Effects of the histamine H3 receptor ligands thioperamide and (R)-alpha-methylhistamine on histidine decarboxylase activity of mouse brain.
The effects of the histamine H3 receptor ligands thioperamide and (R)-alpha-methylhistamine on the histidine decarboxylase (HDC) activity and histamine content of mouse brain were examined. Thioperamide, a histamine H3 antagonist, significantly increased the HDC activity in the brain of ddY, W/Wv and ICR mice 2-6 hr after its intraperitoneal (i.p.) injection. On the other hand, (R)-alpha-methylhistamine, a histamine H3-receptor agonist, caused no significant change in the HDC activity. The whole brain histamine content of ddY mice decreased significantly to 60-70% of the control level 2-8 hr after injection of thioperamide (25 mg/kg, i.p.), but then increased to 90% of the control level 10 hr after the injection. These in vivo results showed that blockade of the presynaptic histamine H3-receptor, which causes release of presynaptic histamine, increased the HDC activity.
Sakai
N
N
Department of Pharmacology I, Tohoku University School of Medicine, Sendai, Japan.
Sakurai
A
A
Sakurai
E
E
Yanai
K
K
Maeyama
K
K
Watanabe
T
T
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D006632:Histamine / Q000032:analysis; D006633:Histamine Antagonists; D006640:Histidine Decarboxylase / Q000187:drug effects / Q000378:metabolism*; D007274:Injections, Intraperitoneal; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology*; D051379:Mice; D008815:Mice, Inbred Strains; D010880:Piperidines / Q000494:pharmacology*; D013997:Time Factors
D006633:Histamine Antagonists; D008761:Methylhistamines; D010880:Piperidines; C069357:alpha-methylhistamine; D006632:Histamine; D006640:Histidine Decarboxylase; C052075:thioperamide