Figure 3.

CO₂ induced dose dependent CBF in stressed and unstressed animals. (A) Baseline CBF before the inhalation of CO₂. The left image is from an unstressed animal and the right is from a stressed animal. The colorbar represents the intensity of signal in a.u., which is directly proportional to regional cerebral blood volume (rCBV). (B) Dose dependent response to CO₂ inhalation. Each image represents the activation (increase in CBF normalized to the baseline) due to the inhalation of indicated percentage of CO₂. (i) Represents images from an unstressed animal. (ii) Represents images from a stressed animal. (C–E) Quantification of response to CO₂ inhalation in unstressed (N = 6) and stressed (N = 6) animals. (D) Normalized activation intensity (which is directly proportional to increase in cerebral blood flow normalized to baseline cerebral blood flow) in response to CO₂ inhalation. There is a significant effect of stress (p = 0.0261) and CO2 inhalation (p < 0.0001). The response of unstressed and stressed rats is significantly different for all the concentrations CO₂. (C) Activation area in response to CO₂ inhalation. There is a significant effect of stress (p = 0.0404) and CO₂ inhalation (p < 0.0001). The response of unstressed and stressed rats is significantly different for 10 % and 15% concentrations of CO₂. (E) Activation area normalized to the total slice area in response to CO₂ inhalation. There is a significant effect of stress (p = 0.0264) and CO₂ inhalation (p < 0.0001). The response of unstressed and stressed rats is significantly different for all the concentrations of CO₂.