title: Direct evidence for increased continuous histamine release in the striatum of conscious freely moving rats produced by middle cerebral artery occlusion.
abstract: Extracellular histamine in the stratum of conscious freely moving rats collected by intracerebral microdialysis 1 day after implantation of a U-shaped dialysis probe was measured by HPLC coupled with postcolumn o-phthalaldehyde derivatization fluorometry. The basal fractional histamine outputs were almost constant from 1 to 7 h after the start of perfusion (5.9-8.4 pg/30 min). Depolarization by perfusion with a high K+ (100 mM)-containing medium produced a significant (124%) increase and neuronal blockade by perfusion with a tetrodotoxin (1 microM)-containing medium resulted in a 68% reduction in the histamine output. The histamine output was markedly reduced by intraperitoneal injection of alpha-fluoromethylhistidine (100 mg/kg), an irreversible inhibitor of histidine decarboxylase, or (R)-alpha-methylhistamine (5 mg/kg), a potent and specific H3-receptor agonist. After middle cerebral artery (MCA) occlusion, the histamine output gradually increased, and reached four times the control value 8 h later. When rats were pretreated with metoprine (10 mg/kg), a histamine N-methyltransferase inhibitor, there was no significant difference in the histamine output between the MCA-occluded and the sham-operated groups during the first 3.5 h after the operation, but the histamine output gradually increased thereafter in the MCA-occluded group. In rats treated with alpha-fluoromethylhistidine, MCA occlusion failed to cause an increase in the histamine output. These results demonstrate that MCA occlusion induces a long-lasting increase in neuronal histamine release in the rat striatum.
authors.affiliation: Department of Pharmacology, Okayama University Medical School, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Adachi
authors.forename: Y
authors.initials: Y
authors.lastname: Itoh
authors.forename: R
authors.initials: R
authors.lastname: Oishi
authors.forename: K
authors.initials: K
authors.lastname: Saeki
mesh_terms: D000818:Animals; D001923:Brain Chemistry; D002545:Brain Ischemia / Q000150:complications / Q000378:metabolism*; D002544:Cerebral Infarction / Q000209:etiology; D003342:Corpus Striatum / Q000378:metabolism*; D004195:Disease Models, Animal; D006632:Histamine / Q000031:analogs & derivatives / Q000494:pharmacology; D006636:Histamine Release / Q000187:drug effects; D008297:Male; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D011189:Potassium Chloride; C054284:alpha-fluoromethylhistamine; D006632:Histamine