Local injection of SP-SAP selectively ablates preBötC NK1R neurons. Inset, transverse section of adult rat brainstem showing relative location of preBötC (circle) ventrolateral to scNA. Rectangle (excluding circle) indicates area outside preBötC analyzed for neuron counts (see text). Comparison of NK1R (a), choline acetyltransferase (ChAT) (b) and tyrosine hydroxylase (TH) (c) immunohistochemistry in unilaterally injected rat. scNA, semicompact division of nucleus ambiguus; IO, inferior olive; 5SP, trigeminal nucleus; XII, hypoglossal nucleus. Scale bars, 200 μm.