Effects of histamine and related compounds on regional cerebral blood flow in rats.
The effects of histamine and related compounds on regional cerebral blood flow (rCBF) in the hippocampus of conscious rats were studied. Intracerebroventricular injection of histamine caused a dose-dependent increase in rCBF in the hippocampus, and similar findings were observed with not only the H1 agonist, 2-thiazolylethylamine, but also the H2 agonist, dimaprit. Intraperitoneal injection of L-histidine also resulted in an increase in rCBF in the hippocampus, in parallel with elevation of histamine content in the brain. The increase in rCBF in the hippocampus induced by L-histidine was antagonized by both H1 and H2 antagonists (diphenhydramine, pyrilamine and zolantidine). In addition, when both antagonists were injected simultaneously, an additive effect was observed in antagonism of the L-histidine-induced increase in rCBF. L-Histidine caused no marked changes in blood pressure even at a dose of 1,500 mg/kg, which showed an increase in rCBF in the hippocampus. These results indicate that histamine elicited an increase in rCBF via both H1 and H2 receptors.
Suzuki
G
G
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
Chen
Z
Z
Sugimoto
Y
Y
Fujii
Y
Y
Kamei
C
C
D000818:Animals; D052160:Benzothiazoles; D001794:Blood Pressure / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects*; D017259:Dimaprit / Q000494:pharmacology; D004155:Diphenhydramine / Q000494:pharmacology; D004347:Drug Interactions; D006624:Hippocampus / Q000098:blood supply*; D006632:Histamine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D017442:Histamine Agonists / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006635:Histamine H2 Antagonists / Q000494:pharmacology; D006639:Histidine / Q000494:pharmacology; D008297:Male; D050198:Phenoxypropanolamines; D010880:Piperidines / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000187:drug effects*; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors
D052160:Benzothiazoles; D017442:Histamine Agonists; D006633:Histamine Antagonists; D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D050198:Phenoxypropanolamines; D010880:Piperidines; D013844:Thiazoles; C029345:2-(2-aminoethyl)thiazole; D006639:Histidine; D006632:Histamine; D004155:Diphenhydramine; D011738:Pyrilamine; C055302:zolantidine; D017259:Dimaprit