Phenotypic transformation of sensory neuron by K+ channel blockade. A. Blocking effect of 100 μ M 4-AP on a slowly-inactivating K+ current that is responsible for preventing the response to cooling in cold insensitive trigeminal ganglion neurons. B. Simultaneous recording of [Ca2+]i and bath temperature in two trigeminal sensory neurons. The application of 100 μ M 4-AP unmasked a [Ca2+]i response in n2 during the second cooling step, transforming a cold-insensitive neuron into a cold-sensitive one. Adapted from Viana et al., 2002.