Articles: histamine.
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Chemical activation and sensitization of trigeminal primary afferent neurons innervating the intracranial meninges have been postulated as possible causes of certain headaches. This sensitization, however, cannot explain the extracranial hypersensitivity that often accompanies headache. The goal of this study was to test the hypothesis that chemical activation and sensitization of meningeal sensory neurons can lead to activation and sensitization of central trigeminal neurons that receive convergent input from the dura and skin. ⋯ Antidromic activation (current of <30 muA) of dura-sensitive neurons revealed projections to the hypothalamus, thalamus, and midbrain. These findings suggest that chemical activation and sensitization of dura-sensitive peripheral nociceptors could lead to enhanced responses in central neurons and that this central sensitization therefore could result in extracranial tenderness (mechanical and thermal allodynia) in the absence of extracranial pathology. The projection targets of these neurons suggest a possible role in mediating the autonomic, endocrine, and affective symptoms that accompany headaches.
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Nephron. Physiology · Jan 1998
Clinical TrialHistamine and serotonin in uremic pruritus: effect of ondansetron in CAPD-pruritic patients.
Pruritus is a common, unpleasant symptom of uremic patients. Serotonin and histamine have been reported as possible mediators ofuremic pruritus, and ondansetron is a potent and selective inhibitor of 5-HT3 receptors. The aims of our study were (1) to evaluate the effect of ondansetron on uremic pruritus in continuous ambulatory peritoneal dialysis (CAPD) patients and its safety and (2) to investigate the role of histamine and serotonin in uremic pruritus. ⋯ Three patients reported an improvement in their nausea and vomiting during the treatment. Weekly clinical and laboratory examinations showed no side effects, adverse reactions, or other complications. Our data indicate that ondansetron is an effective, safe, and well-tolerated drug for the treatment of uremic pruritus in CAPD patients and that histamine and serotonin may have a crucial role in the appearance or perception of the uremic pruritus.
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Scombroid fish poisoning is a food-borne chemical intoxication caused by certain spoiled fish that contain a large amount of histamine and some biogenic diamines. It has gradually become a world-wide medical problem and probably is the most common cause of fish poisoning. As the data on the incidents of scombroid fish poisoning in Taiwan remains scarce, we report 2 incidents of scombroid fish poisoning in Northern Taiwan. ⋯ The nonspecific but characteristic symptomatology of histamine food poisoning and previous consumption of fish should alert physicians to the possibility of scombroid fish poisoning. Unless complicated with shock or respiratory distress, supportive treatment with antihistamines usually concludes with a good prognosis. Toxin analysis of the fish flesh remains the most important step in approaching a confirmed diagnosis.
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To investigate the spinal processing of cutaneous pruritic and algesic stimuli, single-unit recordings were made from wide-dynamic-range-type lumbar spinal dorsal horn neurons in pentobarbital-sodium-anesthetized rats. Neuronal responses were recorded to mechanical and noxious thermal stimuli, as well as to microinjection (1 microl) of histamine (0.01-10% = 9 x 10(-1)-9 x 10(-4) M), capsaicin (0.1% = 3.3 x 10(-3) M), or other algesic chemicals into skin within the receptive field via intracutaneously placed needles. Most (84%) of the 89 neurons responded to intracutaneous (i.c.) microinjection of histamine with a brief phasic discharge followed by an afterdischarge of variable (s to min) duration. ⋯ The mean response to 80% ethanol was significantly smaller than to 0.1% capsaicin. All units tested also responded to topical application of mustard oil (50%) and i.c. serotonin (30 microg). The results are discussed in terms of theories that attempt to reconcile psychophysical and clinical observations of pain and itch sensation.
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Review
Hypothalamic neuronal histamine: implications of its homeostatic control of energy metabolism.
In a series of studies on histaminergic functions in the hypothalamus, probes to manipulate activities of histaminergic neuron systems were applied to assess its physiologic and pathophysiologic implications using non-obese normal and Zucker obese rats, an animal model of genetic obesity. Food intake is suppressed by either activation of H1-receptor or inhibition of the H3-receptor in the ventromedial hypothalamus (VMH) or the paraventricular nucleus, each of which is involved in satiety regulation. Histamine neurons in the mesencephalic trigeminal sensory nucleus modulate masticatory functions, particularly eating speed through the mesencephalic trigeminal motor nucleus, and activation of the histamine neurons in the VMH suppress intake volume of feeding at meals. ⋯ Abnormalities produced by depletion of neuronal histamine from the hypothalamus in normal rats mimic those of obese Zuckers. Grafting the lean Zucker fetal hypothalamus into the obese Zucker pups attenuates those abnormalities. These findings indicate that histamine nerve systems in the brain play a crucial role in maintaining homeostatic energy balance.