal bathing solution. The values for the Lorentzian plateau at
low frequencies (So) decrease with Isc
as the quinine concentration is increased and remain low after quinine
wash-out and during Ba2+ treatment. So does
increase when Isc values return to more negative values
following the removal of Ba2+. Values marked with an asterisk
indicate that Isc and So are reduced
significantly relative to the control values. The value marked with a dagger
indicates that the value of Isc following treatment with
10 mmol l-1 Ba2+ is significantly different from the
quinine wash-out value. The corner frequencies (fc) do not
change significantly over the course of the mucosal solution changes. Values
are means ± S.E.M., N=6.
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© The Company of Biologists Ltd 2002
