Characterization of a chloroquine-induced canine model of pruritus and skin inflammation

Background Chloroquine (CQ) is a prototypical systemic and intradermal pruritogen for histamine-independent (nonhistaminergic) itch in mice and humans. The predictive validity of this model is poorly documented in dogs. Hypothesis/Objective To determine pruritogenic and inflammatory effects of systemic and i.d. CQ injections in healthy dogs. Animals Ten healthy purpose-bred laboratory beagles. Methods and materials All dogs were randomized to receive i.d. (200 and 400 mu g/site), intravenous (2 mg/kg) and subcutaneous (3 mg/kg) CQ injections. Dogs were video-recorded for 30 min after i.d. injections and for 300 min after i.v. and s.c. injections. Buffered saline injections served as controls for each route. Global wheal scores were evaluated at 30 min post-i.d. injection by a blinded investigator. Results All dogs showed wheal and erythema at the CQ i.d. injection sites; global wheal scores of each CQ concentration were significantly increased compared to placebo (P <= 0.05). Blinded evaluation revealed no significant increase in generalized pruritic behaviour (pruritic seconds) after i.v. or s.c. administration of CQ. Intradermal injections induced mild localized acute pruritic behaviours at the site of injections at 200 mu g (P = 0.06) and 400 mu g (P = 0.27) CQ in dogs. Conclusion and clinical significance To the best of the authors' knowledge, this is the first report which shows that i.d. CQ injections may induce acute inflammation in healthy dogs. By contrast to the systemic CQ-induced pruritus reported previously in healthy mice and dogs, no significant pruritic behaviours were observed after CQ injection, regardless of the route of administration.