Histamine elevates the intracellular cyclic AMP levels in cultured embryonic chick retinal pigment epithelium. The half-maximal activity is 6 X 10(-6) M. The effect of histamine is mediated by H2 receptors, i.e., inhibited by the H2 antagonist cimetidine and not affected by the H1 antagonists diphenhydramine and pyrilamine. The inhibition constant (KI) of cimetidine is 1.3 X 10(-8) M. Thus, the...

Sunburn, wound repair, and chronic renal failure with hemodialysis are usually accompanied by both pigmentation and itching. Proopiomelanocortin-derived α-melanocyte-stimulating hormone (α-MSH) is produced in response to external stimuli, such as UV irradiation, and is involved in cutaneous pigmentation. However, it is unclear whether α-MSH is also involved in the itching. We therefore investig...

Few drugs have so rapidly gained an established place in modern medicine as the histamine H, receptor antagonists. As a result of the inventiveness of James Black and his colleagues, the theoretical concept of a second class of histamine receptors became a therapeutic reality. The failure of classic antihistamine drugs (more appropriately H1 receptor antagonists) to block the actions of histami...

Evidence suggests that central histaminergic neurons make important contributions to cardiovascular regulation. For example, histamine-containing neurons project to brain regions important for cardiovascular regulation. Furthermore, stimulation of central histamine receptors changes blood pressure and heart rate and alters activity of major vasoconstrictor systems. Finally, histamine metabolism...

Histamine caused a fall in blood pressure in anesthetized dogs and cats which was only partially attenuated by mepyramine (pyrilamine), a histamine type H1-receptor antagonist. Further treatment with burimide or metiamide, type H2-receptor antagonists, caused nearly complete attenuation of the response to histamine. Burimamide alone had no effect on vasodilatation produced by histamine in the d...

We examined the effects of histamine and its agonists on the expression of the c-fos and c-myc proto-oncogenes at the transcriptional and translational levels in the human promonocytic U937 cell line. Histamine transiently increased cAMP and c-fos expression through H2 receptors. Dibutyryl cAMP also increased c-fos mRNA and protein, and levels remained elevated even after 12 hr of treatment. Do...

The determinants for recognition at H3 histamine receptors are considered. Findings based on quantum-chemical calculations suggest that H3 histamine receptor is less hydrophilic than the H2. The form most likely to be recognized by the H3 receptor is an intramolecularly hydrogen-bonded form of alpha-methylhistamine. Receptor environment and hydration effects of active form of histamine analogs ...

Using specific histamine H1 and H2 receptor antagonists, evidence is presented for the existence of both H1 and H2 receptors on human articular chondrocytes in vitro. Stimulation of the H1 receptor by histamine (range 0.18 to 17.8 mumol/l) significantly increased prostaglandin E (PGE) production, while activation of the histamine H2 receptor increased intracellular cyclic adenosine-5'-monophosp...

1 Histamine and 2-methyl-histamine (H1-receptor agonist) caused dose-dependent increases in capillary permeability in albino mice, but 4-methyl-histamine (H2-receptor agonist) caused no significant increase. 2 Mepyramine (H1-receptor antagonist) blocked the histamine-induced increase in capillary permeability whereas burimamide (H2-receptor antagonist) produced no significant blockade of the hi...