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Figure S1 Iberiotoxin-induced depolarizations may cause a reduction in firing. (A,B) Representative trace and corresponding frequency histogram illustrating that in some neurons iberiotoxin can produce strong depolarization that initially causes an increase in spontaneous firing that then reverses to a low firing rate, presumably due to sodium channel inactivation.

Figure S2 Tachyphylactic effect of BKCa channel blockers. (A) Facilitation of microiontophoretically applied l-glutamate-evoked action potential firing of a single trigeminovascular second-order sensory neuron by iberiotoxin (IbTx). l-glutamate was ejected in pulses (−20 nA for 9 s of every 15 s) as indicated by the bars. When l-glutamate-evoked firing had reached a steady state over five epochs, iberiotoxin was microiontophoretically co-ejected (100 nA) over a period of about six l-glutamate pulses, as indicated by the solid horizontal bar. Signal obtained from amplitude discriminated spikes passing a threshold above noise level was pooled in 1-s bins displayed across the horizontal axis to give a firing rate in Hz indicated on the vertical axis. Neurons showed this distinct tachyphylaxis effect particularly after the application of toxins at higher currents (100–400 nA) effecting an initially large increase in firing rate. Cells were considered to respond tachyphylactically if the Pearson correlation across the first five epochs of l-glutamate application during microiontophoresis of the BKCa channel blocker was < −0.5. Error bars indicate the standard error of the means. (B) Tachyphylaxis to iberiotoxin was observed in 32% (6/19) trigeminovascular second-order sensory neurons in the trigeminal nucleus caudalis linked to electrical superior sagittal sinus stimulation, where facilitation by the toxin lost significance compared with baseline firing (P < 0.05, two-tailed one-sample t test) after two l-glutamate epochs. (C) Tachyphylaxis to slotoxin was observed in 38% (11/29) of cells and facilitation by slotoxin lost significance compared with baseline after just one epoch of l-glutamate application.

Figure S3 CGS19755 and 6-cyano-7-nitroquinoxaline-2,3-dione disodium (CNQX) have no effect on spontaneous action potentials in individual trigeminal nucleus caudalis neurons in a slice preparation. (A,B) Representative trace and corresponding frequency histogram illustrating that CGS19755 and CNQX have no effect on the spontaneous action potentials measured by extracellular recordings in the current clamp mode (n = 3 neurons). Bin size is 3 s.

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Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.