脳内自己刺激とその随伴行動—第2報：Supracallosal bundle （SCB）とPrefrontal cortex （PFC）の場合

SELF-STIMULATION OF SUPRACALLOSAL BUNDLE (SCB) AND ITS ASSOCIATED BEHAVIOR COMPARING TO THOSE OF PREFRONTAL CORTEX (PFC).

I．はじめに

　ペダルを押すと自動的に定電流が脳報酬系に流れるように慢性電極を植えこむと，ラットはペダルを押し続ける。このような脳内自己刺激（intracranial self-stimu—lation：ICSS）について著者らは^4,12,13）これまで一連の実験を報告してきたが，今回はprefrontal cortex （PFC）の下に付立置するsupracallosal bundle （SCB）とPFCのICSS頻度を対比するとともに，その随伴行動も観察した。また，ICSSの実験が終つた後，同じラットを急牲実験にもちこみ，SCB-ICSS陽性電極を刺激して，iateral hypothalamus （LH）のspontaneous unit dis—charge （SUD）におよぼす影響を観察した。

　OldsとMilner^6）が発見したICSS法を使つて，脳の報酬系に関与する神経機構と，それに伴う行動を探ることは，精神病におけるanhedoniaと行動異常を研究する一つのけ方法であると考える。

The supracallosal bundle (SCB) and prefrontal cortex (PFC) recieve projection from medial forbrain bundle (MFB) of the lateral hypothalamus (LH) in relation to reward system. The major purpose of the present study was to compare the intracranial self-stimulation (ICSS) rate of both the SCB and PFC with special emphasis on its associated behavior.

The results obtained were as follows:

1) The self-stimulation was obtained with electrodes historogically varified as being in the SCB (16 of 23 electrodes positive for ICSS) and the medial PFC (3 of 16 electrodes positive for ICSS). Electrodes dorsal and far lateral to the SCB and PFC were mainly negative (see Fig.1).

2) Rats with SCB or PFC electrodes, chiefly showed a rearing associated with its ICSS. When stimulation electrodes were more posterior or lateral sites in the SCB and PFC, clonic move-ments of forelimb and head were occasionally observed (Fig.1).

3) For neurons in the LH, stimulation of the SCB via chronic electrodes positive for ICSS produced two characteristic types, i.e.postinhibitory rebound type (Fig.2 A) and driven inhibitory type (Fig. 2 B-1). It was suggested that fibers of MFB were activated by stimulating SCB-ICSS sites.