Parameters affecting excitability and an overexpression of Kcnc1 and
Kcnc2 in LR CA3 neurons. A.CA3 excitability (encoded in the radius of the dot,
see Methods) as a function of the amplitude
of the fast potassium currents (y-axis) and the kinetics or decay time constant
of the fast potassium current (x-axis). The larger dots are generally observed
in the neurons with fast kinetics or fast decay time of the fast potassium
currents. B. DG excitability (encoded in the radius of the dot, see Methods) as a function of the amplitude of
the fast potassium currents (y-axis) and the kinetics or decay time constant of
the fast potassium current (x-axis). The larger dots are observed in the neurons
with fast kinetics or fast decay time and higher amplitudes of the fast
potassium currents. C-E. The excitability in all the groups correlates with
sodium currents (at −20 mV). This correlation is much stronger in NR
neurons compared to control and LR neurons. F-H. A significant correlation is
observed between excitability and the amplitude of the fast potassium currents
at 0 mV in LR and NR neurons. The excitability in control neurons does not
correlate with the amplitude of the fast potassium currents at 0 mV. I. Blocking
of different potassium channels reduced excitability of CA3 BD neurons but
increased excitability of CA3 control neurons; Dendrotoxin (DTX) at 200 nM
significantly increased excitability of control neurons. 1 mM Tetraethylammonium
(TEA) most drastically reduced hyperexcitability of CA3 LR neurons, but 0.3 mM
of 4-aminopyridine (4-AP) and DTX also significantly reduced their
hyperexcitability. 4-AP reduced excitability of CA3 NR neurons. A total number
of 53 control, 28 control TEA, 27 control 4-AP, 28 control DTX, 47 LR, 39 LR
TEA, 18 LR 4-AP, 29 LR DTX, 104 NR, 28 NR TEA, 28 NR 4-AP and 28 NR DTX neurons
were recorded. J. qPCR results (fold change) of Kcnc1 showed that CA3 LR neurons
have elevated levels compared to control neurons. K. Fold change values of Kcnc2
showed a decreased expression in NR neurons and an increased expression in LR
neurons compared to CA3 control neurons. Asterisks represent statistical
significance by the following code: * p value<0.05, **p
value<0.01, ***p<0.001, ****p<0.0001. Error bars represent
standard error.