Fig. 8

Tachyphylaxis of responses to repetitive diode laser heat stimulation in vivo as well as in vitro and partial block by TRPV1 antagonist capsazepine. a Original trace of responses of a single transfected HEK cell to repetitive diode laser heat stimuli (135 mW, 5 ms). b Original trace of responses of a single DRG neuron to repetitive diode laser heat stimuli (135 mW, 5 ms). c Tachyphylaxis of diode laser heat responses in HEK cells (filled bars) and DRG neurons (open bars) challenged three times with 135 mW, 5 ms laser stimuli (ISI 180 s). Changes in fluorescence ratio normalized to first stimulus. d Tachyphylaxis of diode laser induced heat pain on the human hand (dark grey) and foot (light grey) when stimulating the same spot repetitively (100 mW, 200 ms; ISI 180 s; n = 10). e Calcium transients of representative single transfected HEK cells challenged with repeated laser stimulation (135 mW, 5 ms) before (first stimulus) and during (second stimulus) incubation with 10 µM CPZ (black trace) or with vehicle (dashed grey). Values are given in 340/380 nm fluorescence ratio. f The competitive TRPV1 antagonist capsazepine (CPZ) significantly reduced laser heat responses compared to vehicle application (by 48.6%; ***p < 0.001, unpaired t-test)