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Histamine H4 receptor antagonists as potent modulators of mammalian vestibular primary neuron excitability.

ABSTRACT: BACKGROUND AND PURPOSE:Betahistine, the main histamine drug prescribed to treat vestibular disorders, is a histamine H(3) receptor antagonist. Here, we explored the potential for modulation of the most recently cloned histamine receptor (H(4) receptor) to influence vestibular system function, using a selective H(4) receptor antagonist JNJ 7777120 and the derivate compound JNJ 10191584. EXPERIMENTAL APPROACH:RT-PCR was used to assess the presence of H(4) receptors in rat primary vestibular neurons. In vitro electrophysiological recordings and in vivo behavioural approaches using specific antagonists were employed to examine the effect of H(4) receptor modulation in the rat vestibular system. KEY RESULTS:The transcripts of H(4) and H(3) receptors were present in rat vestibular ganglia. Application of betahistine inhibited the evoked action potential firing starting at micromolar range, accompanied by subsequent strong neuronal depolarization at higher concentrations. Conversely, reversible inhibitory effects elicited by JNJ 10191584 and JNJ 7777120 began in the nanomolar range, without inducing neuronal depolarization. This effect was reversed by application of the selective H(4) receptor agonist 4-methylhistamine. Thioperamide, a H(3) /H(4) receptor antagonist, exerted effects similar to those of H(3) and H(4) receptor antagonists, namely inhibition of firing at nanomolar range and membrane depolarization above 100?µM. H(4) receptor antagonists significantly alleviated the vestibular deficits induced in rats, while neither betahistine nor thioperamide had significant effects. CONCLUSIONS AND IMPLICATIONS:H(4) receptor antagonists have a pronounced inhibitory effect on vestibular neuron activity. This result highlights the potential role of H(4) receptors as pharmacological targets for the treatment of vestibular disorders.

SUBMITTER: Desmadryl G

PROVIDER: S-EPMC3575788 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

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Histamine H4 receptor antagonists as potent modulators of mammalian vestibular primary neuron excitability.

Desmadryl G G Gaboyard-Niay S S Brugeaud A A Travo C C Broussy A A Saleur A A Dyhrfjeld-Johnsen J J Wersinger E E Chabbert C C

British journal of pharmacology 20121001 4

<h4>Background and purpose</h4>Betahistine, the main histamine drug prescribed to treat vestibular disorders, is a histamine H(3) receptor antagonist. Here, we explored the potential for modulation of the most recently cloned histamine receptor (H(4) receptor) to influence vestibular system function, using a selective H(4) receptor antagonist JNJ 7777120 and the derivate compound JNJ 10191584.<h4>Experimental approach</h4>RT-PCR was used to assess the presence of H(4) receptors in rat primary ve ...[more]

PMID: 22624822

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Project description:The histamine H4 receptor (H4R) was first noted as a sequence in genomic databases that had features of a class A G-protein coupled receptor. This putative receptor was found to bind histamine consistent with its homology to other histamine receptors and thus became the fourth member of the histamine receptor family. Due to the previous success of drugs that target the H1 and H2 receptors, an effort was made to understand the function of this new receptor and determine if it represented a viable drug target. Taking advantage of the vast literature on the function of histamine, a search for histamine activity that did not appear to be mediated by the other three histamine receptors was undertaken. From this asthma and pruritus emerged as areas of particular interest. Histamine has long been suspected to play a role in the pathogenesis of asthma, but antihistamines that target the H1 and H2 receptors have not been shown to be effective for this condition. The use of selective ligands in animal models of asthma has now potentially filled this gap by showing a role for the H4R in mediating lung function and inflammation. A similar story exists for chronic pruritus associated with conditions such as atopic dermatitis. Antihistamines that target the H1 receptor are effective in reducing acute pruritus, but are ineffective in pruritus experienced by patients with atopic dermatitis. As for asthma, animal models have now suggested a role for the H4R in mediating pruritic responses, with antagonists of the H4R reducing pruritus in a number of different conditions. The anti-pruritic effect of H4R antagonists has recently been shown in human clinical studies, validating the preclinical findings in the animal models. A selective H4R antagonist inhibited histamine-induced pruritus in health volunteers and reduced pruritus in patients with atopic dermatitis. The history to date of the H4R provides an excellent example of the deorphanization of a novel receptor and the translation of this into clinical efficacy in humans.

Project description:Hemorrhagic shock has a potential to be life-threatening when it is not treated. The main causes of hemorrhagic shock involve: (1) forces causing injury; and (2) diseases that can cause hemorrhage., Therefore, due to the causes of hemorrhagic shock and the life-threatening potential, the search for new methods of shock treatment is extremely valuable to the modern medicine. The aim of this study was to investigate the influence of clobenpropit in the model of hemorrhagic shock. The experiments were conducted in 110 adult male Wistar rats weighing between 205 and 470g. 1, 2 and 5 ?mol/kg of intravenous H3 receptors reverse agonists, clobentropit, and/or 1, 5 and 10 ?mol/kg H3 receptor agonist, imetit, were used as general anesthetics. Irreversible hemorrhagic shock was induced by the paused bleeding until the mean arterial pressure (MAP) lowered to the level of 20-25 mmHg. It was proved that, in cases of critical hypotension, clobenpropit triggered a dose-dependent increase of: systolic blood pressure (SBP), diastolic blood pressure (DBP), MPA and heart rate (HR) of rats with critical hypotension. The most significant changes in hemodynamic parameters were achieved by administrating dosages of 2 mmol/kg. This resulted in the survival rate increase to up to 100%. However, imetit did not trigger any hemodynamic changes nor an increase in SBP, DBP, MAP or HR. Furthermore, it was found that the premedication with prazosin, yohimbine, 6-hydroxydopamine and the vasopressin V1a receptor antagonist blocked the effects of clobenpropit. Additionally, premedication with propranolol, captopril and ZD 7155 did not cause any significant changes in the measured hemodynamic parameters. In conclusion, after an intravenous injection clobenpropit, the inverse agonist of H3 histamine receptors/agonist of histamine receptors H4, causes a resuscitating effect on rats in hemorrhagic shock. Moreover, such effect is based on the effector mechanisms of sympathetic nervous system and vasopressin.

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Histamine H4 receptor antagonists as potent modulators of mammalian vestibular primary neuron excitability.

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Histamine H4 receptor antagonists as potent modulators of mammalian vestibular primary neuron excitability.

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