Sensitivity of the rat gustatory system to the rate of stimulus onset.

Responses of the rat chorda tympani nerve were obtained to stimulation of the tongue with both linearly rising anodal current of varying intensity and rate of rise and NaCl presented at different concentrations and rates of flow. The amplitude of the transient portion of the integrated chorda tympani response was a power function of the rate of current rise. The duration of the transient response paralleled the rising phase of the current and the neural response fell to a tonic level proportional to current intensity when the rising current reached its plateau. Anodal currents of different final intensities but presented at the same rate of rise produced transient responses of the same amplitude. Responses of single chorda tympani fibers exhibited the same phasic and tonic components that were characteristic of the whole nerve. When NaCl was presented to the tongue at different rates of flow, the chorda tympani response reflected a sensitivity to stimulus onset rate paralleling that shown to linearly rising current.