Effects of BP 2-94, a selective H3-receptor agonist, on blood flow and vascular permeability of the rat mandibular incisor pulp

Pulpal blood-flow changes were monitored by laser Doppler flowmetry after electrical stimulation of the mandibular incisor. Stimuli of 10 s (50 μA, 2 ms, 20 Hz) were applied to the incisors of untreated animals and longer stimulations (5 min) were applied in animals treated with the α-blocker phenoxybenzamine. Changes in vascular permeability in the dental pulp were measured by Evans blue extravasation following resection of the superior cervical ganglion. In these groups, a selective agonist of H3 receptors, BP2-94 (1.5 and 15 mg/kg), and an H3-antagonist ciproxifan (1 mg/kg) were administered. The effects of these drugs were compared with those obtained from animals treated only with the vehicle (methylcellulose 1%). Basal pulpal blood-flow was not affected significantly by BP2-94 or ciproxifan. The vasoconstriction induced in the group of intact rats by electrical stimulation of 10 s is decreased in amplitude and duration at the higher dose of BP2-94 by 58 and 40%, respectively (P<0.05, n=5). In the sympathectomized animals, plasma extravasation was significantly increased at 15 mg/kg BP2-94 (+100%, P<0.01, n=5). These results suggest that H3 receptors may participate in the regulation of changes in vessel contraction and permeability provoked by electrical stimulation of the dental pulp. However, the non-selective effects of the H3 agonists reacting on adrenergic sites and H1 receptors could explain a part of the results.