Role of substance P in the vascular response of nasal mucosa in nasal allergy.

The effects of topically administered substance P (SP) on nasal blood flow and nasal airway resistance (NAR) were evaluated in 11 subjects with perennial nasal allergy. The change in NAR induced by SP was compared with those induced by nasal challenge with histamine, leukotriene D4 (LTD4), and antigen. In doses > or = 16 nmol, SP caused a significant increase of nasal blood flow within 5 minutes that lasted for less than 20 minutes. In doses > or = 16 nmol, SP caused a dose-dependent, short-lasting, significant increase in NAR. The magnitude of the increase in NAR was LTD4 > SP > histamine when compared on a molar basis. Our results may suggest that SP released from C fiber terminals is partially involved in an early nasal vascular response after antigen challenge by acting on adjacent vascular smooth muscle to cause a transient vasodilatation of both resistance and capacitance vessels only while sensory stimulation persists in subjects with nasal allergy.