f = a+ g1/(1+exp((x-V1/21)/k1)) +
g2/(1+exp(-(x-V1/22)/k2))
where x is the pre-pulse potential, V1/2is the mid-point potential and k is the corresponding slope
factor for single Boltzmann functions. Double Boltzmann fits were used
to describe the shape of the curve, not to imply the existence of
separate channel populations. Numbers 1 and 2 simply
indicate first and second mid-points; a along with g are
fitting parameters.
Activation curves were obtained from the I-V curves by dividing the peak
current at each depolarizing step by the driving force according to the
equation: G=
I/(Vmem- Erev) ,
where I is the peak current, Vmem is the
membrane potential and Erev is the reversal
potential. The conductance (G) was normalized against the maximum
conductance (Gmax). For total and the different subtypes
of
Ca2+For
Na+max). Activation and SSI curves
were fitted with the Boltzmann equation.