Plateau basal firing rate response following substance P.

<p>Representative samples of plateau basal firing rate responses to prolonged substance P (SP) exposure of SC neurons from both a control (A) and a CHx rat (B). Black bar represents SP exposure. (A) Sample plateau response to SP of an SC neuron from a control rat. Notice that basal firing rate slowly rose in response to SP and plateaued around 4–5 Hz. Before we exposed the neuron to hypercapnia, we first hyperpolarized the neuron by injecting negative DC current to return firing rate back to initial values. (B) Sample plateau response to SP of an SC neuron from a CHx rat. Notice that basal firing rate plateaued in response to SP to approximately 4–5 Hz. Before we exposed the neuron to hypercapnia, we first hyperpolarized the neuron by injecting negative DC current to return firing rate back to initial values. Note, that in both types of rats, firing rate plateaued at ∼4–5 Hz.