Substance P causes direct depolarisation of neurones of guinea pig interpeduncular nucleus in vitro

Abstract

SEVERAL lines of evidence suggest that the undecapeptide, substance P, is involved in synaptic transmission in various areas of the central nervous system¹. The development of a specific radioimmunoassay and new immunohistochemical techniques has allowed the identification of several specific but putative pathways involving substance P in the brain^2,3. In particular, the cell bodies in the medial habenula and probable nerve terminals in the interpeduncular nucleus contain high concentration of substanceP³. In addition, lesioning of the habenula causes a drastic decrease in the substance P concentration in the interpeduncular nucleus⁴. These findings imply that substance P may act as a transmitter in the habenulo-interpeduncular system. Therefore, in the present study, the effect of substance P has been examined in vitro on the interpeduncular neurones in an isolated guinea pig brain stem preparation. Substance P depolarised the membrane of the interpeduncular neurones. This finding supports the possible transmitter role of substance P in the central nervous system.