脳内自己刺激（側座核）とmicroinjection （中脳腹側被蓋野）—procaineおよびapomorphineの場合

EFFECTS OF PROCAINE AND APOMORPHINE INJECTED INTO THE VENTRAL TEGMENTAL AREA ON SELF-STIMULATION OF THE NUCLEUS ACCUMBENS

I．はじめに

　Nucleus accurnbens （NAS）は，mesolimbic dopaminesystem （A₁₀）の起始部位であるventral tegmental area（VTA）からその神経投射を受けると同時に錐体外路系と大脳辺縁系との間に，入出力の神経回路網を形成している^2,10,12）。先に著者ら^15）は，GABA拮抗物質（picro—toxin）をVTAにmicroinjectionし，NASの脳内自己刺激（intracranial self-stimulation：ICSS）にそれが促進的な影響を与えることを報告し，GABAergic intera—ctionもまたNASのICSSに関与する可能性を指摘した。今回は，これらの一連の実験として，procaineとapomorphineをVTAにmicroinjectionして，VTA自身の機能変化が，NASのICSSにいかなる作用をおよぼすかを検討した。

In the present study, microinjection of procaine and apomorphine were made into the ventral tegmental area (VTA) during self-stimulation of the nucleus accumbens (NAS). By blocking the VTA input to NAS with procaine, it should be possible to influence self-stimulation of the NAS. In addition, since it has been suggested that dendrites of VTA dopaminergic neurons contain dopamine "autoreceptors", the effect of micro-injections of apomorphine, a dopamine agonist, into the VTA on self-stimulation of the nucleus accumbens was also investigated. Result obtained were as follow:

The injection of procaine to VTA reduced self-stimulation of the ipsilateral NAS and the admin-istration of apomorphine to the VTA significantly attenuated self-stimulation of the ipsilateral NAS completely suppressing it for 3-4 min. Self-stimu-lation of NAS has been suggested to activate fiber projection of mesolimbic dopaminergic neurons (A₁₀) from VTA.