The role of histamine H1 receptor in the anterior cingulate cortex on nociception level following acute restraint stress in male rats

Considering the importance of pain and stress, we decided to investigate the intra-anterior cingulate cortex (ACC) microinjection of histamine and mepyramine alone and concurrently on acute pain induced by hot plate following restraint stress in male rats. 24-gauge, 10 mm stainless steel guide cannula was implanted over the ACC in the incised scalp of 4 groups. Restraint stress in healthy rats produced a significant increase (p < .05) in the pain threshold. The simultaneous microinjection of 4 μg/side histamine and 8 μg/side mepyramine as a histaminergic system inverse agonist in healthy nonrestraint animals did not affect the pain threshold. Although Histamine decreased the threshold of pain meaningfully, mepyramine elevated it in a significant manner (p < .05). In the restrained animals, intra-ACC microinjection of histamine produced no significant impact on the pain threshold. However, intra-ACC microinjection of mepyramine before histamine, significantly (p < .01) altered the result and enhanced the threshold of pain. The results of our study demonstrated that histaminergic neurons have an important role in the processing of pain in the ACC following restraint stress.

[Research progress of pyrilamine-sensitive H~+/OC antiporter]

In recent years, a new type of organic cation transporter has been found to transport organic cation drugs like pyrilamine, diphenhydramine and oxycodone in brain capillary endothelial cells, Caco-2 cells and other cells. Its transport activity can not be inhibited by typical organic cation transporter substrates or inhibitors, and its transport characteristics are different from those reported for the organic cation transporters, such as organic cation transporters (OCTs), organic cation/carnitine transporters (OCTNs), multidrug and toxin extrusion transporters (MATE) and the plasma membrane monoamine transporter (PMAT). It is a novel organic cation transporter, called pyrilamine-sensitive H(+)/OC antiporter. This review will present a comprehensive summary to elaborate the transport characteristics, structure of the substrates, tissue expression and the differences with other organic cation transporters.

Striking differences of action of lisuride stereoisomers at histamine H1 receptors

This study has characterised the pharmacological profile of some dopaminergic agents of the ergoline family including the antiparkinsonian drug 8S-lisuride at native guinea pig histamine H(1) receptors and recombinant human and guinea pig H(1) receptors. We used segments of guinea pig ileum to study contractile responses, Sf9 insect cell membranes expressing the guinea pig H(1) receptor (gpH(1)R) and the human H(1) receptor (hH(1)R) to analyse GTPase activity of G(q)-proteins and we conducted [(3)H]mepyramine binding studies using recombinant gpH(1)Rs and hH(1)Rs. 8S-Lisuride acted as a potent partial agonist at H(1)Rs of guinea pig ileum (pD(2) 7.6, E (max) 28% of histamine-induced maximum response) and as a silent antagonist at recombinant gpH(1)Rs (pA(2) 7.5) and hH(1)Rs (pA(2) 7.7) in GTPase studies. In contrast, its epimeric counterpart, 8R-lisuride, lacked efficacy and showed much lower affinity for H(1)Rs of both species than 8S-lisuride. High affinity of 8S-lisuride and low affinity of 8R-lisuride was also estimated for gpH(1)Rs and hH(1)Rs in radioligand binding studies. The 1-allylated derivative of 8S-lisuride, 1-allyl-8S-lisuride, was equipotent with its parent compound (pD(2) 7.7) and showed enhanced efficacy in guinea pig ileum and at recombinant gpH(1)Rs in GTPase studies (E (max) 53%, 32%). Other antiparkinsionian drugs such as 8S-terguride, pergolide, cabergoline and bromocriptine displayed lower affinities for H(1)Rs than 8S-lisuride. In conclusion, our results show that the antiparkinsonian drug 8S-lisuride is dramatically more potent than its epimeric counterpart 8R-lisuride in all assays used. 8S-Lisuride behaved as a partial agonist at gpH(1)Rs and as a silent antagonist at hH(1)Rs. Thus 8S-lisuride may act as an antagonist in vivo. This may be of potential importance since H(1)Rs modulate dopaminergic transmission in the brain.

A novel phenylaminotetralin radioligand reveals a subpopulation of histamine H(1) receptors

Previously, (-)-trans-1-phenyl-3-N,N-dimethylamino-1,2,3,4-tetrahydronaphthalene ([-]-trans-H(2)-PAT) was shown to activate stereospecifically histamine H(1) receptors coupled to modulation of tyrosine hydroxylase activity in guinea pig and rat forebrain in vitro and in vivo. Furthermore, the novel radioligand [(3)H](-)-trans-H(2)-PAT was shown to label selectively H(1) receptors in guinea pig and rat brain with high affinity (K(D), ~0.1 and 0.5 nM, respectively) and a B(max) about 50 and 15%, respectively, of that observed for the H(1) antagonist radioligand [(3)H]mepyramine. In the current study, [(3)H](-)-trans-H(2)-PAT-labeled cloned guinea pig and human H(1) receptors in Chinese hamster ovary (CHO) cell membranes with high affinity (K(D), ~0.08 and 0.23 nM, respectively) and a B(max) about 15% of that observed for [(3)H]mepyramine. The binding of H(2)-PAT to H(1) receptors in both CHO-H(1) cell lines was stereoselective with the (-)-trans-isomer having affinity (K(i), ~1.5 nM) about 4-, 20-, and 50-times higher than the (-)-cis-, (+)-trans-, and (+)-cis-isomers, respectively; the affinity of (-)-trans-H(2)-PAT was unaffected by excess GTP. In functional assays, (-)-trans-H(2)-PAT was a full antagonist of histamine H(1)-mediated stimulation of phospholipase C (PLC) and [(3)H]inositol phosphates (IP) formation in CHO-H(1) cells, a full inverse agonist of constitutively active H(1) receptors in COS-7-H(1) cells, and a full competitive antagonist (pA(2) = 9.2) of histamine H(1)-mediated contraction of guinea pig ileum. It is concluded that (-)-trans-H(2)-PAT is an antagonist at H(1) receptors coupled to PLC/IP formation and smooth muscle contraction. Meanwhile, the observation that [(3)H](-)-trans-H(2)-PAT labels only a subpopulation of H(1) receptors and that (-)-trans-H(2)-PAT activates H(1) receptors coupled to modulation of tyrosine hydroxylase suggests that there may be post-translational H(1) receptor heterogeneity.

Comparison of cedar pollen-induced allergic rhinitis in passively and actively sensitized guinea pigs

We have developed an allergic rhinitis model in guinea pigs using Japanese cedar pollen as antigen. In the present study, we examined whether provocation by pollen induces similar magnitudes of rhinitis symptoms in passively and actively sensitized guinea pigs. One group of animals was actively sensitized by intranasal application of pollen extract, and another was passively sensitized by intraperitoneal injection with anti-pollen serum. Actively and passively sensitized groups were then challenged by repeated and a single pollen inhalation, respectively. In both groups, sneeze was induced immediately after the challenge. The actively sensitized animals developed not only early but also late nasal blockage, whereas the passively sensitized animals showed only early nasal blockage. In both groups, an H1 antagonist, mepyramine, inhibited the occurrence of sneezing but did not inhibit nasal blockage. Nasal hyperresponsiveness to intranasal instillation of leukotriene D4 was obvious only in the actively sensitized animals. We thus conclude that although early nasal blockage is induced by a single antigen-antibody reaction, repetitive anaphylactic reaction is required for occurrence of late nasal blockage and hyperresponsiveness to stimuli. Furthermore, histamine plays a central role in induction of sneezing but not in nasal blockage, irrespective of whether animals are actively or passively sensitized.

QSAR study on binding affinity of PATs (rodenticides) to the [3H]-mepyramine-labelled H1 receptor in rat and guinea pig brain

The binding of a series of PAT analogues (rodenticides) to the [3H]-mepyramine-labelled H1 receptor in rat and guinea pig brain was investigated topologically using negentropy (N), molecular redundancy (MRI), first-order molecular connectivity (1chi(v)), Wiener (W), and Szeged (Sz) indices. Multiple regression analyses showed that MRI provided excellent results upon introduction of indicator parameters. Predictive ability of the proposed models was discussed using cross-validation parameters.

Some inhibitors of histamine-induced and formaldehyde-induced inflammation in mice

The swelling and capillary hyperpermeability of the mouse foot in response to an injection of formaldehyde, and the increased capillary permeability to an intradermal injection of histamine, have been investigated. Cortisone, mepyramine and sodium salicylate were effective in reducing histamine-induced inflammation, sodium salicylate being less active in the adrenalectomized animal. In formaldehyde-induced inflammation, however, cortisone was ineffective whereas sodium salicylate was effective in the intact mouse, but not in the adrenalectomized animal. Certain aryloxypropionates and anti-esterases were also active in reducing the severity of the formaldehyde-induced inflammation.

On the nature of the chemical mediators involved in anaphylactic reactions in mice

The effects of mepyramine, promethazine, chlorpromazine and lysergic acid diethylamide have been compared on the capillary permeability changes of the skin, produced by histamine, by 5-hydroxytryptamine and by passive cutaneous anaphylaxis in mice. Promethazine, mepyramine and chlorpromazine can inhibit, in decreasing order of activity, the effect of histamine, whilst lysergic acid diethylamide is inactive. Lysergic acid diethylamide and chlorpromazine are equally potent inhibitors of the action of 5-hydroxytryptamine on the peripheral vascular bed, whilst mepyramine is inactive. Promethazine has intermediate activity. Passive cutaneous anaphylaxis is strongly inhibited by chlorpromazine and by promethazine. Mepyramine and lysergic acid diethylamide, each injected alone, affect only weakly the anaphylactic reaction. However, passive cutaneous anaphylaxis is almost completely abolished by the simultaneous injection of the two last antagonists. It is suggested that the anaphylactic reaction in mice is the result of simultaneous release of both mediators, histamine and 5-hydroxytryptamine, each of them strengthening the effect of the other.

STIMULANT ACTIONS OF VOLATILE ANAESTHETICS ON SMOOTH MUSCLE

A number of volatile anaesthetics, and some compounds synthesized in the search for new anaesthetics, have been tested on guinea-pig intestinal smooth muscle in vitro. All the compounds produced a contractile response. This effect did not correlate well with convulsant activity in vivo among the compounds tested. Two kinds of stimulant effect were distinguishable: (1) Rapid, transient contractions, abolished by cocaine or lachesine; most of the anaesthetics in clinical use had this action. (2) Slow, sustained contractions, unaffected by cocaine or lachesine; this effect predominated among the fluorinated ring compounds. Hexamethonium and mepyramine did not affect the contractile response to any of the compounds. The first type of effect presumably represents excitation of postganglionic nerve cells, while the second type is a direct action on the muscle cell. The action of perfluorobenzene, which is of the latter kind, was studied further. Adrenaline and lack of calcium diminished the contraction in parallel with the contraction to histamine, which suggests that the cell membrane was the site of action; in contrast to the stimulant action of histamine or acetylcholine, the effect was highly temperature-sensitive, being almost abolished by cooling to 32 degrees C, and enhanced at 40 degrees C. The depressant action of anaesthetics on smooth muscle is affected very little by temperature changes. These findings are discussed in relation to other observations which suggest a stimulant action of volatile anaesthetics on excitable tissues. Protein denaturation is tentatively suggested as a mechanism of action.

Characterization and autoradiographic localization of histamine H1 receptors in human nasal turbinates

To examine the localization of histamine H1 receptors (H1R) in human nasal mucosa, the autoradiographic distribution of H1R was studied in human nasal inferior turbinates. Cryostat sections were incubated with various concentration of [3H]pyrilamine in saturation-binding studies and with 1 nmol/L of [3H]pyrilamine for autoradiography. Nonspecific binding was determined by adding 2 mumol/L of pyrilamine. Scatchard analysis demonstrated high-affinity binding sites with a maximum binding capacity of H1R of 193 +/- 46 fmol/mg of protein, and dissociation constant was 0.6 +/- 0.1 nmol/L. Autoradiograms indicated H1R exist exclusively on the endothelium of vessels. No specific labeling could be observed in the submucosal glands or epithelium. These results extend and support our previous finding that histamine directly causes vascular permeability through H1R and stimulates nasal glandular secretion indirectly through reflexes.

Inhibitory effect of NZ-107 on anaphylactic bronchoconstriction in guinea pigs and rats

We studied the effect of NZ-107 in a number of animal models of anaphylactic bronchoconstriction. In conscious guinea pigs, pretreated with indomethacin, pyrilamine and propranolol, passively sensitized with heterologous anti serum, NZ-107 in doses of 10-30 mg/kg per os inhibited the aerosolized antigen-induced cough and collapse. NZ-107 in a high dose of 100 mg/kg per os significantly prevented aerosolized antigen-induced anaphylactic collapse, but not cough in actively or passively sensitized conscious guinea pigs and also significantly protected aerosolized histamine-induced collapse, but not cough in conscious guinea pigs. This compound had little inhibitory effect on aerosolized acetylcholine-induced cough and collapse. In anesthetized animals, the effect of NZ-107 on bronchoconstriction induced by intravenous administration of antigen and various agonists was examined by the method of Konzett and Rössler. In doses of 10-50 mg/kg per os, NZ-107 inhibited antigen-induced bronchoconstriction in anesthetized guinea pigs. NZ-107 when intravenously administered to the anesthetized guinea pigs inhibited not only leukotriene D4-induced bronchoconstriction, but also thromboxane A2 mimetic U-46619-, platelet-activating factor- and histamine-induced bronchoconstriction. In anesthetized rats, NZ-107 in a dose of 300 mg/kg per os tended to inhibit the antigen-induced bronchoconstriction, but this effect was not significant. These results indicate that NZ-107 acts as a spasmolytic agent which inhibits bronchial responses to antigens or various other bronchoconstrictors in animal models, suggesting that NZ-107 may be potentially beneficial in the treatment of bronchial asthma.

Histamine induces endothelium-dependent relaxation of bovine retinal arteries

The effect of histamine on bovine isolated retinal small arteries (internal diameter, approximately 240 microns) was studied. Histamine induced a concentration-dependent relaxation in 43 of 53 vessels. The histamine-induced relaxation involves primarily activation of H1-receptors, with H2-receptors also affected as evidenced by the effect of selective histamine-receptor agonists and antagonists. The histamine-induced relaxation was dependent on the endothelium and seem to involve release of both endothelium-derived relaxing factor (EDRF) and a product which was inhibited by indomethacin, probably prostaglandin I2 (prostacyclin). The development of tachyphylaxis to the action of histamine seemed to rely on desensitization of the vascular smooth muscle cells to the relaxing effect of EDRF.

Substance P induced hydrolysis of inositol phospholipids in rat skin in an in vivo model of inflammation

The present study was undertaken to study the ability of substance P (SP) to induce inositol phospholipid (IP) hydrolysis measured as inositol mono-phosphate (IP1) accumulation, in an in vivo blister model of neurogenic inflammation in the rat hind footpad. SP was found to induce IP1 accumulation in a concentration dependent manner. The use of SP analogues (SP5-11 and SP1-7) indicated that the response is mainly mediated by the C-terminal sequence of the peptide. The response was significantly reduced by the SP antagonist spantide, suggesting that the response is mostly due to activation of the SP receptor on small diameter vessels. Capsaicin pretreatment did not have an effect on the ability of SP to induce the response. Experiments with mepyramine suggest that the response is also partly mediated by SP induced histamine release from mast cells. This is the first study to provide direct evidence for phosphoinositide mediated SP effects in the skin.

Characterization of histamine H1-receptor on rat hepatocytes

The binding sites for [3H]pyrilamine in isolated rat hepatocytes were characterized. Scatchard analysis revealed two kinds of binding sites in hepatocytes, a high-affinity site and a low-affinity one. The rates of binding of the radioligand with the high-affinity binding site and its dissociation were rapid. The specificity of the sites for various histamine antagonists indicated that the high-affinity [3H]pyrilamine binding site is representative of the histamine H1 receptor. Treatment of hepatocytes with protease or phospholipase A2 significantly decreased the maximum binding capacity of the high-affinity site without affecting its dissociation constant, suggesting that the binding site is proteinaceous and is sensitive to a change in the lipid moiety of the membrane. Hepatocytic cyclic AMP and cyclic GMP were not significantly modulated by incubating hepatocytes with histamine. Thus, the action of histamine on hepatocytes might not be mediated by the cyclic nucleotides.

Distribution of neurotransmitter binding sites in the cat median eminence

Receptor autoradiography was used to determine the distribution of binding sites for monoaminergic and cholinergic neurotransmitters in the cat median eminence. Results showed that binding sites were differentially distributed in that [3H]-p-aminoclonidine (an alpha-2-adrenergic ligand) and [3H]pyrilamine (an H1-histaminergic ligand) binding were concentrated in the medial region of the external layer of the median eminence while [3H]lysergic acid diethylamide (a serotonergic ligand) and [3H] quinuclidinyl benzilate (a muscarinic cholinergic ligand) binding were concentrated within the lateral region of the external layer. These patterns are coincident with the differential distribution of hypophysiotropic hormones in the median eminence, suggesting that monoamines and acetylcholine may regulate the release of these hormones at the level of the median eminence.

Experimental renal anaphylaxis: release of histamine and study of its effect on renal perfusion

Antigen challenge of isolated perfused kidneys of sensitized guinea-pigs consistently released a large proportion of their histamine content, and caused a reduction in renal perfusate flow rate (RPFR) which could not simply be due to the released histamine, since much larger amounts of exogenous histamine were needed to produce a comparable effect. Reduction in RPFR by histamine was blocked by mepyramine but not by cimetidine, i.e. it is mediated by an H1-receptor mechanism.

Carcinogenicity studies of some analogs of the carcinogen methapyrilene in F344 rats

Four antihistaminic drugs similar in structure to the rat liver carcinogen methapyrilene were administered to comparable groups of male and female F344 rats in their drinking water for most of their lifetime (80-108 weeks). The concentrations were 0.1% or 0.05% and the total doses received by the animals were comparable with that of methapyrilene which induced 100% incidence of liver neoplasms. No increase in incidence of liver neoplasms was observed after treatment with any of the four compounds, thenyldiamine, chlorothen, methafurylene, or methaphenilene, although each differed structurally from methapyrilene only in one atom or one position of substitution. There were a few animals with neoplasms not usually found in untreated F344 rats, but none of these was found in statistically significant numbers. These results suggest that none of the four analogs of methapyrilene was carcinogenic under the conditions of this study, and that the property of inducing liver neoplasms in rats was confined to the intact methapyrilene molecule.

Carcinogenicity of methapyrilene hydrochloride, mepyramine hydrochloride, thenyldiamine hydrochloride, and pyribenzamine hydrochloride in Sprague-Dawley rats

Four histamine antagonists, methapyrilene, thenyldiamine, mepyramine and pyribenzamine were tested for carcinogenicity in rats by continuous application in drinking water. Only methapyrilene displayed significant carcinogenic effects, inducing liver tumors in a dose-related pattern. Analogues not containing a thiophene ring (mepyramine, pyribenzamine) did not exhibit neoplastic effects under the experimental conditions.

Restraint stress stimulation of prolactin and ACTH secretion: role of brain histamine

The possible role of brain histamine in the release of prolactin, ACTH and corticosterone following acute restraint, was pharmacologically evaluated in adult male rats. Fifteen min of restraint caused marked increases in the plasma levels of these hormones. alpha-Fluoromethyl histidine (FH), a histidine decarboxylase inhibitor which depleted hypothalamic histamine, inhibited the enhancement of plasma prolactin levels. In contrast, plasma ACTH levels were not modified. FH treatment decreased plasma corticosterone concentrations in animals submitted to stress or in rest; this suggests a direct action of FH on the adrenal. Intraventricular (IVT) injection of ranitidine (H2 antagonist) blunted the prolactin response to restraint stress whereas its systemic administration had no effect. On the contrary, pyrilamine (H1 antagonist) given systemically decreased slightly, but significantly, the prolactin rise but when injected IVT it was ineffective. Pyrilamine was also unable to affect the ranitidine action. ACTH and corticosterone levels in plasma of restrained rats were not modified by the histamine antagonists. It is concluded that histamine is involved, mainly through central H2 receptors, in the enhancement of plasma prolactin levels produced by an acute stress. The failure of both antihistaminic compounds and a histamine depletor to alter the ACTH stimulation suggest that histamine has no participation in the hypophysio-corticoadrenal response to acute restraint.

Effect of pH on the micellar properties of amphiphilic drugs in aqueous solution

The influence of pH on the micellar properties of several amphiphilic drugs under conditions of constant ionic strength has been investigated. No significant effect of pH on the critical micelle concentration or micellar size of chlorpromazine hydrochloride was noted over a pH range well below the pKa. The micellar properties of opipramol, thiopropazate, flupenthixol, clopenthixol, and trifluoperazine, which contain a piperazine moiety showed considerable pH dependence. The concentration dependence of the pKa in these micellar systems was taken into consideration in the selection of pH values representative of complete protonation of either one or both of the piperazine N atoms. A lower aggregation number and higher critical micelle concentration was observed at a low pH corresponding to complete protonation of both charge centres. Mepyramine maleate exhibited a non-micellar mode of association at pH 5.5 which could be described by a stepwise association model in which association constants, KN, increased sequentially with aggregation number. N, according to the relationship, KN = K(N - 1)/N where K = 31.3 dm3mol-1. No significant association could be detected at pH 2 when the pyridine ring N was fully protonated.

Autoradiographic localization of H1-histamine receptors in brain using 3H-mepyramine: preliminary studies

3H-Mepyramine (3H-MEP) binds to slide-mounted tissue sections with characteristics indicating the labelling of a H1-histamine receptor. It is saturable (Bmax 12 pg/g tissue), of a high affinity (KD 0.5 mM) and possesses a drug specificity similar to that observed for H1 receptors in a variety of systems. In agreement with other biochemical studies, the association constant and the number of binding sites appear lower in the rat than in the guinea pig. Once the optimal conditions for labelling the receptors were found in the biochemical studies, tissue sections were prepared for autoradiographic studies. The receptor density varied markedly in the different brain regions. For example, there was a high density of H1 receptors in the molecular layer of the guinea pig cerebellum. In the guinea pig hippocampal formation, the highest densities were found in the molecular layer of the dentate gyrus while lower levels were found in the dendritic fields of the pyramidal cells. Significant densities of receptors were found in other areas of the rat and guinea pig brain as well.

The possible role of brain histamine and H1 and H2 receptors in the development of morphine tolerance and physical dependence in mice

The possible role of brain histamine in the mechanisms of morphine tolerance and physical dependence is under investigation in mice. L-histidine and histamine, given during the 'withdrawal' phase, significantly increase tolerance to the analgesic effects of morphine but reduce the degree of physical dependence. Metiamide significantly inhibits tolerance but has no consistent effect on physical dependence. These results suggest that H2 receptors may be involved in the development of morphine tolerance. Mepyramine does not significantly affect tolerance, and with regard to dependence there is an effect only on body weight loss, which is increased. However, combined treatment with metiamide and mepyramine inhibits tolerance significantly more than metiamide alone; and withdrawal jumping is also reduced more significantly by combined treatment than by the separate administration of these drugs. It is suggested that brain histamine is definitely implicated in the mechanisms of the 'withdrawal' phase of morphine tolerance and physical dependence in mice, with H2 receptors probably playing the more important part.

5-Hydroxytryptamine and histamine as mediators of the vascular injury produced by agents which damage mast cells in rats

Each of the four agents, ovomucoid, dextran, 48/80, and testis extract, when injected beneath the skin of the dorsa of the paws of rats produces a local vascular injury characterized by a protein-rich edema. Each agent also produces damage to mast cells. Either 5-hydroxytryptamine or histamine produces a response similar in the gross to that elicited by the agents which damage mast cells; however, neither of these two agents produces mast cell damage. On a weight basis 5-hydroxytryptamine is a much more potent edema-producing agent than histamine. The edema-producing action of 5-hydroxytryptamine can be differentiated from the similar action of histamine by the use of specific antagonists; dibenamine is a 5-hydroxytryptamine antagonist and pyrilamine a histamine antagonist. The edema produced by the mast cell-damaging agents is partially inhibited by dibenamine but is not diminished by pyrilamine. It is completely inhibited by treatment of rats with both drugs. The drugs which inhibit edema do not prevent mast cell damage by ovomucoid, dextran, 48/80, or testis extract. The observations are consistent with the hypothesis that agents which damage mast cells, "release" both 5-hydroxytryptamine and histamine and that in the rat the edema associated with mast cell damage is mediated largely by 5-hydroxytryptamine.