Effect of beta adrenergic stimulation and blockade on cutaneous reactivity to histamine

It has been previously demonstrated that iontophoresis of beta adrenergic agents will alter the size of immediate hypersensitivity skin tests. It was unclear whether this alteration was due to an effect on the dermal mast cell (inhibition of histamine release) or on the cutaneous vasculature (inhibition of capillary permeability). For this reason isoproterenol, propranolol, diphenhydramine as a positive control, and saline as a negative control were iontophoresed onto the forearm of 10 atopic and 10 nonatopic adult subjects. In order to bypass histamine release from mast cells the patients were then challenged directly with histamine by the "prick" technique. The size of the resultant wheals was noted. The data obtained allowed the following conclusions: (1) The atopic group responded to histamine with greater wheal size than the nonatopic group. (2) Iontophoresis of diphyenhydramine effectively reduced the magnitude of the histamine wheal in both groups. (3) Isoproterenol decreased the wheal size in both groups. (4) Propranolol increased the wheal size in only the nonatopic group. (5) The successful modulation of the histamine-induced wheal and flare indicated that these drugs, regardless of their effect on the dermal mast cell, exert a measurable effect on the target organ (vasculature).