UII selectively excites bNOS-immunopositive mesopontine cholinergic neurons by evoking an inward current. A, Top, Membrane current from a PPT cell clamped near resting membrane potential (-60 mV) before and after bath superfusion of 300 nm UII. The slow inward current was observed in bNOS-immunopositive neurons. A1, The neuron from which the membrane current was obtained (Alexa 594; red). A2, The same field, with cholinergic neurons visualized by bNOS immunocytochemistry (FITC; green). A3, The two images, merged, revealing that the recorded neuron was immunoreactive for bNOS (yellow). The DIC image in A4 was obtained at the end of the recording and identifies the location of the recorded cell at the electrode tip. scp, Superior cerebellar peduncle; ll, lateral lemniscus; cll, commissural fibers of the ll. B, Bottom, Membrane current of a bNOS-immunonegative PPT neuron was unchanged after superfusion of UII. B1-B4 show that the recorded neuron was bNOS-immunonegative and also show its location (imaging is as described for A1-A4). Scale bars (for A and B): B1, 50 μm (for immunofluorescent images); B4, 200 μm (for DIC images). Breaks in current traces after UII application result from voltage jumps to assess conductance changes.
