Spinal α-motoneurons directly innervate skeletal muscles and function as the final common path for movement and behavior. The processes that determine the excitability of motoneurons are critical for the execution of motor behavior. In fact, it has been noted that spinal motoneurons receive various neuromodulatory inputs, especially monoaminergic one. However, the roles of histamine and hypothalamic histaminergic innervation on spinal motoneurons and the underlying ionic mechanisms are still largely unknown. In the present study, by using the method of intracellular recording on rat spinal slices, we found that activation of either H or H receptor potentiated repetitive firing behavior and increased the excitability of spinal α-motoneurons. Both of blockage of K channels and activation of Na-Ca exchangers were involved in the H receptor-mediated excitation on spinal motoneurons, whereas the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels were responsible for the H receptor-mediated excitation. The results suggest that, through switching functional status of ion channels and exchangers coupled to histamine receptors, histamine effectively biases the excitability of the spinal α-motoneurons. In this way, the hypothalamospinal histaminergic innervation may directly modulate final motor outputs and actively regulate spinal motor reflexes and motor execution.
Animals ; Histamine ; pharmacology ; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ; metabolism ; Motor Neurons ; drug effects ; physiology ; Rats ; Receptors, Histamine H2 ; metabolism ; Sodium-Calcium Exchanger ; metabolism

OBJECTIVETo investigate the effects of histamine on the neurotoxicity induced by beta-amyloid(1-42)(Abeta42) in rat phaeochromocytoma (PC12) cells.

METHODSThe in vitro model of Alzheimer's disease was constructed with A beta42-treated PC12 cells. Cell morphology and MTT assay were used to evaluate the cell toxicity and histamine effects. The different histamine antagonists were applied to investigate the involvement of receptor subtypes.

RESULTThe neurotoxicity was induced by A beta42 in a concentration-dependent manner, which was reversed by histamine at concentration of 10(-7), 10(-6) mol/L. The effect was reversed by H(2) antagonist zolantidine and H(3)antagonist clobenpropit, but not by H(1) antagonist diphenhydramine.

CONCLUSIONHistamine reduces neurotoxicity induced by beta-amyloid(1-42), which may be mediated by H(2) and H(3)receptors.

Alzheimer Disease ; chemically induced ; metabolism ; prevention & control ; Amyloid beta-Peptides ; toxicity ; Animals ; Benzothiazoles ; pharmacology ; Diphenhydramine ; pharmacology ; Dose-Response Relationship, Drug ; Histamine ; pharmacology ; Histamine H2 Antagonists ; pharmacology ; Histamine H3 Antagonists ; pharmacology ; Imidazoles ; pharmacology ; Neuroprotective Agents ; metabolism ; pharmacology ; PC12 Cells ; Phenoxypropanolamines ; pharmacology ; Piperidines ; pharmacology ; Rats ; Receptors, Histamine H2 ; metabolism ; Receptors, Histamine H3 ; metabolism ; Thiourea ; analogs & derivatives ; pharmacology

OBJECTIVETo investigate histamine-induced changes of the intracortical vessels in the cortical slice of rat brain.

METHODSImmunohistochemistry was employed to detect the expression of H1 and H2 receptors in the intracortical blood vessels of rats. Histamine-induced constriction of the intracortical blood vessels of the brain slices was observed with differential interference contrast microscope. Measurements of the luminal diameter were made on-line during the course of the experiment and confirmed off-line from the stored images. In order to observe whether histamine H1 and H2 receptors affected histamine-induced constriction, the intracortical blood vessels in the brain slices were pre-treated with H1 receptor antagonist diphenhydramine and H2 receptor antagonist cimetidine.

RESULTSExpression of H1 and H2 receptors was detected in the intracortical blood vessels of the rat brain. Histamine (1-100 micromol/L) induced a concentration-dependent constriction from (1.48-/+0.67)% to (32.91-/+7.91)%. The reactions to each histamine concentration were significantly (P<0.01) different from each other, with the exception of the highest histamine concentrations (30 and 100 micromol/L) when maximal constriction due to histamine were observed (P>0.05). With pre-treatment of the slice with 10 micromol/L diphenhydramine, application of histamine did not elicit constriction. Pre-treatment of the slice with 10 micromol/L cimetidine did not completely inhibit but somehow significantly weakened vascular constriction in response to histamine treatment at 10 and 30 micromol/L (P<0.05).

CONCLUSIONHistamine can induce constriction of the intracortical blood vessels, which is mediated by H1 receptor.

Animals ; Blood Vessels ; drug effects ; metabolism ; physiology ; Cerebral Cortex ; blood supply ; Cimetidine ; pharmacology ; Diphenhydramine ; pharmacology ; Histamine ; pharmacology ; Histamine H1 Antagonists ; pharmacology ; Histamine H2 Antagonists ; pharmacology ; In Vitro Techniques ; Male ; Rats ; Rats, Sprague-Dawley ; Receptors, Histamine H1 ; metabolism ; physiology ; Receptors, Histamine H2 ; metabolism ; physiology ; Vasoconstriction ; drug effects

The ventral pallidum (VP) is a crucial component of the limbic loop of the basal ganglia and participates in the regulation of reward, motivation, and emotion. Although the VP receives afferent inputs from the central histaminergic system, little is known about the effect of histamine on the VP and the underlying receptor mechanism. Here, we showed that histamine, a hypothalamic-derived neuromodulator, directly depolarized and excited the GABAergic VP neurons which comprise a major cell type in the VP and are responsible for encoding cues of incentive salience and reward hedonics. Both postsynaptic histamine H1 and H2 receptors were found to be expressed in the GABAergic VP neurons and co-mediate the excitatory effect of histamine. These results suggested that the central histaminergic system may actively participate in VP-mediated motivational and emotional behaviors via direct modulation of the GABAergic VP neurons. Our findings also have implications for the role of histamine and the central histaminergic system in psychiatric disorders.
Action Potentials ; drug effects ; Animals ; Basal Forebrain ; cytology ; Dimaprit ; pharmacology ; Dose-Response Relationship, Drug ; Electric Stimulation ; Female ; GABAergic Neurons ; drug effects ; Histamine ; pharmacology ; Histamine Agonists ; pharmacology ; Lysine ; analogs & derivatives ; metabolism ; Male ; Patch-Clamp Techniques ; Pyridines ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, Histamine H1 ; metabolism ; Receptors, Histamine H2 ; metabolism ; Sodium Channel Blockers ; pharmacology ; Tetrodotoxin ; pharmacology ; gamma-Aminobutyric Acid ; metabolism

Endoscopic mucosal resection (EMR) results in the formation of iatrogenic gastric ulcers and the optimal treatments for such ulcers are still unclear. We aimed to evaluate the efficacy of rebamipide in the management of EMR-induced ulcers by comparing it with an H2 receptor antagonist. After EMR, patients were randomly assigned into either rebamipide or famotidine groups. All patients received a one-week lansoprazole 30 mg q.d. therapy followed by three-week famotidine (20 mg b.i.d.) or rebamipide (100 mg t.i.d.) therapy. Four weeks after the treatments, ulcer sizes, stages, bleeding rates, and ulcer-related symptoms were compared using endoscopy and a questionnaire. A total of 63 patients were enrolled in this study. Finally, 51 patients were analyzed, 26 in rebamipide and 25 in famotidine group. Baseline characteristics were not significantly different between the two groups. Four weeks after EMR, the two groups were comparable in terms of ulcer reduction ratio (P=0.297), and ulcer stage (P=1.000). Moreover, no difference was observed with regard to ulcer-related symptoms, drug compliance, adverse drug event rates, and bleeding rates. Our data suggest that rebamipide is not inferior to famotidine in healing iatrogenic gastric ulcers, and could be a therapeutic option in the treatment of such ulcers.
Adult ; Aged ; Aged, 80 and over ; Alanine/*analogs & derivatives/therapeutic use ; Anti-Ulcer Agents/*therapeutic use ; Endoscopy, Gastrointestinal/*adverse effects ; Famotidine/*therapeutic use ; Histamine H2 Antagonists/*therapeutic use ; Humans ; Iatrogenic Disease ; Male ; Middle Aged ; Pilot Projects ; Prospective Studies ; Quinolones/*therapeutic use ; Receptors, Histamine H2/metabolism ; Stomach Ulcer/*drug therapy/*etiology/pathology ; Wound Healing