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. 2016 Sep 28;36(39):10097–10115. doi: 10.1523/JNEUROSCI.0635-16.2016

Figure 4.

Figure 4.

The oeAHP current (IoeAHP) reverses near the potassium equilibrium potential (EK) and has a biphasic decay mediated by a medium duration SK current and a slower apamin-insensitive current. A, Continuous recording of membrane current in voltage-clamp mode (holding potential −65 mV) before and during application of orexin-A (Orx A, 300 nm). Intermittent 5 pulse protocols (delivered ∼30 s intervals) evoked AHP currents before (left, red dashed box) and after Orx A (right, blue dashed box). B, Top traces, Leak-corrected currents from A before (red) and after (blue) Orx A (3 traces averaged). Bottom trace (purple), IoeAHP, computed as the difference between the top traces. C, Membrane current in orexin (magenta) is superimposed on the membrane current evoked by the 5 pulse protocol (blue) in orexin. Brief (20 ms) voltage pulses (−115 mV to −55 mV in 10 mV increments, bottom black trace, inset) were delivered during both traces at a time corresponding to the peak of the oeAHP (bar). The current at the end of each brief step (top traces, inset) was used to estimate the instantaneous I–V relation. D, Resulting instantaneous current (mean ± SEM, Im)–voltage (Vm) relations for traces without the 5 pulse protocol (− prepulses, open squares, magenta) and traces with the 5 pulse protocol (+ prepulses, filled squares, blue) cross near the calculated potassium reversal potential (EK; n = 7). E, Apamin (100, 300 nm) reduced the amplitude (mean ± SEM) of IoeAHP (n = 23). *p < 0.05. F, The average IoeAHP (purple) under control conditions (n = 7; top) had a biphasic decay that was well fit with the sum of a medium and slow-decaying exponential (superimposed white trace). The average IoeAHP in apamin (n = 7; second trace) decayed with a single slow exponential (superimposed white trace). The average orexin-enhanced SK current (IoeSK, n = 5; third trace) was well fit with a medium-decaying single exponential (superimposed white trace). The average IoeAHP in UCL2077 (n = 4; fourth trace) also had a biphasic decay that was well fit with the sum of a medium and slow-decaying exponential (superimposed white trace).