The histamine H4 receptor antagonist JNJ7777120 induces increases in the histamine content of the rat conjunctiva.

Although the H(4) receptor localisation in the eye is unresolved, this study aimed to investigate the effects of the H(4) receptor antagonist JNJ7777120 in a model of experimental conjunctivitis. JNJ7777120, at 0.005-1 mmol/l, was instilled into the lower conjunctival fornix of normal and compound 48/80 (C48/80)-challenged eyes of male Wistar rats, in the absence or presence of 40 mg/ml disodium cromoglycate (DSCG). Conjunctival histamine content was quantified 20 min post-challenge. Statistical analyses were performed by ANOVA. JNJ7777120 increased dose-dependently (r = 0.784, p < 0.001) the conjunctival histamine content. In the C48/80-challenged eye no effect of the antagonist was observed. Co-administration of JNJ7777120 with DSCG resulted in a biphasic action of JNJ7777120, implying a competitive action of the two agents. These data suggest a functionality of the H(4) receptor in the rat eye and address questions on the localization and the role of the receptor in ocular inflammation.