THE CAPSAICIN-INDUCED INFLAMMATORY REACTION IN THE CAT EYE - ANTAGONISM BY RUTHENIUM RED

The neurogenic ocular inflammatory response in the cat was investigated by means of intracameral injections of capsaicin. At a dose of 200 μg intracamerally the eye responded with a breakdown of the blood-aqueous barrier (BAB) and a transient ocular hypertension. A response of the same magnitude was observed when a dose of 1 μg capsaicin was given. Most of the response to this lower dose was prevented by ruthenium red, an inorganic dye thought specifically to antagonize the effects of capsaicin on sensory nerve endings. Following injection of 200 μg capsaicin there was a transient increase in pupil size, but this response was not seen after 1 μg. Repeated injections of 200 μg capsaicin when the effects of the first dose had vanished resulted in tachyphylaxis of the mydriatic response. A dose of 200 μg of capsaicin had no effect on resistance in the outflow routes for aqueous humour. © 1991.