Chemosensitivity response of SC neurons to substance P.

<p>Percentages of SC neurons that were activated (A and B) or inhibited (E and F) by hypercapnic acidosis in the absence (SNB) or presence of substance P (SP) from control rats (N = 10 and N = 12 in the absence and presence of SP for CO₂-activated SC neurons, A; N = 3 in the absence and presence of SP for CO₂-inhibited SC neurons, E) and from CHx rats (N = 13 and N = 10 in the absence and presence of SP for CO₂-activated SC neurons, B; N = 6 and N = 3 in the absence and presence of SP for CO₂-inhibited SC neurons, F). Chemosensitivity indices (CI) of SC neurons (same neurons as in A, B, E and F) that were CO₂-activated (C and D) or CO₂-inhibited (G and H) by hypercapnic acidosis in the absence or presence of SP from control rats (C and G) and CHx rats (D and H). In all cases, white bars represent synaptic blockade (SNB) solution and black bars represent SP. (A-D) The percentage and CI of SC neurons that were activated by hypercapnic acidosis in the absence and presence of SP from control and CHx rats, where the percentage and CI were not affected by SP. (E-H) The percentage and CI of SC neurons from control and CHx rats that were inhibited by hypercapnic acidosis in the absence and presence of SP, where the percentage and CI were not affected by SP. The height of each bar represents either the percentage CO₂-activated (A and B) or CO₂-inhibited (E and F) or the mean CI for that group (C, D, G and H) ± S.E.M.