Fig. 5.
Isoflurane did not abolish underlying chemosensitive mechanisms in 5-HT neurons in culture. A: summary of changes in membrane potential (Em) of cultured 5-HT neurons induced by acidic aCSF (Acid.), isoflurane (1% Iso), and acidic aCSF in isoflurane (Acid. + 1% Iso) (F = 56.12, P < 0.001, n = 13). B: recording from a 5-HT neuron in culture whose firing was abolished by isoflurane. Current injection was increased from 77.7 pA to 159.8 pA to reverse the hyperpolarization induced by isoflurane. The response to acidosis was then as large as control despite the continued presence of isoflurane. C: summary of the effect of acidosis while giving current injection to reverse the hyperpolarization induced by isoflurane. Shown are firing frequencies in aCSF (pH 7.4) and acidic aCSF (pH 7.15) under control conditions (Ctrl, n = 12), in isoflurane while giving extra depolarizing current (1% Iso + depol., n = 12), and during washout of isoflurane (Wash, n = 7). Chemosensitivity remained intact in isoflurane (F1,28 = 40.01, P < 0.0001), and there was no effect of isoflurane after an increase in current injection (F2,28 = 0.4537, P = 0.6399) or interaction between pH and isoflurane (F2,28 = 0.1227; P = 0.8850). All error bars represent SE. ***P < 0.001.