Abstract
Histamine-induced contraction and its potentiation by neuropeptide Y were investigated in rat blood vessels. Rat arteries and veins constricted with single concentrations of histamine dose-dependently (0.1–100 μM). This histamine-induced contraction immediately desensitized. Histamine H 1 receptor antagonists, 1 μM mepyramine and 1 μM diphenhydramine, abolished this transient contraction completely, whereas cimethidine, phentolamine, reserpine and tetrodotoxin failed to inhibit the contraction. Histamine H 1 receptor mRNA level by reverse transcription-polymerase chain reaction was quite parallel to histamine H 1 receptor-mediated contraction, indicating that the contraction is mediated through histamine H 1 receptors in the smooth muscle. Neuropeptide Y (10 nM in arteries and 3 nM in veins, respectively) significantly potentiated histamine H 1 receptor-mediated contraction via neuropeptide Y 1 receptors in most of rat blood vessels. Since the phospholipase C inhibitors, neomycin (1 mM) and 2-nitro-4-carboxyphenyl- N, N-diphenylcarbamate (NCDC, 10 μM), respectively, specifically abolished the potentiation, the potentiation by neuropeptide Y may depend on activation of phospholipase C.
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