Fig. 1: Effects of D- and L-cis-diltiazem on rod and cone CNGC activity.

a–d Concentration-activation relationships for heterotetrameric cone (a, c) and rod (b, d) CNGCs, heterologously-expressed in Xenopus oocytes, in the presence of either D- or L-cis-diltiazem, measured at −35 mV. The respective curves represent fits of the experimental data points with the Hill equation (Eq. 1). Black symbols show the normalised cGMP-triggered current amplitudes in the absence of diltiazem. Light- and dark-blue symbols represent data obtained in the presence of D-cis-diltiazem, at 25 and 100 µM, respectively (a, b). Light- and dark-red symbols represent data obtained in the presence of L-cis-diltiazem at 25 and 100 µM, respectively (c, d). e, f D- and L-cis-diltiazem block (%, ±SEM) of CNGCs in the presence of 3 mM (e) and 100 µM cGMP (f), respectively. The amount of diltiazem block was calculated using Eq. 2 (see “Materials and methods”). The respective symbols represent single measurements (see also Tables S1 and S2).