Intradermal injections of bradykinin or histamine cause a flare-like vasodilatation in monkey. Evidence from laser Doppler studies.

The spreading cutaneous vasodilatation (flare) that follows a cutaneous injury is readily visible in humans but cannot be visualized in monkey. To determine if monkeys exhibit this neurally mediated reaction, cutaneous blood flow changes after intradermal injections of bradykinin and of histamine were monitored in the hairy skin of pentobarbital anesthetized monkeys. Using a laser Doppler device, recordings of cutaneous blood flow were made at distances of 15 and 25 mm from the injection of 50 microliters of saline, bradykinin (10(-3) M) and histamine (10(-3) M). These sites were beyond the radius of the wheal caused by bradykinin (6.3 mm) or histamine (6.8 mm). At both recording sites, both drugs caused an increase in blood flow that was significantly larger than that caused by the injection of the same volume of saline. These results provide evidence that although a flare is not visible in monkey skin, a flare-like vasodilatation does occur over an area of at least 50 mm diameter.