Intracellular recording and staining of tectal cells of the frog

839 FIBER CONNECTIONS OF THE CARP TORUS LONGITUDINAIJS..HIRONOBU ITO, HIDEO MASAI and REIJI KISHIDA*. Dept. Anat., Osaka Univ. Med. Sch., Nakanoshima 4-3, Kita-ku, Osaka 530, and Dept. Anat., Sch. Med., Yokok~ma City Univ., Urafuneeho 2-33, Minami-ku, Yokohama 232. The fiber connections of the carp torus longitudhnalis w e r e studied by means of degeneration, r e t r o g r a d e HRP, and electron microscopic methods. Efferent projections w e r e only seen in the m o s t superficial l a y e r of the optic teetum (stratum fibrosum marghmle). Afferent pathways to the torus longitudinalis were found to originate mainly in the valvula cerebelli. Degenerating fibers c o u r s e in the tractus me,~encephalocerebe[laris p o s t e r i o r within the valvula, and join *he tractu~3 m e s e n c e p h a l o c e r e b e l l a r i s a n t e r i o r in the tegmentum. The fibers which ascend in the t r a c t gradually ~lvade the optic rectum through which they a r e distributed to the torus longitudinally. The remaining fibers pass through the p o s t e r i o r c o m m i s s u r e and t e r m i n a t e in the torus longitudinalis a~ the r o s t r a l end of ~he tract. Synaptic patterns of the degenerating t e r m i n a l w e r e quite s i m i l a r to those of the m o s s y fiber termLlal in the cerebellum (I'['O, J . Morph., i35: 153, 1971). Degenerating t e r m i n a l s were also seen in the t~rus longimdinalis when lesions were made in other places (ITO and KISHIDA, J . Comp. Neur.~ 181: 465, 1978). The p o s s i bility of projections from those areas was discussed in ligh~ of the results of the r e t r o grade HRP method. I N T B A C E L L U L A R RECORP'-NG A N D STAINING O F T E C T A L C E L L ~ O F T H E F R O G . NOBUYOSHI MATSUMO'O and TOSHIHIRO B A N D O * . Dept. Biophysical Engineering, Fac. Engineering Scir;noe, Osaka Univ. Toyonaka, Osaka 560. Intracellular recording (Matsumoto et a l . , Proc. Japan Acad. 54 B, 386, 1978) and staining techniques w e r e applfed to the neurons o1: the frog optic tectum. Frogs w e r e anesthetized with ether and immobilized wi~h d-tubocurarine. Electrical stimulation was given at three points, one at the i p s i l a t e r a l optic ~ract and the ~ther two at the cont r i l a t e r a l optic nerve. T h i r t y - t h r e e cells o f 12 frogs were sampled, and t~ o r e s p o n s e ~:ypes were found. One was composed ol an EPSP followed by an IPSP (type I). The other was composed of two successive EPSPs followed by an IPSP (type II). Three cells w e r e classified as type H. Tectal delays of t h e i r initial EPSPs were 0.9, 1.0, and 1. l m s . These EPSP~ w e r e concluded to be produced monosynaptically through axons of retinal ganglion cells. Tectal delays of type I EPSPs ranged from 2 . 1 - 3 . 0 m s (2.5+0.25ms, ,1--30). These EPSPs w e r e presumed to be disynaptically produced, Conduction velocite~es of fibers had two peaks at 4 - 5 m / s and 6 - 8 m / s . The r mjor~ty of cells w e r e located at the depth of 300-450um. Intracellular staining with Procion Yellow revealed that type I responses w e r e : e c o r d ed from pyramidal or pear-shaped nem'ons in layer 6 and multipolar cells in l a y e r 8 and 7.