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Ca2+/calmodulin system: participation in the progesterone-induced facilitation of lordosis behavior in the ovariectomized estrogen-primed rat.

We studied the effect some drugs that participate in the Ca2+/ calmodulin system have on the progesterone (P) facilitation of lordosis behavior in ovariectomized estradiol (E2) primed rats. We injected rats 44 h after E2 priming with 2 mg P together with various dosages of one of the following compounds: pentobarbital, trifluoperazine (TPZ), promethazine (PMZ), Chlorpromazine (CPZ), haloperidol (HAL), pimozide (PIM), and verapamil (VER). Then 4 h after treatment, animals were tested for sexual behavior, expressed as the lordosis quotient (LQ). All drugs at 4 mg/kg or higher inhibited lordosis, but only HAL, PIM, and VER were active at 1 mg/kg. The maximum level of activity was shown by PIM, although at the dose of 8 mg/kg no statistical differences were found between this compound and TPZ or HAL. Pentobarbital (25 mg/kg) showed no significant difference from saline-treated controls. The activity of the tested drugs on the facilitation of sexual behavior appears to be related to their efficiency as inhibitors of calmodulin (CaM)-dependent phosphodiesterase and as ligands for the Ca(2+)-CaM complex.

Animals↗

Skin test suppression by antihistamines and the development of subsensitivity.

The suppression of skin test reactivity by single doses of six antihistamines was measured before and after a period of daily antihistamine ingestion in 18 subjects. Single doses of hydroxyzine, 50 mg; chlorpheniramine, 16 mg; and promethazine, 50 mg; induced significant suppression of skin test reactivity at 2 hr, whereas the suppression produced by tripelennamine, 100 mg; diphenhydramine, 50 mg; and cyproheptadine, 16 mg; did not differ significantly from that produced by placebo. After 3 wk of treatment with hydroxyzine, 75 mg per day, the suppressive effect of hydroxyzine as well as the five clinically unrelated antihistamines was significantly reduced. Although the response to chlorpheniramine was also reduced after chronic treatment with chlorpheniramine, 24 mg per day, the difference was not statistically significant. We conclude that antihistamines in the doses used differ greatly in their suppressive effect on skin test reactivity. The antihistamine producing the most skin test suppression, hydroxyzine, when it was taken daily for 3 wk, caused the development of partial tolerance not only to its own effect but to those of clinically unrelated antihistamines.

Adolescent↗

Space motion sickness.

Space motion sickness, presumably triggered by sudden entry into a weightless environment, occurred with unexpected frequency and severity among astronauts who flew the Skylab missions. Recovery from symptoms was complete within 3-5 days, and as revealed by the Skylab M131 Human Vestibular Function Experiment, all crewmembers were immune to experimentally induced motion sickness after mission day 8. This syndrome has been recognized as a possible threat to the early mission well-being and operational efficiency of at least some individuals who will fly space missions in the future. The causes of space motion sickness are not clearly understood, nor have satisfactory methods been identified to date for its prediction, prevention and treatment. In order to minimize the potential impact of this syndrome on Space Shuttle crew operations the National Aeronautics and Space Administration has organized a broad program of inter-disciplinary research involving a large number of scientists in the United States. Current research on the etiology of space motion sickness is based to a large extent on the so called sensory conflict theory. Investigations of the behavioral and neurophysiological consequences of intralabyrinthine, as well as intermodality sensory conflict are being performed. The work in this area is being influenced by the presumed alterations that occur in otolith behavior in weightlessness. In addition to sensory conflict, the possible relationship between observed cephalad shifts of body fluids in weightlessness and space motion sickness is being investigated. Research to date has failed to support the fluid shift theory. Research underway to identify reliable test methods for the prediction of susceptibility to space motion sickness on an individual basis includes attempts to (a) correlate susceptibility in different provocative environments; (b) correlate susceptibility with vestibular and non-vestibular response parameters, the latter including behavioral, hemodynamic and biochemical factors and (c) correlate susceptibility with rate of acquisition and length of retention of sensory adaptation. Controlled studies are also being performed during parabolic flight as a means of attempting to validate predictive tests for susceptibility to this syndrome. Research to develop new or improved countermeasures for space motion sickness is underway in two primary areas. One of these involves anti-motion sickness drugs. Significant achievements have been realized with regard to the identification of new highly efficacious drug combinations, dose levels and routes of administration. Although pronounced individual variations must be accounted for in selecting the optimum drug and dose level, combinations of promethazine plus ephedrine or scopolamine plus dexidrine are presently the drugs of choice. Work is also underway to identify side effects associated with anti-motion sickness drug use and to identify new drugs which may selectively modify activity in central neural pathways involved in motion sickness. In addition to research on drugs, efforts are being made to develop practical vestibular training methods. Variables which influence rate of acquisition of adaptation, length of retention of adaptation and transfer of protective adaptation to new environments are being evaluated. Also, included in this area is the use of biofeedback and autogenic therapy to train individuals to regulate autonomic responses associated with motion sickness. While valuable new knowledge is expected to evolve from these combined research programs, it is concluded that the final validation of predictive tests and countermeasures will require a series of controlled space flight experiments.

Adaptation, Physiological↗

Ultrastructural study of the response of eosinophil granule cells to Aeromonas salmonicida extracellular products and histamine liberators in rainbow trout Salmo gairdneri Richardson.

Intraperitoneal injections of Aeromonas salmonicida extracellular products (ECP), Compound 48/80 and Concanavalin A were found to degranulate the eosinophil granule cells (EGC) in the lower intestine and rectum of the rainbow trout Salmo gairdneri Richardson. Ultrastructurally, the EGC response resembled the anaphylactic granule extrusion of mammalian mast cells. Varying degrees of granule vacuolation and loss of electron density occurred. Labyrinthine channels were observed at the peak of degranulation. EGC response however, differed from mammalian mast cells in two respects. Firstly, degranulation involved the release of intact electron lucent granules and the subsequent disintegration of the granule matrix extracellularly. Mammalian mast cells on the other hand, release their granules by direct exocytosis. Secondly, the 48/80 and Con A-stimulated EGC degranulation was inhibited by antihistamines, promethazine and cimetidine. In mast cells, antihistamines do not prevent granule release but block histamine receptors in target cells. The degranulation of the ECGs was a non-cytotoxic event and the cells were capable of regeneration. As soon as the cells lost most of their granules, increased cytoplasmic activity was observed. This involved the expansion of the Golgi-endoplasmic reticulum complex.

Aeromonas↗

Anaphylaxis to muscle relaxant drugs: cross-reactivity and molecular basis of binding of IgE antibodies detected by radioimmunoassay.

IgE antibodies that bind the muscle relaxant alcuronium were found in sera from six patients who experienced anaphylactic-like reactions following administration of the drug during induction of anaesthesia. Drug-specific antibodies were detected by radioimmunoassay employing a covalently coupled alcuronium-Sepharose complex and 125I-labelled anti-human IgE. Quantitative inhibition studies undertaken with the sera revealed specificity differences between IgE antibodies from different patients. One serum reacted with alcuronium but not with five other muscle relaxants, decamethonium, gallamine, pancuronium, succinylcholine and tubocurarine. IgE antibodies in the other sera cross-reacted with the muscle relaxants, other quaternary ammonium compounds and some pharmacologically unrelated drugs including promethazine, morphine, neostigmine and pentolineum. The inhibition experiments revealed that the alcuronium-IgE reaction could be prevented or diminished by structures containing a substituted ammonium ion. As these ions occur widely in man's environment in drugs, cosmetics, disinfectants, foods and industrial materials, it seems possible that sensitization of patients may occur without previous exposure to muscle relaxants.

Adult↗

Photopatch testing: the 5-year experience of the German, Austrian, and Swiss Photopatch Test Group.

A cooperative photopatch test study was conducted by 45 dermatologic centers in Austria, Germany, and Switzerland. Results obtained from 1985 to 1990 are presented. A standard photopatch test tray of 32 substances was applied to the back of patients with suspected photosensivity. After applications for 24 hours, test sites were irradiated with 10 joules/cm2UVA. Unirradiated controls were included. Readings were performed immediately and 24, 48, and 72 hours after irradiation; responses were qualitatively graded on a 4-point scale. All data were stored and processed by a computer. With computer-assisted analysis of reaction patterns photoallergic reactions were identified and distinguished from phototoxic reactions. Data of 1129 patients were evaluated. Among a total of 2859 positive test reactions in 870 patients, 2041 in 778 patients were found to be photoinduced and 818 in 413 patients were contact reactions; 108 reactions in 83 patients were classified as photoallergic. Nonsteroidal anti-inflammatory drugs, disinfectants, sunscreens, phenothiazines, and fragrances caused most often photoallergic reactions. Many unspecific phototoxic reactions were induced by tiaprofenic acid, promethazine, carprofen, chlorpromazine, fenticolar, wood balsam of Peru, and perfumes. Despite the distinction between photoallergic and phototoxic responses, many test reactions lacked relevance for the patients' dermatoses.

Adolescent↗

A comparison of the effects of chlorpromazine and more selective histamine and 5-hydroxytryptamine antagonists on human IgG synthesis in vitro.

We have shown previously that chlorpromazine, a drug associated with immunological abnormalities in vivo, significantly potentiates pokeweed mitogen (PWM)-stimulated IgG synthesis by human peripheral blood mononuclear cells (PBMC) in culture. Chlorpromazine is a pharmacological antagonist of histamine and 5-hydroxytryptamine (5-HT) and thus may exert its immune-enhancing effects by competing with these amines for their respective receptors, which are known to be present on lymphocytes. In this report we show that histamine and 5-HT are present at micromolar concentrations in PBMC cultures. To examine the role of histamine and 5-HT in chlorpromazine-induced enhancement of IgG synthesis we incubated PWM-treated cells with a range of selective histamine and 5-HT antagonists, and with the amines added to cultures either alone or in combination with chlorpromazine. The H1 antagonists mepyramine and promethazine and the H2 antagonist cimetidine had no significant effect on IgG synthesis. The combined 5-HT1/5-HT2 antagonists methysergide and methiothepin also failed to modulate synthesis. Neither histamine nor 5-HT at concentrations up to 100 microM modulated IgG synthesis, nor did they abrogate the enhancement of IgG synthesis induced by chlorpromazine. We conclude that the modulation of IgG synthesis in vitro by chlorpromazine cannot be attributed to an interaction of this drug with lymphocyte receptors for histamine and 5-HT. Other possibilities for the mechanism of action of this drug on immune function are discussed.

Cells, Cultured↗

Pro-inflammatory flavonoids which are inhibitors of prostaglandin biosynthesis.

Catechin dimers induce a large long-lasting oedema when injected in the paw of the rat. This oedema is not inhibited by methysergide, promethazine, indomethacin, phenidone, bromophenacyl bromide and colchicine. It is not modified in rats made leukopenic by methotrexate. It is slightly delayed in Brown Norway rats which were kallikrein-kininogen deficient. Similarly catechin dimers induce the formation of a large peritoneal exudate in the rat. The exudate contains insignificant levels of leucocytes and 5-hydroxytryptamine. It contains kinins but its PG content is very low. The exudate does not activate (14C)-arachidonic acid into PG. Catechin dimers induce kinin formation in rat plasma "in vitro". They inhibit the formation of PG and HETE-like compounds from (14C)-arachidonic acid by rat peritoneal cells "in vitro". Catechin dimers administered at sub-irritant doses reduced carrageenan-induced oedema. Catechin dimers at low doses have an anti-inflammatory effect which may depend on PG synthesis inhibition. At larger doses, they induce inflammatory responses which occur with almost complete lack of participation of PG.

Animals↗

Susceptibilities of drugs to nitrosation under standardized chemical conditions.

Of 22 drugs with either a N,N-dimethylamino, N,N-diethylamino or N-morpholino group in the molecule, eight were converted to volatile N-nitrosamines by nitrosative cleavage in reactions of nitrite and drug in a molar ratio of 4:1 at pH 3. Under standardized conditions yields were greatest with aminopyrine and minocycline which contains two N,N-dimethylamino groups in the molecule. Oxytetracycline, chlortetracycline, tetracycline, promethazine, chlorpromazine, imipramine and disulfiram gave much lower yields and amitriptyline, clomiphene, clomipramine, dextropropoxyphene, diphenhydramine, disopyramide, erythromycin, mepyramine, methapyrilene, penicillin G procaine salt, procaine, tamoxifen, trimeprazine and tripelennamine yielded no detectable levels of volatile N-nitrosamines. Nitrosation products of 57 drugs were also examined by a group selective procedure estimating both volatile and non-volatile N-nitroso compounds. Virtually all of the yield obtained from aminopyrine or minocycline could be accounted for by N-nitrosodimethylamine (NDMA). However, compounds yielding excess N-nitrosamines compared to NDMA were obtained from the other three tetracyclines, presumably as a result of the cleavage of a methyl group from the N,N-dimethylamino substituent to form desmethyl-N-nitroso compounds. In general, the drugs giving the highest yields of N-nitroso compounds were those containing secondary rather than tertiary amino groups. A considerable range of susceptibilities towards nitrous acid was observed overall; ten drugs containing a secondary or tertiary amino- or amido- or hydrazido - group did not react with nitrous acid to form N-nitroso compounds.

Chemical Phenomena↗

Histamine (H2) receptor-adenylate cyclase system in pig skin (epidermis).

Histamine activated adenylate cyclase in pig skin (epidermal) slices, resulting in the accumulation of cyclic AMP. This effect was highly potentiated by the addition of cyclic AMP-phosphodiesterase inhibitors (theophylline, papaverine). A specific H2 receptor inhibitor (metiamide) inhibited the effect of histamine completely, while other antihistamines (diphenhydramine, acetophenazine, perphenazine, fluphenazine, promethazine) inhibited the effect of histamine to various lesser degrees. It has been shown that both epinephrine and prostaglandin E stimulate epidermal adenylate cyclase. Our data using specific blocking agents indicate that histamine, epinephrine and prostaglandin E2 act independently on the epidermal adenylate cyclase system.

Adenylyl Cyclases↗

Guanidines as analogs of histamine and antihistamines on the isolated guinea-pig ileum.

The present work describes the interaction of phenylguanidine and cyclohexylguanidine with receptor structures of the isolated guinea-pig ileum. It is suggested that phenylguanidine in the range of 0.2-2 mM, acts in a way similar to histamine. At lower concentrations in the bath, phenylguanidine and cyclohexylguanidine, behave as competitive antagonists of histamine, with Ki values close to 0.1 mM and 0.4 mM, respectively. At higher concentrations phenylguanidine acts as agonist with a Kn near 0.3 mM; the Kn for histamine was found to be 0.127 muM, in agreement with previous data from the literature. The agonistic action of phenylguanidine is inhibited by promethazine and atropine, which have Ki values of 0.342 muM and 0.575 muM, respectively. Cyclohexylguanidine is devoid of spasmogenic activity, and this was attributed to the lack of aromatic character and to the bulkiness of the cyclohexyl side chain.

Animals↗

Phenothiazines are potent inhibitors of osteoclastic bone resorption.

1. We have previously shown that promethazine inhibits osteoclastic bone resorption in the in vitro bone slice assay (IC50 = 0.8 microM), but the mechanism(s) involved are unclear. 2. We have now tested the effects on osteoclast activity of five other structurally related compounds. Phenothiazine, chlorpromazine, amitriptyline, phenazine, and phenoxazine had IC50 values of 0.8, 0.9, 6, 7, and > 10 microM, respectively, in the bone slice assay, indicating that the basic phenothiazine structural element itself is important for osteoclast inhibitory activity. 3. The results are discussed in terms of the known effects of phenothiazines on plasma membrane fluidity, blocking of ion channels, and inhibition of calmodulin.

Animals↗

Evidence for excitatory actions of histamine on supraoptic neurons in vitro: mediation by an H1-type receptor.

The effects of histamine on the firing of supraoptic neurosecretory neurons in the rat were examined in vitro using acutely prepared, hypothalamo-neurohypophysial explants perifused with an artificial cerebrospinal fluid. Extracellular action potentials meeting the criteria of antidromic invasion from neurohypophysial stalk stimulation were recorded from 135 neurons in the tuberal portion of the supraoptic nucleus, which lies superficially along the tuber cinereum and consists of mostly vasopressin-containing neurons. Units could be classified as slow/silent (76.3%), phasic (21.5%) or continuous (2.2%) on the basis of their spontaneous activity. Histamine applied briefly to the perifusate excited approximately one-third of the slow silent neurons and approximately two-thirds of the phasic neurons, with a wide range (10(-3)-10(-9)) in the effective concentration across neurons. The H1-receptor agonists 2-pyridylethylamine and 2-thiazolylethylamine mimicked these excitations in 10 of 12 and 3 of 6 neurons tested, respectively. The H2-receptor agonists dimaprit (4 neurons) and impromidine (5 neurons) failed to excite any of the tested neurons previously excited by histamine. The H1-receptor antagonist promethazine antagonized histamine's excitatory effect in 8 of 9 cells, while the H2-receptor antagonist cimetidine had little effect on the 9 cells tested. Histamine also modified bursts of activity induced in some slow/silent neurons by antidromic stimulation without having an observable effect in the absence of an antidromic burst. In 10 of 18 neurons histamine produced an elongation of burst duration and a modest increase in intraburst firing rate when applied during an antidromically evoked burst. In an additional 5 of 17 neurons, which had neither previously responded to histamine nor shown an antidromically-evoked burst, the pairing of histamine application and antidromic shocks resulted in an antidromically evoked burst. The effects of histamine on evoked bursts also appeared to be mediated by an H1-receptor. Histamine's excitation of supraoptic neurons is thus dependent on the electrical activity expressed by the neuron at the time of testing. Conductances activated by depolarization of the neuron may be modified by histamine or this compound may alter the threshold for burst generation. Considered with data showing H1-receptor localization and histamine-immunoreactive fibers within the supraoptic nucleus, the present results, as well as those showing the potency of centrally applied histamine in releasing vasopressin, suggest histamine may act physiologically by altering the electrical activity of vasopressin-secreting neurons.

Action Potentials↗

Histamine enhances the depolarizing afterpotential of immunohistochemically identified vasopressin neurons in the rat supraoptic nucleus via H1-receptor activation.

Previous studies have demonstrated that histamine primarily excites unidentified neurons in the rat supraoptic nucleus. We investigated the neuromodulatory effects of histamine on immunohistochemically identified vasopressin neurons in the rat supraoptic nucleus using intracellular recording techniques from the hypothalamo-neurohypophysial explant. Exogenous application of histamine (0.1-100 microM) to vasopressinergic neurons produced a small membrane depolarization accompanied by an increase of up to 100% in the amplitude of the depolarizing afterpotential that follows current-evoked trains of action potentials. The enhancement of the depolarizing afterpotential by histamine did not depend upon the depolarization. Further, histamine enhanced the amplitude of the depolarizing afterpotential when blocking the afterhyperpolarizing potential with d-tubocurarine or apamin, and in the presence of tetrodotoxin and d-tubocurarine or apamin, indicating a postsynaptic action of histamine on the depolarizing afterpotential that is not simply a reflection of a decrease in the afterhyperpolarizing potential. These toxins also had no effect on the histamine-induced depolarization. The enhancement of the depolarizing afterpotential by histamine was mimicked by the histamine H1-receptor agonist 2-thiazolylethylamine and was reduced or blocked by the H1-receptor antagonist promethazine, but was not blocked or reduced in the presence of the histamine H2-receptor antagonist, cimetidine. In summary, these results show that the excitatory effect of histamine on immunohistochemically identified vasopressin neurons in the supraoptic nucleus is due in part to the H1-receptor-mediated enhancement of the depolarizing afterpotential independent of any change in the afterhyperpolarizing potential or membrane potential.

Animals↗

Histamine-induced prolonged depolarization in rat supraoptic neurons: G-protein-mediated, Ca(2+)-independent suppression of K+ leakage conductance.

Ionic mechanisms responsible for histamine-induced prolonged depolarization in supraoptic nucleus neurons were investigated using whole-cell patch recordings in horizontally prepared brain slices from adult male rats. Bath application of histamine (1-10 microM) in control medium induced membrane depolarization in nine of 12 phasically firing, putative vasopressin cells, but not in continuous firing, putative oxytocin cells (none of five cells). Depolarization, usually accompanied by increased firing rate, started within 20 s after histamine reached the slices, lasting for 3-13 min, after which they repolarized, and this was repeatable upon washout. Chelation of intracellular Ca2+ with 11 mM 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetate and perfusion of slices with Ca(2+)-free medium blocked neither histamine-induced membrane depolarizations nor increased firing rates in 24 of 30 cells recorded. Depolarizations were always associated with decreases in membrane conductance. Following treatment with promethazine (H1 receptor antagonist) in six cells excited previously by histamine, subsequent application induced neither membrane depolarization nor increased firing. H1 receptor agonists mimicked histamine-induced depolarization (four of six cells) but the H2 receptor agonist, dimaprit (10 microM), had no effect (all of nine cells). In medium containing 0 mM Ca2+, 2 mM Co2+ and 1-2 microM tetrodotoxin, with internal Ca2+ chelation, bath application of histamine induced an apparent inward current in 15 of 20 supraoptic neurons tested. The peak of inward current evoked by 1-10 microM histamine at holding potentials around -50 mV varied from 10 to 50 pA (27.3 +/- 0.3 pA, mean +/- S.E.M.). Ramp voltage tests revealed that this inward current decreased as membrane potential was hyperpolarized and had a reversal potential of -90.1 +/- 3.8 mV (n = 10). Subtraction of current obtained before from that during histamine application revealed a current that was linear against membrane potential. Increasing external K+ concentration or introduction of K+ channel blockers in the medium attenuated or abolished histamine-induced inward current at membrane potentials close to -50 mV. When external Cl- concentration was reduced, histamine-induced inward current was still seen in five of seven supraoptic cells tested. Neither inward current nor change in conductance was observed following bath application of histamine in 11 of 12 neurons recorded using patch pipettes containing guanosine 5'-O-(2-thiodiphosphate), and in seven of eight neurons using pipettes containing guanosine 5'-O-(3-thiotriphosphate). These results suggest that histamine depolarizes supraoptic neurons, at least in part, by inhibiting a K+ leakage current mediated by H1 receptors linked to GTP-binding proteins and Ca(2+)-independent pathways. This study provides initial evidence for the second messengers regulating K+ leakage current.

Animals↗

Use of fetal mouse salivary glands in culture to detect embryotoxicity: evaluation of eight additional chemicals.

Several developmental processes interact to convert an epithelial bud into a gland with many lobes. For each chemical tested, 20 glands were placed into a control and each of 3 concentrations of the chemical. From dose-response curves, the concentration that reduced gland growth by 50% was determined and divided into the LD50 for mice. These ratios were used to compare the toxicity of the chemicals. The ratios of cyclamate, diphenhydramine, allopurinol, nitrofen and urethane would indicate that embryotoxicity would not be expected without maternal toxicity. Promethazine, diethyldithiocarbamate, and 5-fluorouracil would be expected to show embryotoxicity without maternal toxicity.

Animals↗

High-performance liquid chromatographic determination of terguride in solid dosage forms and plasma.

A simple and rapid HPLC method was developed to determine terguride in terguride hydrogenmaleate, coated tablets and plasma. The assay was carried out on a glass column of SGX CN (150 x 3.3 mm I.D.) using methanol and phosphate buffer solution (pH 7.0) as the mobile phase, with detection at 227 nm. Terguride was quantified using promethazine as an internal standard. The tablet matrix was extracted into methanol. Plasma samples were deproteinated with acetonitrile and the supernatant was injected into the HPLC system. The method is linear, quantitative and reproducible.

Animals↗

The analytical control of the composition of creams.

The analysis without prior sample clean-up of promethazine hydrochloride or clioquinol in commercially available creams has been investigated using UV-spectrophotometry and titrimetric methods. The results were compared with those obtained by GLC and HPLC. Although in some cases the active drug could be determined satisfactorily using the comparatively non-selective UV-absorbance or titrimetric methods, these methods were found to be reliable only when applied to creams for which the qualitative and quantitative composition was completely known. Without prior sample clean-up, these methods will therefore be of interest mainly for process control purposes in manufacturing.

Journal Article↗