Multichannel Systems HiClamp Manual - Manual (Page 53)

Troubleshooting
47
6.3.1 Statistic
Activation of the statistic button displays the average and SEM for the points that can be fitted
by a single or dual Hill equation. Note that each curve can be fitted separately and the mean of
curve can later be computed and analyzed. Values corresponding to the original data points and
normalized values are stored in an excel compatible format by activation of the excel icon.
For the single Hill equation and a concentration activation curve the equation used for
the curve fitting is in the form:
Y=1 / 1+( EC
50
/ x)^n
H
where: y = the fraction of evoked current, EC
50
= concentration for 50 % activation,
nH = the apparent cooperativity, x = agonist concentration.
Dual concentration-activation curves are fit using the equation:
Y=a / 1+( EC
50H
/ x)^nHH +(1-a) / 1+( EC
50L
/ x)^nHL
where: y = the fraction of evoked current, EC
50H
= concentration for 50 % activation and
nHH = the apparent cooperativity of the high affinity component, a the fraction of high
affinity component, EC
50L
= concentration for 50 % activation and nHL = the apparent
cooperativity of the low affinity component , x = agonist concentration.
Concentration inhibition curves are fitted using comparable single or dual Hill equation with:
Y=1 / 1+( x/IC
50
)^n
H
where: y = the fraction of remaining current, IC
50
= concentration for 50 % inhibition,
nH= the apparent cooperativity, x = antagonist concentration.
Dual concentration-inhibition curves are fitted using the equation:
Y=a / 1+( x/IC
50H
)^nHH +(1-a) / 1+( x/IC
50L
)^nHL
where: y = the fraction of remaining current, IC
50H
= concentration for 50 % inhibition and
nHH = the apparent cooperativity of the high affinity component, a the fraction of high
affinity component, IC
50L
= concentration for 50 % inhibition and nHL = the apparent
cooperativity of the low affinity component , x = antagonist concentration.
6.3.2 Example of a curve fitting
Examples of a curve fitting for the concentration activation using SIMPLEX.
Curve fitting of the data presented above can be effectuated in different mode. A first mode
consists in determining the best fit for each of the curve. This is done by selecting any one of
the curve (click on the desired data point).