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

Abstract

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 H₁ 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 NK₁ 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 NK₂ 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 NK₁ 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.

Key Words:

• Nedocromil sodium
• sustance P
• bradykinin
• plasma extravasation
• conjunctiva