Fig. 4.
Isoflurane inhibited firing of 5-HT neurons in vitro and abolished their response to CO2. A: confocal microscopy image of a cultured medullary ePet-EYFP neuron. green, EYFP; blue, DAPI nuclear stain. Scale bar, 25 μm. B: firing frequency and pH of a recording from a cultured medullary 5-HT neuron. Firing increased during acidosis. Isoflurane (1%) eliminated firing in aCSF, and firing did not return in acidosis. C: summary of current-clamp recordings. 5-HT neurons had a robust increase in firing frequency in response to acidosis (Ctrl, n = 15). Isoflurane eliminated firing and prevented any change in response to acidosis (1% Iso, n = 15). These effects were reversible (Wash, n = 12). A 2-way repeated-measures ANOVA revealed a significant effect of pH (F1,39 = 41.77, P < 0.0001) and isoflurane (F2,39 = 12.25, P < 0.0001). Furthermore, there was an interaction between pH and isoflurane (F2,39 = 8.568, P = 0.0008). Error bars represent SE. ***P < 0.001.