Histamine Receptor Type Research Articles

Hippocampal histamine receptors and conflictive exploration in the rat: studies using the elevated asymmetric plus-maze.

The possible role of histamine receptors in the hippocampal formation on the exploratory motivation and emotionality of the rat was studied. An elevated asymmetric plus-maze composed of 4 different arms (no walls, single high wall, high and low walls and two high walls) arranged at 90 degrees angles was used. The exploration score, considered to be an index of exploratory motivation, and the permanency score, considered to be an index of emotionality (anxiety), were determined. Histamine was administered locally into the ventral hippocampus at three different doses (9, 45 and 90 nmol). Another group of rats was also microinjected with 45 nmol of pyrilamine (a histamine H1 receptor antagonist) or ranitidine (a histamine H2 receptor antagonist) in addition to 9 nmol of histamine in order to identify the possible type of histamine receptor involved. Histamine administration significantly inhibited the exploration score and increased the permanency score at the doses of 9 and 45 nmol in two of four arms. These effects were completely blocked by the administration of either histamine receptor antagonist. The present results suggest that in the hippocampal formation histamine inhibits exploratory motivation and decreases emotionality by activating both types of histamine receptors. Also, the elevated asymmetric plus-maze appears to be a suitable technique to quantify exploration and possibly "anxiety".

Histamine inhibits tumor necrosis factor alpha release by mast cells through H2 and H3 receptors.

Histamine was one of the first inflammatory mediators thought to be important in the pathophysiology of asthma, but it is not now thought to be a mediator with primary importance in airway constriction. However, histamine has several effects that may be relevant. One of these effects, its immunoregulatory role, has been largely ignored in asthma. Thus, because mast cells (MC) are an important source of histamine and cytokines, the modulation by histamine of the release of one cytokine, tumor necrosis factor alpha (TNF alpha), was investigated. Rat peritoneal MC (PMC) were pretreated with different concentrations of histamine (10(-14) to 10(-4) M) for 2 h before being tested for their TNF alpha-dependent cytotoxicity. A concentration-dependent inhibition of cytotoxicity was observed from 21% at 10(-12) M to 38% at 10(-4) M, reaching a plateau at 10(-8) M. At least 1 h pretreatment with histamine or its presence throughout the cytotoxic assay was required for the inhibitory effect of histamine. This inhibition was abrogated by indomethacin or anti-PGE2, suggesting that PGE2 may be an important mediator in the inhibition of TNF alpha by histamine. To investigate the type of histamine receptor implicated in this effect, PMC were treated for 20 min with H1 (clemastine and diphenhydramine), H2 (ranitidine and cimetidine), or H3 (thioperamide) receptor antagonists before the addition of histamine. H2 or H3 antagonists abrogated the inhibitory effect of histamine on PMC TNF alpha-dependent cytotoxicity. Furthermore, blockage of H2 receptors with ranitidine increased the release of TNF alpha from PMC stimulated with antigen, suggesting that histamine released by MC within 10 min of antigen stimulation downregulates the subsequent release of TNF alpha from the same MC population. These results suggest that histamine may act as an autocrine regulator of cytokine release by MC and thus modulate inflammatory responses in allergic asthma.

Does histamine stimulate cyclic amp formation in the avian pineal gland via a novel (non-H 1, non-H 2, non-H 3) histamine receptor subtype

The effects of histamine (HA), and selective HA, H 1-, H 2 and H 3-receptor agonists on cyclic AMP formation were investigated in intact thick and duck pineal glands. HA potently stimulated the pineal cyclic AMP formation. The effect of HA was mimicked fully by Nα- methylated histamines, and partially by several histaminergic drugs: 2-thiazolylethylamine (H 1), amthamine (H 2) and Rα- methylhistamine (H 3). Dimaprit, another selective H 2-agonist showed marginal activity. Forskolin highly potentiated the action of HA, and only weakly affected the effects of 2-thiazolyethylamine and amthamine. In the chick pineal, the stimulatory effects of HA and the tested histaminergic drugs were not blocked by mepyramine and thioperamide (H 1- and H 3-blockers, respectively), but they were antagonized by H 2-receptor selective compounds ranitidine and aminopotentidine, which, however, acted in a noncompetitive manner. Another H 2-selective blocker zolantidine antagonized the HA effect only when used at very high (30–100 μM) concentrations. In the duck pineal, the stimulatory effect of HA on cyclic AMP production was unaffected by mepyramine (H 1), thioperamide (H 3), and ranitidine (H 2), and only partially inhibited by the H 2-blocker aminopotentidine. Electrophysiological experiments revealed that HA is capable of evoking inward currents in most of the tested cells acutely isolated from chick pineal gland. The present findings further indicate that the pharmacological profile of the avian pineal HA receptor, whose stimulation leads to activation of cyclic AMP production, is different from any known HA receptor type (H 1, H 2, H 3), and suggest the existence of either an avian-specific HA receptor, or a novel HA receptor subtype. Electrophysiological data suggest that the pineal HA receptor may be somehow linked to activation of an ionic channel.

Does histamine stimulate cyclic AMP formation in the avian pineal gland via a novel (non-H1, non-H2, non-H3) histamine receptor subtype.

The effects of histamine (HA) and selective HA H1-, H2 and H3-receptor agonists on cyclic AMP formation were investigated in intact chick and duck pineal glands HA potently stimulated the pineal cycle AMP formation. The effect of HA was mimicked fully by N alpha-methylated histamines, and partially by several histaminergic drugs: 2-thiazolylethylamine (H1) amthamine (H2) and R alpha-methyl-histamine (H3). Dimaprit, another selective H2-agonist showed marginal activity. Forskolin highly potentiated the action of HA, and only weakly affected the effects of 2-thiazolylethylamine and amthamine. In the chick pineal, the stimulatory effects of HA and the tested histaminergic drugs were not blocked by mepyramine and thioperamide (H1- and H3-blockers, respectively), but they were antagonized by H2-receptor selective compounds ranitidine and aminopotentidine, which, however, acted in a noncompetitive manner. Another H2-selective blocker zolantidine antagonized the HA effect only when used at very high (30-100 microM) concentrations. In the duck pineal, the stimulatory effect of HA on cyclic AMP production was unaffected by mepyramine (H1), thioperamide (H3), and ranitidine (H2), and only partially inhibited by the H2-blocker aminopotentidine. Electrophysiological experiments revealed that HA is capable of evoking inward currents in most of the tested cells acutely isolated from chick pineal gland. The present findings further indicate that the pharmacological profile of the avian pineal HA receptor, whose stimulation leads to activation of cyclic AMP production, is different from any known HA receptor type (H1, H2, H3), and suggest the existence of either an avian-specific HA receptor, or a novel HA receptor subtype. Electrophysiological data suggest that the pineal HA receptor may be somehow linked to activation of an ionic channel.

Intranasal histamine challenge in normality and allergic rhinitis

A series of investigations was performed in which histamine challenge was used to compare nasal responsiveness in 20 normal subjects and 20 with allergic rhinitis. There was found to be a lower threshold of reactivity (D100) to histamine in allergic subjects as measured by resistance changes (geometric mean, 0.53 mg/ml; normal subjects, 2.15: p = 0.022). This may represent increased number or sensitivity of histamine receptors on the nasal capacitance vessels. The loss of a laser Doppler response to a supramaximal histamine stimulus (normal subjects, 102% increase in flux at 3 minutes; p < 0.05) was observed in patients with allergic rhinitis and indicates either a down-regulation of the capillary system or an altered effect of histamine on superficial vessels, perhaps mediated by a shift in histamine receptor type. There was an observed increase in neutrophils at the mucosal surface under baseline conditions (rhinitis median, 49.6%; normal subjects, 32.72%: p < 0.05), which suggests an important primary role in the pathogenesis of this condition for this active cell. The observed increase in secretory volume response to histamine in allergic subjects, which persisted beyond 40 minutes after a single D100 challenge, may be related to an altered sensitivity of glandular tissue. There are important changes in nasal reactivity to histamine challenge in allergic rhinitis that may have implications for its pathogenesis.

P-356 - Histamine receptor type in guinea-pig left atrial muscles: change from H2 to H1 during postnatal development.

P-356 - Histamine receptor type in guinea-pig left atrial muscles: change from H2 to H1 during postnatal development.

In vivo occupancy of histamine H 3 receptors by thioperamide and ( R)- α-methylhistamine measured using histamine turnover and an ex vivo labeling technique

In the brain, the H 3 type of histamine receptor has a pre-synaptic autoreceptor inhibitory role which regulates neuronal release and synthesis of histamine. To examine the interaction of the selective H 3 receptor antagonist thioperamide with H 3 receptors in the brain in vivo, we have used a functional and non-functional measurement of H 3 receptor occupancy. In three species (rat, guinea-pig and mouse) peripheral administration of thioperamide caused dose-related increases in histamine turnover in the cerebral cortex (whole brain was examined in the mouse) and, in the same tissues, inhibited the ex vivo binding of the selective H 3 receptor agonist [ 3 H](R)-α- methylhistamine ([ 3 H]- RAMH) . The peak effect of thioperamide to inhibit ex vivo binding of [ 3H]RAMH was observed approximately 30 min after i.p. administration, whilst the maximum increase in histamine turnover did not occur until after at least 100 min. At a pretreatment time of 30 min, the ED 50 of thioperamide to inhibit ex vivo binding of [ 3H]RAMH binding in the rat, guinea-pig and mouse brain was found to be 2.0 ± 0.2, 4.8 ± 0.6 and 2.6 ± 0.3 mg/kg (mean ± SEM, N = 4), respectively. We have also examined the effect of peripheral administration of RAMH on ex vivo binding of [ 3H]RAMH in rat cortex. Qualitatively and quantitatively similar results to those of thioperamide were observed following i.p. administration of RAMH to rats (ed 50 = 3.9 ± 0.4 mg/kg, mean ± SEM, N = 4). An effect of RAMH on histamine turnover in rat cortex could not be determined as this compound displayed significant cross-reactivity with the antibodies used in the radioimmunoassay to measure histamine and telemethylhistamine. These data indicate that, following peripheral administration, both thioperamide and RAMH penetrate the brain where they can subsequently interact with H 3 receptors. It would appear that binding of thioperamide to H 3 receptors is linked with a concomitant increase in histamine turnover in the brain. In conclusion, the ex vivo binding technique, particularly when coupled with measurement of histamine turnover, should provide a valuable means for investigating the ability of any peripherally administered compound to cross the blood-brain barrier and subsequently interact with histamine H 3 receptors.

Treatment of hirsutism with cimetidine: a prospective randomized controlled trial

Cimetidine (Tagamet, Smith Klein, Brussels, Belgium) the histamine receptor type 2 blocker, has been suggested as a possible treatment of hirsutism. In a prospective randomized controlled trial, cimetidine 1.5 gm a day was given for 3 months to 12 moderately or severely hirsute women, while 8 other women were randomized to serve as a control group. There was no significant change in the hair growth rate in either group as measured by two assessment methods. This finding suggests that cimetidine, given in the recommended dose for a period of 3 months, does not have a beneficial effect on hirsutism.

DO YOUNG PATIENTS WITH DYSPEPSIA NEED INVESTIGATION?

During 1986, 1386 patients with simple dyspepsia were referred by general practitioners for endoscopy (686) or double-contrast barium meal examination (700) at Leicester General Hospital. 618 (45%) were under the age of 45 years. Abnormal findings were more common in older than younger dyspeptic patients (58% vs 40% at endoscopy, 69% vs 25% by barium meal). Malignant disorders were diagnosed in 5% at endoscopy and 3% at barium meal, but in no patient under 45 years old. The incidence of malignant disorders at endoscopy was analysed for the 6 years 1980-86. Of 707 cases identified, only 13 (1·8%) occurred in patients under 45 years old; all 13 had symptoms suggesting pathology more serious than simple dyspepsia. It can be concluded that young patients with simple dyspepsia are overinvestigated. A majority can be treated safely with antacids and/or histamine receptor type 2 antagonists.

The suppressive effect of histamine on anti-DNP antibody production in mice.

To clarify the effect of histamine on antibody production, histamine was injected intravenously into DNP-KLH immunized C3H/HeN female mice. The number of anti-DNP plaque-forming splenic cells decreased in immunized and histamine-injected mice. Decreased PFC responses similarly occurred in recipient mice into which Lyt-2.1 T cells obtained from histamine-injected mice were transferred before immunization. The effect of histamine is not due to inhibition on plaque formation. The results indicated that histamine induced the augmentation of suppressor T cell (Ts) function and caused the decrease of antibody production in histamine-injected mice. The maximum activity of Ts in recipient mice was obtained from mice injected with histamine 3 days before the cell transfer. The suppressive activity of histamine was not antigen specific because Ts was induced in histamine-injected, nonimmunized mice. The treatment of histamine type 2 (H2) agonist showed decreased PFC responses in the mouse as well as histamine did. When mice were treated with an H2 antagonist followed by histamine, antibody production was not reduced. The above results indicated that histamine seemed to regulate antibody production through H2 receptors on lymphocyte membranes.

Histamine and the heart.

Histamine has been known as a cardiac stimulant for over 70 years. Work in our laboratory over the past decade has established that histamine receptors exist in the hearts of various species. The type of histamine receptor varies not only between species but also in the various regions of the heart. In the guinea pig heart H1 receptors are found in left atria and ventricles while H2 receptors are found in right atria and are the predominant histamine receptor in the ventricles. Rabbit atria contain both H1 and H2 receptors while the ventricles appear to possess only H1. Rat and cat heart do not seem to have histamine receptors and the positive inotropic and chronotropic effects elicited by histamine in cardiac preparations of these species are due to the release of noradrenaline. Dog heart contains H1 receptors while human heart has H2 receptors. In all cases H2 receptors are associated with adenylate cyclase and stimulation of such receptors results in an increase in cyclic AMP levels. H1 receptors are not associated with cyclic nucleotides in the heart. There are certain similarities between beta-adrenergic and H2-histaminergic receptors as well as between alpha-adrenergic and H1-histaminergic receptors. Stimulation of either histamine receptor must result in an increase in the free calcium ion concentration in the cardiac cell but the mechanisms involved are obviously different.

Decrease in tumour growth by injections of histamine or serotonin in fibrosarcoma-bearing mice: influence of H1 and H2 histamine receptors.

C3H and C57 BL/6 mice carrying methylcholanthrene-induced fibrosarcomas were injected i.p. daily with histamine, metiamide (anti-histamine type-2 receptor), histamine + metiamide, mepyramine (anti-histamine type-1 receptor), serotonin and methysergide (anti-serotonin). Inhibition of tumour growth and lengthened survival were observed with histamine and histamine + metiamide. The best results (both on tumour growth and survival) were obtained with serotonin. Survival was increased by metiamide and decreased by mepyramine and methysergide. In histamine-treated and in serotonin-treated mice, histological studies of the tumours showed large and numerous foci of haemorrhagic necrosis. Stimulation of histamine type-1 or serotonin receptors and inhibition of histamine type-2 receptors play a beneficial role in the host's defence against tumours.

Relaxant responses of the isolated guinea-pig left pulmonary artery produced by acidic histamine solutions

Contractile responses to histamine were examined on left pulmonary arterial rings isolated from reserpine-pretreated guinea pigs. In the presence of mepyramine, contractile responses to histamine dihydrochloride and histamine diphosphate were preceded by concentration-dependent relaxant responses which were not blocked by metiamide. Hydrochloric acid also produced relaxation of the histamine- and noradrenaline-contracted vessels. Solutions of histamine dihydrochloride and histamine free base adjusted to about pH 7 did not produce the relaxant response. Changes in tissue bath pH were correlated with the relaxant responses produced by acidic histamine and hydrochloric acid solutions. Relaxation produced by histamine in this preparation is due to changes in tissue bath pH and not to activation of an atypical type of histamine receptor.

Histamine-Induced Suppressor Factor (HSF): Effect on Migration Inhibitory Factor (MIF) Production and Proliferation

Histamine added in vitro to cultures of sensitized lymphocytes suppresses antigen-induced production of migration inhibitory factor (MIF) and proliferation by these cells. Recent studies have suggested that lymphocytes bearing histamine type-2 receptors play a regulatory role in these in vitro responses. The present studies were undertaken to determine if suppressor function by cells having histamine receptors was mediated through a soluble product. It was found that lymph node cells from nonimmune or immune strain 2 guinea pigs elaborate a nondialyzable factor into the culture supernatant when incubated with 10(-3) to 10(-5) M histamine (histamine-induced suppressor factor of HSF). HSF, when cocultured with sensitized lymphocytes, suppressed their MIF and proliferative responses to antigen. HSF was made by lymphocytes but not macrophages. Its production could be blocked by an H2 receptor antagonist (burimamide) but not an H1 receptor antagonist (chlorpheniramine). Furthermore, the inhibitory effect of HSF was reversible as lymphocytes washed free of the factor after 24 hr and recultured with fresh medium and antigen were able to produce MIF. Gel filtration by Sephadex G-100 chromatography indicated that HSF had an approximate m.w. of 23,000 to 40,000. These results suggest that the release of histamine at the sites of immediate hypersensitivity reactions, possibly by generating HSF activity, may play a regulatory role in the subsequent development of cellular-immune reactions at the same site.

Histamine Modulation of Eosinophil Migration

Preincubation of eosinophils with 10(-5) M or higher concentrations of histamine inhibited the eosinophil chemotactic response to endotoxin-activated serum whether by using the nucleopore filter assay and counting the cells migrating through the filter, or by using the Zigmond-Hirsch assay and counting the cells at each 10-mum interval. When the H2-receptor sites on the eosinophils were blocked by metiamide, the inhibitory capacity of histamine was prevented. Preincubation of eosinophils with 10(-6) M histamine increased the number of responding eosinophils to endotoxin-activated serum and this enhancement was blocked by an H1-receptor antagonist. Isoproteronol and aminophylline inhibited eosinophil movement and increasing concentrations of dibutryl cyclic AMP inhibited eosinophil migration. Concentrations of histamine that consistently resulted in inhibition of eosinophil movement stimulated an increase in cyclic AMP that was prevented by blocking the H2-receptor but not the H1-receptor. Thus, histamine-dependent inhibition of the eosinophil chemotactic response to other agents is mediated through the H2-receptor and is associated with an increase in the intracellular level of cyclic AMP whereas histamine dependent enhancement of eosinophil migration to other agents appears to be mediated through the H1-receptor. Eosinophils behave as a heterogeneous population as assessed by the ability of histamine to augment or inhibit cell migration. This may reflect differences in H1 to H2 receptor density or cell responsiveness to receptor stimulation. The chemoattractant activity of histamine itself is not influenced by H1 or H2 receptor antagonists, thus it is possible that an eosinophil has a third type of histamine receptor.

Participation of H1 and H2 histamine receptors in physiological vasodilator responses.

Histamine causes vasodilation in the dog by activation of H1 and H2 receptors blocked by mepyramine and metiamide, respectively. Experiments were conducted in anesthetized dogs to determine the participation of H1 and H2 receptors in several forms of physiological dilatation. Mepyramine attenuated both histamine-induced and active-reflex dilatation in the hindlimb. Metiamide caused a further reduction in both sets of dilatation. Neither single nor combined antihistamines reduced dilatation due to exercise or after temporary occlusion of the circulation in the hindlimb. Poststimulation dilatation in the gracilis muscle was partially attenuated by metiamide or mepyramine. Neither dilatation caused by sympathetic nerve stimulation in the hindpaw nor dilatation in the gracilis muscle caused by compound 48/80 was reduced by mepyramine. Following combined H1- and H2-receptor blockade, portions of both types of dilatation were reduced. These data provide evidence for the participation of both types of histamine receptor in active reflex dilatation, low-frequency neurogenic dilatation, dilatation caused by compound 48/80, and poststimulation dilatation. Neither type of histamine receptor appears to be involved in reactive hyperemia or dilatation caused by exercise.

Editorial: Unrefined antihistamine lode.

A few months ago, an "Old Histamine Prospector" got all excited when he saw gold in them thar antihistamine hills. Indeed, he had maps showing where a rich lode of a new type of histamine antagonists might be found — agents that could inhibit gastric secretion by blocking a second type of histamine receptor symbolized by "H2".1 Equally jubilant on hearing of the discovery were many doctors and patients, the former weary of treating duodenal ulcers with dietary and antacid regimens, and the latter even more weary of observing them. But their ardor has been chilled by the . . .