Disease relevance of Hrh2

• The histamine H2 receptor agonist, dimaprit (10 mg kg(-1), i.v.), was also without effect on the evoked mydriasis [1].
• The effect of perivagal capsaicin treatment on gastric acid secretion induced by the histamine H2 receptor agonist, dimaprit dihydrochloride, and the effect of the histamine H1 receptor agonist, 2-thiazolylethylamine dihydrochloride, on gastric acid secretion were studied in acute gastric fistula rats anesthetized with urethane [2].
• In contrast, concomitant injection of the H2 receptor antagonist ranitidine (1 x 10(-8), 5 x 10(-8) mol) did not suppress the hyperglycemia induced by PGF2 alpha [3].
• The release of bioactive amines played an important role in mediating the TRAP-induced edema; the serotonin/histamine antagonist cryproheptadine and the histamine H2 receptor antagonist cimetidine reduced significantly the edema caused by TRAP [4].
• The effect of oral administration of synthetic human epidermal growth factor/urogastrone (EGF/URO) on healing of chronic duodenal ulcers induced by cysteamine in rats was investigated and compared with that of cimetidine, a H2-receptor antagonist [5].

Psychiatry related information on Hrh2

• The absence of selective, brain-penetrating H2-receptor agonists precludes a more detailed analysis of the role of this subtype of receptor in the control of sleep and wakefulness [6].
• The effect of intraperitoneal injections of cimetidine, a selective histaminergic H2-receptor blocking agent, on operant behavior and locomotor activity were examined in rats [7].
• A histaminergic H2-receptor antagonist, ranitidine, blocks the suppressive vasopressin response to fear-related emotional stress in the rat [8].
• Third ventricle injections of the H1 and H2 receptor antagonists, mepyramine (50, 100, 200 and 400 nmol) and cimetidine (100, 200 and 400 nmol), were unable to modify water intake induced by water deprivation and sodium depletion [9].

High impact information on Hrh2

• However, in the 2-week-old rat neither exogenous histamine nor the H-2 receptor agonist impromidine stimulates acid secretion, whereas pentagastrin and the cholinergic agent bethanechol are potent stimuli [10].
• At this age, the effect of pentagastrin in acid secretion is not blocked by the H-2 receptor antagonist cimetidine, nor is it potentiated by impromidine [10].
• Thus, histamine enhances cAMP accumulation specifically in mesangial cells via an H2 receptor [11].
• Therefore, H2 receptor activity may be permissive for the effect of gastrin on parietal cell function [12].
• METHODS: The superior mesenteric artery was occluded for 15 minutes followed by reperfusion, and H1- or H2-receptor antagonists were infused intraduodenally [13].

Chemical compound and disease context of Hrh2

• We studied the effects of the histamine H1 receptor antagonists diphenhydramine and pyrilamine, the H2 receptor antagonist ranitidine and the muscarinic receptor antagonist atropine injected into the third cerebral ventricle on prostaglandin F2 alpha (PGF2 alpha)-induced hyperglycemia in anesthetized fed rats [3].
• There is no evidence that loxtidine acts as a direct carcinogen and it is suggested that the tumours were the result of prolonged achlorhydria produced by a potent unsurmountable histamine H2 receptor antagonist [14].
• 1 The effects of the new H2-receptor antagonist famotidine, administered orally, on gastric secretion and emptying as well as on experimentally-induced gastric and duodenal ulcers were studied in the rat [15].
• Clonidine-induced hypotension: further evidence for a central interaction with histamine H2 receptor antagonists in the rat [16].
• Oxmetidine is an H2-receptor antagonist that has efficacy in the treatment of peptic ulcers [17].

Biological context of Hrh2

• We have screened a rat genomic library using DNA probes derived from the sequence of a recently cloned canine histamine H2 receptor (Gantz et al., Proc. Natl. Acad. Sci. USA 1991, 88, 429-433) [18].
• 6. The selective histamine H2-receptor agonist, 4-methyl histamine, had no effect on arterial blood pressure in doses which stimulated acid secretion [19].
• 6. The effects of histamine on synaptic transmission and PPD were mimicked by the selective H3 receptor agonist R-alpha-methylhistamine (0.1-10 microM) but not by the selective H2 receptor agonist dimaprit (10 microM) [20].
• However, the stimulatory effect of (R)-alpha-methylhistamine on water consumption was antagonised by thioperamide in a dose-dependent manner, whereas the H1 receptor antagonist mepyramine and the H2 receptor antagonist loxtidine were without effect [21].
• Effect of H1 and H2 receptor antagonists on the serum activity of gamma-glutamyltransferase during liver regeneration after partial hepatectomy in rats [22].

Anatomical context of Hrh2

• In different functional tests, the new antagonists showed high H3 receptor antagonist potencies in vitro (-log Ki values of 6.4-8.4) at synaptosomes of rat cerebral cortex and low activities at histamine H1 and H2 receptor subtypes [23].
• Pretreatment with cimetidine (a histamine H2 receptor antagonist) significantly thwarted the increases in the brain water content and the blood-brain barrier permeability [24].
• Capsaicin-sensitive vagal afferent fibers do not contribute to histamine H2 receptor agonist-induced gastric acid secretion in anesthetized rats [2].
• The uterine inhibitory responses to histamine and 4-methylhistamine (a histamine H2 receptor agonist) were similar in KCl-contracted uteri from progesterone- and oestrogen-treated rats [25].
• In the isolated rabbit thoracic aorta and guinea-pig trachea, alpha-mangostin inhibited histamine-induced contractions in a concentration-dependent manner in the presence or absence of cimetidine, a histamine H2 receptor antagonist [26].

Associations of Hrh2 with chemical compounds

• Histamine H2 receptor blockade with tiotidine (0.1 microM) slightly decreased, while thioperamide (1 microM), a selective histamine H3 receptor antagonist, did not block histamine-induced dilation [27].
• The specific histamine H3 receptor antagonist, clobenpropit (3.0 mg kg(-1), i.v.), blocked the inhibitory effect of R-alpha-methylhistamine, whereas neither the histamine H2 receptor antagonist, cimetidine (5.0 mg kg(-1), i.v.), nor the histamine H1 receptor antagonist, chlorpheniramine (0.5 mg kg(-1), i.v.), was effective [1].
• Mesenteric bed dilation initiated by histamine H2 receptor selective agonists, amthamine and dimaprit, were antagonized markedly by tiotidine [27].
• The hyperglycemic response to neurotensin was partially blocked by the histamine H-1 receptor blockers, diphenhydramine and promethazine, and by the H-2 receptor blocker, cimetidine [28].
• 4. When acid secretion was inhibited by the histamine H2-receptor antagonists, burimamide and metiamide, histamine still increased mucosal blood flow [19].

Physical interactions of Hrh2

• The effects of histamine H2 receptor antagonists on androgen action in vivo and dihydrotestosterone binding to the rat prostate androgen receptor in vitro [29].
• These new compounds bear a histamine H2 receptor antagonist (H2A) pharmacophore moiety attached to a gastrin receptor antagonist (GA) pharmacophore moiety in a reversed manner, namely the head-to-head manner, different from the previously reported head-to-tail manner [30].

Regulatory relationships of Hrh2

• Cell proliferation in dimethylhydrazine-induced colonic carcinomata was stimulated by histamine and by the histamine H2 receptor agonist dimaprit and inhibited by the histamine H2 receptor antagonists Metiamide and Cimetidine but not by the histamine H1 receptor antagonist Mepyramine [31].
• The HA-induced release of OT was inhibited by pretreatment with an H1 or an H2 receptor antagonist [32].
• Histamine H1 and H2 receptor activation stimulates ACTH and beta-endorphin secretion by increasing corticotropin-releasing hormone in the hypophyseal portal blood [33].
• The IL-1 beta-induced increase in permeability could be completely abrogated at 4 and 24 hours PI by treating the animals with the histamine H2-receptor antagonist ranitidine, which also reduced leukocyte infiltration by 47.2% [34].
• 3 In analogy with previous observations on other inhibitors of acid secretion we suggest that the H2-receptor antagonists stimulate gastrin release through their effect on acid secretion and that the raised serum gastrin level is responsible for the enzyme activation [35].

Other interactions of Hrh2

• The facilitatory effect of intra-CA1 histamine was mimicked by the histamine N-methyltransferase inhibitor SKF-91844 as well as by the H2 receptor agonist dimaprit and it was blocked completely by the H2 receptor antagonist ranitidine [36].
• These contractions were poorly inhibited by the histamine H1-receptor antagonist, mepyramine (1 and 10 microM) and insensitive to the histamine H2-receptor antagonist, cimetidine (10 microM), and to the cyclooxygenase inhibitor, indomethacin (5 microM) [37].
• The effect of compound 48/80 on plasma insulin-like growth factor I was significantly attenuated by oral administration of the histamine H1 receptor antagonist (chlorpheniramine), but not by the histamine H2 receptor antagonists (cimetidine and ranitidine) [38].
• HA, an H1 and an H2 receptor agonist, stimulated the OT secretion dose-dependently [32].
• Using a strategy based upon nucleotide sequence homology and starting from the sequence of the rat histamine H2 receptor (Ruat et al., Biochem. Biophys. Res. Commun. 1991, 179, 1470-1478), we have cloned a rat cDNA encoding a functional serotonin receptor (5-HT6) [39].

Analytical, diagnostic and therapeutic context of Hrh2

• Angiotensin I given through the lung caused an increased myotropic response in both assay when H2-receptor blocker was added to the perfusion medium [40].
• Effects of zolantidine a brain-penetrating H2-receptor antagonist, on naloxone-sensitive and naloxone-resistant analgesia [41].
• RT-PCR revealed that mRNA for the H1 receptor was expressed in 77% of isolated LC neurons, mRNA for the H2 receptor in 41% of LC neurons and H3 receptors in 29% [42].
• We have previously reported that cimetidine, a reference H2 receptor antagonist, attenuates the initial osteoclastic burst and subsequent trabecular bone loss induced by ovariectomy (ovx) in rats [43].
• Subcutaneous injection of the H2-receptor antagonist, burimamide, blocked these histamine effects and also of sinomeinine and aminoguanidine [44].

References