In vivo release of neuronal histamine in the hypothalamus of rats measured by microdialysis.
Using an in vivo intracerebral microdialysis method coupled with an HPLC-fluorometric method, we investigated the extracellular level of endogenous histamine in the anterior hypothalamic area of urethane-anaesthetized rats. The basal rate of release of endogenous histamine in the anterior hypothalamic area measured by this method was 0.09 +/- 0.01 pmol/20 min. When the anterior hypothalamic area was depolarized by infusion of 100 mM K+ through the dialysis membrane or electrical stimulation at 200 mu A was applied through an electrode implanted into the ipsilateral tuberomammillary nucleus, histamine release increased to 175% and 188%, respectively, of the basal level. These increases were completely suppressed by removal of extracellular Ca2+. The basal release of histamine was also suppressed after infusion of 10(-6) M tetrodotoxin or i.p. administration of 100 mg/kg of alpha-fluoromethylhistidine. On the other hand, 3-fold increase in the basal release was observed after i.p. administration of 5 mg/kg thioperamide. These results clearly indicate that both the basal and evoked release of histamine measured by our method are of neuronal origin.
Mochizuki
T
T
Department of Pharmacology II, Osaka University Faculty of Medicine, Nakanoshima, Japan.
Yamatodani
A
A
Okakura
K
K
Takemura
M
M
Inagaki
N
N
Wada
H
H
D000818:Animals; D007025:Anterior Hypothalamic Nucleus / Q000378:metabolism*; D002118:Calcium / Q000502:physiology; D002851:Chromatography, High Pressure Liquid; D003956:Dialysis / Q000379:methods; D006636:Histamine Release / Q000502:physiology*; D006640:Histidine Decarboxylase / Q000037:antagonists & inhibitors; D008297:Male; D008762:Methylhistidines / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013779:Tetrodotoxin / Q000494:pharmacology
D008762:Methylhistidines; D010880:Piperidines; D013779:Tetrodotoxin; C028309:alpha-fluoromethylhistidine; D006640:Histidine Decarboxylase; C052075:thioperamide; D002118:Calcium