Effects of histamine H1-antagonists on sleep-awake state in rats placed on a grid suspended over water or on sawdust.
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The present study was performed to investigate the effects of histamine H(1)-antagonists on the sleep-awake state in rats placed on a grid suspended over water in comparison with rats placed on sawdust. When rats were placed on the grid suspended over water, significant increases in the awake time and decreases in non-rapid eye movement (non-REM) sleep time were observed compared with in rats on sawdust, even when measured hourly for 6 h. Diphenhydramine, chlorpheniramine and promethazine caused a significant decrease in the awake time and increase in non-REM sleep time in rats placed on the grid suspended over water for 1-2 h and/or 2-3 h after administration. On the other hand, in rats placed on sawdust, no significant differences were observed in the awake time and non-REM sleep time with diphenhydramine and chlorpheniramine compared with the control. Different from these two drugs, promethazine caused a significant decrease in the awake time and increase in non-REM sleep time 1-2 h and 2-3 h after administration even when rats were placed on sawdust at a relatively high dose. These results clearly indicate that histamine H(1)-antagonists had potent effects on decreasing the awake time and increasing non-REM sleep time under the conditions of an activated histaminergic system. (+info)
Effects of biogenic amines on the formation of adenosine 3', 5'-monophosphate in human thyroid slices.
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The effects of various concentrations of biogenic amines on the formation of adenosine-3', 5'-monophosphate (cyclic AMP) and their interactions with other thyroid stimulators were investigated in human thyroid slices from normal and Graves' disease. Most of biogenic amines were found to have the stimulatory effects to some extent. Among the biogenic amines tested, histamine was the most potent thyroid stimulator, norepinephrine and serotonin, the intermediate in terms of cyclic AMP formation. The effect of histamine was almost as potent as TSH in thyroid slices from Graves' disease. This stimulatory effect of histamine was blocked by metiamide, a histamine H2-receptor antagonist, but not by chlorpheniramine, a histamine H1-receptor antagonist. The effect of norepinephrine was completely inhibitied by propranolol, but not by phentolamine. Polyphloretin phosphate did not inhibit norepinephrine- or histamine-induced cyclic AMP formation, while it significantly depressed cyclic AMP formation induced by prostaglandin E2. The maximal effect of histamine was additive to that of TSH. It is suggested that biogenic amines, histamine and norepinephrine, in particular, have the thyroid receptors different from that of TSH or prostaglandin E2 and could play an important role in thyroid physiology. (+info)
Histamine H1 receptor blockade predominantly impairs sensory processes in human sensorimotor performance.
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Decreased H2 histamine response of granulocytes of asthmatic patients.
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Increased bronchial sensitivity to inhaled histamine in asthma is well known. The mechanism of this increased bronchial sensitivity is not known nor has it been demonstrated that isolated cells respond abnormally to histamine. Polymorpho-nuclear leukocytes (PMNs) provide a homogeneous cell population to study agonist response. Release of granulocyte lysosomal enzymes is inhibited by agonists increasing the PMN cyclic AMP concentration. The release of the lysosomal enzyme beta glucuronidase by serum-activated particles of zymosan was similar in PMNs isolated from normal and asthma subjects. Histamine (100-0.01 muM) inhibited enzyme release. Except at the maximal concentration of histamine (100 muM), the response to histamine was decreased in asthma. The inhibition of enzyme release paralleled an increase in intracellular PMN cyclic AMP. In asthma, the cyclic AMP response to histamine was reduced. The H2 antihistamine metiamide blocked histamine inhibition of lysosomal enzyme release and the increase in cyclic AMP. The effect was maximal at concentrations equimolar to those of histamine. The H1 antihistamine chlorpheniramine had no effect on histamine inhibition of granulocyte lysosomal enzyme release. A decrease in the inhibition of the release of the inflammatory lysosomal enzymes from granulocytes in asthma may contribute to an enhanced bronchial inflammatory reaction. (+info)
Chlorpheniramine impairs spatial choice learning in telencephalon-ablated fish.
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Preparation and evaluation of differently sulfonated styrene-divinylbenzene cross-linked copolymer cationic exchange resins as novel carriers for drug delivery.
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A study on CNS-side effects of mequitazine, an H1-specific antihistamine in healthy Thai volunteers.
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Mequitazine is a potent, non-sedative, long-acting H1-specific antihistamine proven to be a better therapeutic drug than other conventional antihistamines. It is also reported by many authors that the drug produces less sedative or other depressive actions on the central nervous system than other antihistamines. In order to evaluate the advantage of this drug in Asian people, an assessment of side effects of mequitazine, in comparison with chlorpheniramine, on the central nervous system was done in 20 healthy Thai volunteers, 10 males and 10 females 23-39 years of age, using a double blind crossover placebo controlled trial. Various subjective tests: alertness scale rating, visual analogue scale rating as well as objective tests: card sorting, glassbead picking and estimation of reaction time, were performed. There were no significant differences in side effects on the central nervous system between mequitazine and the placebo, whereas chlorpheniramine did produce side effects. (+info)