Fig. 4: The modulation of muscarine on 5-HT neurons excitability.

A Muscarine increased the excitability of 5-HT neurons. A1 Muscarine induced membrane potential depolarization and spontaneous firing. A2 Muscarine decreased the rheobase. A3 Muscarine reduced the Rin. A4 Superimposed action potential recorded from a 5-HT neuron before (black) and after muscarine (red) showed that muscarine decreased AP height and AHP. A5-A9 Statistical results for the RMP, Rheobase, AP height AHP depth and Rin of 5-HT neurons recorded in control (black) and in the presence of 20 μM muscarine (red). B Muscarine decreased the excitability of 5-HT neurons. B1 Muscarine induced membrane potential hyperpolarization. B2 Muscarine increased the rheobase. B3 Muscarine reduced the Rin. B4 Superimposed action potential recorded from a 5-HT neuron before (black) and after muscarine (blue), muscarine decreased AP height and AHP. B5-B9 Statistical results listed for the RMP, Rheobase, AP height AHP depth and Rin of 5-HT neurons recorded in control (black) and in the presence of 20 μM muscarine (blue). C Muscarine did not significantly change the excitability of 5-HT neurons. C1-C2 Muscarine did not statistically change RMP (C1) and rheobase (C2). C3 Muscarine reduced the Rin. C4 Superimposed action potential recorded from a 5-HT neuron before (black) and after muscarine (grey), muscarine did not substantively change AP height and AHP. C5-C9 Statistical results summarized for the RMP, Rheobase, AP height AHP depth and Rin of 5-HT neurons recorded in control (black) and in the presence of 20 μM muscarine (grey). D Muscarine effects on 5-HT neuron RMP in the medulla. D1 Three-type effects induced by muscarine on the RMP of 5-HT neurons and their distribution. D2 Proportions of three type effects by muscarine on the RMP in PPR and MRN, respectively. Error bars represented SD; paired t-test performed; ∗: P < 0.05, ∗∗: P < 0.01, ∗∗∗: P < 0.001.