Topiramate is likely to act outside of the trigeminocervical complex

Background To facilitate understanding the locus and mechanism of action of antimigraine preventives, we examined the effect of topiramate on trigeminocervical activation in the cat. Methods Cats were anesthetized and physiologically monitored. Electrical stimulation of the superior sagittal sinus activated nociceptive trigeminovascular afferents. Extracellular recordings were made from neurons in the trigeminocervical complex. Results Microiontophoretically delivered topiramate, applied locally at the second order synapse of the trigeminovascular system in the trigeminocervical complex, produced significant inhibition of L-glutamate-evoked firing of neurons only at the highest microiontophoretic currents (27 ± 7% at −160 nA; p