A PARTIAL INVOLVEMENT OF HISTAMINE IN ULTRASONICALLY NEBULIZED DISTILLED WATER-INDUCED BRONCHOCONSTRICTION IN GUINEA-PIGS

1 Inhalation of ultrasonically nebulized distilled water (UNDW) can in duce bronchoconstriction only in asthmatics, but mechanisms of the res ponse are not well known. We recently reported a guinea-pig model of U NDW-induced bronchoconstriction (UNDW-IB) in which UNDW induces bronch oconstriction when UNDW is inhaled 20 min after a challenge with aeros olized ovalbumin (OA) in passively sensitized, anaesthetized and artif icially ventilated guinea-pigs. 2 To elucidate the role of histamine i n the UNDW-IB, we examined the effects of antihistamines, diphenhydram ine hydrochloride (DH) and chlorpheniramine maleate (CP), and measured histamine content in bronchoalveolar lavage fluid (BALF) in the anima l model. 3 DH in doses of 0.1, 1.0 and 10 mg kg(-1) and CP in doses of 0.01, 0.1 and 1.0 mg kg(-1) administered intravenously 15 min after t he OA challenge partially reduced the UNDW-IB at 1 and 2 min after the UNDW inhalation in a dose-dependent manner. Histamine content in BALF recovered 10 min after the UNDW inhalation following the OA provocati on was significantly increased compared with that after saline inhalat ion and before the UNDW inhalation following the OA challenge. 4 Intra venous atropine in a dose of 0.5 mg kg(-1) or inhaled disodium cromogl ycate in concentrations of 1 and 10 mg ml(-1) did not alter the UNDW-I B. 5 These results suggest that histamine is involved in part in the U NDW-IB in our animal model.