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. Author manuscript; available in PMC: 2015 Feb 14.
Published in final edited form as: Neuroscience. 2013 Dec 10;259:203–213. doi: 10.1016/j.neuroscience.2013.11.060

Figure 2. CO2-stimulated putative 5-HT and non-5-HT cells are distinct, and putative non-5-HT cells are more robustly stimulated by CO2 than are putative 5-HT cells.

Figure 2

(A–C) Recordings from single CO2-stimulated raphé neurons show spontaneous firing during exposure to 5% arterial CO2 (left column), a >20% increase in firing frequency with exposure to 9% CO2 (center column), and recovery with return to 5% CO2 conditions (right column). (A) A 5-HT neuron increased firing by 38% during hypercapnia. (B) A non-5-HT neuron had a 56% hypercapnic response, and another non-5-HT neuron (C) had a 101% hypercapnic response. (D) In CO2-stimulated cells, hypercapnia caused a mean 49% increase in firing rate of putative 5-HT cells (filled circles, †), and a mean 110% increase in firing rate of putative non-5-HT cells (open circles, ϕ). Normocapnic recovery returned firing frequencies to baseline levels. Firing frequencies differed between CO2-stimulated putative 5-HT and non-5-HT neuron groups during all gas conditions (∗, ∗∗, ∗ ∗ ∗). (E) Hypercapnic firing frequencies normalized to respective baseline firing frequencies confirm differences in hypercapnic responses between the CO2-stimulated putative 5-HT and non-5-HT neuron groups (∗). Symbols denote p <0.05 between means (e.g. means labeled “*” differ from each other, means labeled “†” differ from each other, etc.).