Neurokinin-1 receptor immunoreactivity in hypotension sensitive sympathetic preganglionic neurons

Substance P activation of neurokinin-1 (NK1) receptors on spinal sympatheti c preganglionic neurons (SPN) influences blood pressure. We identified SPN likely to subserve the baroreceptor reflex and established if these neurons showed NK1 receptor-immunoreactivity. Nitroprusside (NP) infusion or infer ior vena cava (IVC) constriction activated similar numbers of SPN. Of these , about 40% were NK1 receptor-immunoreactive after NP infusion, but only ab out 20% were NK1 receptor-immunoreactive after IVC constriction. The distri bution of Fos/NK1 receptor SPN suggested that substance P may preferentiall y target sympathoadrenal SPN. (C) 2001 Elsevier Science BY All rights reser ved.