Figure 1. Sumatriptan inhibits high threshold voltage gated Ca²⁺ currents (I_Ca) in dural afferents.

A. Example of sumatriptan mediated inhibition of I_Ca. B. Bath application of increasing concentrations of sumatriptan from 0.001 to 10μM suppressed I_Ca amplitude recorded with a single pulse to 10mV in 7 of 7 dural afferents studied. C. The IC₅₀ for sumatriptan was determined with percent inhibition plotted against sumatriptan concentration. D. To examine the voltage dependence of inhibition, currents were elicited with a test pulse to +10mV following pre-pulses to −60 and +80mV before (Baseline) and after sumatriptan (10 μM Suma) application (n=5). The ratio of the current amplitude following a prepulse to +80 divided by the current amplitude following a prepulse to −60 was determined before and after sumatriptan application. Following sumatriptan application, there was no significant difference in the current ratio. E. Instantaneous I–V data were plotted from tail currents. Sumatriptan decreased the amplitude of the tail currents but did not produce a shift in their voltage dependence of activation.