NK1 receptor and the ventral medulla of the rat: bulbospinal and catecholaminergic neurons

Bulbospinal CI neurons are sympathoexcitatory and excited by substance P. H owever the substance P receptor (NKI receptor), has been reported to be abs ent from the somata of CI neurons. In this study, using double and triple l abelling immunofluorescence and retrograde tracing, we provide evidence tha t the NKI receptor is present on 5.3% of CI neurons, and that 4.7% of CI ne urons receive close oppositions from NK I receptor immunoreactive terminals , indicating a pre-synaptic and post-synaptic site for the action of substa nce P. These results provide support for the sympathoexcitatory actions of substance P on CI neurons. We also demonstrate the NKl receptor on bulbospi nal neurons of the ventral respiratory group, in a region overlapping the p re-Botzinger Complex. NeuroReport 12:3663-3667 (C) 2001 Lippincott Williams & Wilkins.