Figure 3.

The excitatory effect of orexin is caused by activation of postsynaptic OX₂ receptors. A, Orexin-A (200 nm) reversibly depolarized Type-C neurons; whole-cell current-clamp recording in the presence of tetrodotoxin (1 μm). The membrane potential was set to -60 mV before orexin application by current injection to ensure the same initial conditions for all neurons. B, Concentration—response relations for membrane potential responses (recorded as in A) to orexin-A (n = 3–5) and orexin-B (n = 3–5). The lines were fit to the Hill equation with EC₅₀ of 19 and 21 nm, Hill coefficients of 1.8 and 1.1, and maximal amplitudes of 17.2 and 17 mV, respectively.