The present study was undertaken in vitro to examine the effect of histamine on the nasal vascular beds of normal and chemical sympathectomized dog and to determine the nature of histamine receptors at the adrenergic nerve terminal and vascular smooth muscle cells. Histamine, maximum concentration 10-2M, and epinephrine, maximum concentration 10-5M, increased contractile responses in a dose dependent manner. This contractile response of histamine was inhibited with each one of pyrilamine (10-4M), and cimetidine (10-4M) and the combined use of pyrilamine and cimetidine, and phentolamine (2.6×10-4M). After chemical sympathectomy, such response was also inhibited with pyrilamine (4×10-4M) and cimetidine (4×10-4M). In other observation of nasal mucosa treated with histamine (10-2M) and after chemical sympathectomy, the fluorescences were apparently reduced as compared with those of control specimens.
These results indicate that histamine may be related to the release of endogenous norepinephrine and its contractile response is mediated by H1 receptor on the terminal of the noradrenergic fiber and H1-, H2- and α-receptor on the vascular smooth muscle cell. From the results thus obtained, the role of histamine on adrenergic tonic control in allergic reaction was discussed briefly.
