Figure 10. Serotonergic neurons respond to CO₂.

Neurons in cell cultures from the medullary raphe’ are chemosensitive to acidosis. (A) Example of the firing rate of an acidosis-stimulated neuron in response to respiratory acidosis and alkalosis. Lower trace is bath pH measured simultaneously at the inflow to the recording chamber. (B) Example of the firing rate of an acidosis-inhibited neuron in response to the same stimuli. (C) Acidosis-stimulated neurons respond to both respiratory acidosis and metabolic acidosis, indicating that a change in pHo (and/or intracellular pH), in the absence of changes in CO₂, is sufficient for a response to occur. (Reprinted from Respiration Physiology, 129, Richerson et al., Chemosensitivity of serotonergic neurons of the rostral ventral medulla. 175–189, 2001, (217) with permission from Elsevier.)