Permeability increase in rat submandibular gland by glandular substance P

When the chorda tympani was stimulated at 20 Hz, infused horseradish peroxidase (HRP) entered the saliva through the tight junctions in the rat submandibular gland. This response was not inhibited by atropine but was reduced by a substance P(SP)-antagonist. The increase in junctional permeability for HRP never occurred in the gland that was stimulated at 5 Hz or in the SP-depleted gland. Our data suggest that the effect of parasympathetic stimulation on the increase in junctional permeability for macromolecules was due to the release of SP in the gland.