Kainate receptors mediate responses to kainate in >99% of acutely prepared DRG neurons tested in our study.A, A pharmacological profile of kainate responses in a P0 DRG neuron is illustrated. Kainate (KA)-induced whole-cell currents (bottom traces) were accompanied by Ca²⁺ increases (top traces). These were blocked by pretreatment with 3 μm SYM 2081 (KA + SYM). The neuron also displayed an inward current and Ca²⁺ increase with 1 μmcapsaicin (Cap). KA induced a small inward current and larger Ca²⁺ increase in the 0Na/10Ca bath solution (KA in 0NA/10Ca), providing additional evidence that the kainate receptors are Ca²⁺ permeable (n = 3). B, A similar series of experiments was done on a P3 DRG neuron. This neuron showsKA-induced whole-cell currents without a Ca²⁺ increase, indicating little Ca²⁺ permeability. KA + SYM blocked the response, and Cap induced an inward current.KA in 0Na/10Ca did not show any Ca²⁺increase, indicating no Ca²⁺ permeability of the receptors (n = 2). The horizontal bars above each current trace indicate the duration of drug application.