ラット外側視床下部の脳内自己刺激行動に対するThyrotropin-Releasing Hormoneの抑制効果

SUPPRESSIVE EFFECTS OF THYROTROPIN RELEASING HORMONE ON THE LATERAL HYPOTHALAMUS SELF-STIMULATION BEHAVIOR OF RATS

I．はじめに

　近年，種々の視床下部ホルモン分泌と脳内活性アミンとの関係が注目され興味ある知見が得られつつある。

　最近，Keller^5）は生化学的に，Constantinidisら^1）は螢光組織化学的に，Thyrotropin-Releasing Hormone（TRH）が祝床下部を含む脳内のnoradrenaline （NA）の代謝回転を促進させることを報告している。これらの実験事実は視床下部内のNA系終末部からのNAの放出がTRHによって促進されている可能性を強く示唆しており，彼等はTRHが脳内のNA系を賦活する効果を有しているのではないかと考えている。

Effects of TRH tartrate on the lateral hypo-thalamus self-stimulation (SS) behavior of rats werestudied in order to examine the influence of TRHtartrate on the function of noradrenergic system inmedial forebrain bundle.

5mg/kg of TRH tartrate tended to suppress theSS behavior. 10 mg/kg of TRH tartrate, transiently,suppressed the SS behavior for the first 30 minutesafter the injection of TRH tartrate. Especially,marked suppression of the SS behavior was observedimmediately after the injection of 20mg/kg ofTRH tartrate, and it tended to be restored after 60minutes. These effects of TRH tartrate (10mg/kgand 20mg/kg) significantly differed from those ofsaline control.

Suppression of the SS behavior by TRH tartrate(20mg/kg) was more markedly observed in thecase of low frequency SS rates with lower currentstimulus than in that of high frequency SS rateswith higher current.

Suppressive effect of TRH tartrate (20mg/kg) onSS behavior was antagonized by 0.5mg/kg ofmethamphetamine,

20mg/kg of TRH tartrate tended to suppress theSS behavior more strongly after the pretreatmentwith a-methyl-p-tyrosine (400 mg/kg).

These data obtained from the present experimentsuggest that TRH tartrate itself may suppress SSbehavior by its antagonistic action on the nor-adrenergic system in medial forebrain bundle of rats.