STUDIES ON THE STEREOTAXIC APPARATUS AND BRAIN ATLAS OF THE HOUSE MUSK SHREW

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The house musk shrew ( Suncus murinus ) has been domesticated by S.Oda and K.Kondo as new laboratory animal, and was named "suncus". It has been revealed that the suncus has various unique characteristics in the central nervous system and endocrinological control systems.The purposes of this project are to contrive a stereotaxic apparatus applicable to the suncus and to decide the stereotaxis coordinate of the suncus brain.Body size of the suncus is similar to those of young rats or mice, but stereotaxic apparatus for small rodents can not be used for suncus, because the suncus has very different anatomical features of head region from rodents:(1) tympanic bulla and external acustic meatus are not bony but membranous or, a part, cartilageous. (2)external acustic pore of the suncus shifts far ventrally. and axis between the pores of both side runs through larynx. Ear-bars contrived to be applicable to the suncus in this study are more thick and short than those used for rodents; apical diameter is 3mm. basal diameter is 5mm and length is 5mm, and resin pad of 10mm diameter is attached to basal part. These ear-bars can fix tightly head of the suncus, and do not put pressure upon larynx from lateral sides.Temporal plane of skull of the suncus is not round but straight on oral-aboral axis. When this temporal plane is kept horizontally by adjustment of teeth-bar, cerebral temporal surface is also kept horizontal. Under above mentioned condition, the vertical transverse profile through ear-bar 0 plane contains caudal end of the longitudinal cerebral fissure and caudal pole of the mamillary body. This plane is used as the transverse 0 plane of stereo- taxic coordinate in this study. Planes which are parallel to the temporal plane and run through ear-bars or teeth-bar can not be used for horizontal standard plane. because those are too ventrally shifted from the brain. Brain surface is used as horizontal 0 plane in this study.