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...

Pretreatment of Chinese hamster ovary cells expressing the histamine H2 receptor (CHOrH2 cells) with histamine resulted in a time-dependent (t1/2 approximately 7 h) and dose-dependent (EC50=18 nM) H2 receptor down-regulation measured as [125I]iodoaminopotentidine binding (44+/-10% down-regulation). Pretreatment of CHOrH2 cells with cholera toxin or forskolin also led to H2 receptor down-regulat...

In gastric parietal cells the histamine H2 receptor is involved in gastric acid secretion. Molecular cloning of the cDNA for the histamine H2 receptor has revealed that the receptor is a member of the G-protein coupled receptor family. We expressed histamine H2 receptors in CHO cells, COS7 cells, and Sf9 cells to analyze N-glycosylation, palmitoylation, and desensitization of the H2 receptor, w...

The role of histamine H1 and H2 receptors in the lung is not clear. H1 receptor blockade results in bronchodilatation and inhibition of histamine induced bronchoconstriction. H2 receptor blockade in vitro prevents the normal negative feedback of histamine on further mediator release in antigen challenge. Bronchospasm in guinea pigs given antigen challenge is enhanced by previous administration ...

The superior vestibular nucleus (SVN), which holds a key position in vestibulo-ocular reflexes and nystagmus, receives direct hypothalamic histaminergic innervations. By using rat brainstem slice preparations and extracellular unitary recordings, we investigated the effect of histamine on SVN neurons and the underlying receptor mechanisms. Bath application of histamine evoked an excitatory resp...

The recent development of a technique for quantitative measurement of conjunctival microvascular permeability has permitted detailed pharmacological evaluation of H1- and H2-receptor involvement in histamine-induced increases in conjunctival microvascular permeability and the role of histamine in microvascular permeability changes associated with immediate hypersensitivity responses in the conj...

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...

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...

  Objective(s): The present study investigated the effects of microinjection of histamine and histamine H1, H2, and H3 receptor antagonists, chlorpheniramine, ranitidine and thioperamide, respectively into the primary somatosensory cortex (PSC) on inflammatory pain.   Material and Methods: Two stainless steel guide canulas were bilaterally implanted into the PSC of anaesthetized rats. Inf...

To evaluate the ability of histamine to induce ventricular arrhythmias, we studied the effects of histamine on ventricular rhythmicity in the isolated guinea pig heart with complete atrioventricular conduction block. As a function of dose (0.1-30 microgram), histamine enhanced the idioventricular rate by increasing the rate of firing of the original pacemaker and also by causing the sudden appe...