Nedocromil sodium and sodium cromoglycate inhibit plasma extravasation in the guinea-pig conjunctiva

Nedocromil sodium (NS) and sodium cromoglycate (CS) (both applied locally into the conjunctival sac) reduced in a dose dependent manner plasma extravasation induced by topical bradykinin and by topical substance P (SP), NS being approximately ten times more potent than CS. Plasma extravasation induced by SP was unaffected by the histamine H(1) receptor antagonist, pyrilamine, which completely blocked the plasma extravasation induced by histamine. NS and CS reduced the plasma extravasation caused by the mechanical stimulation of the conjunctiva, a response that was not affected by the tachykinin NK(1) antagonist CP-(99.994). NS or CS did not affect the contraction of strips of the guinea-pig trachea in vitro caused by SP in the presence of the tachykinin NK(2) receptor antagonist SR-(48968). NS, more potently than CS, reduces the plasma extravasation caused by various inflammatory stimuli in the guinea-pig conjunctiva, without inhibiting tachykinin NK(1) receptors, but probably by acting at the level of the venular endothelium. However, an inhibitory action of NS and CS on neural transmission of sensory nerves cannot be excluded.