ABSTRACT
HRP solution (33%) was injected into the left superior colliculus of 21 adult albino rats. 1-2 days after injection, the animal was sacrificed. Brains were frozen sectioned and processed according to. DAB- or TMB-method. The labeled neurones were examined in the right superior colliculus and other areas of the brain. The resu ts are as follows:1. No matter where the HRP was injected (either in the rostral or caudal part of the superior colliculus or thepart between them) HRP labeled neurones were always observed on the opposite superior colliculus if the injection sites reached layers deeper than the stratum oPticum. The locations of the labeled neurones corresponded roughly to the sites of HRP injections. However, no HRP labeled neurones were observed when the core of HRP deposites was restricted to layers superficial to the stratum griseum intermediale.2. Of all labeled neurones, 53.6% were located in the stratum griseum intermediale, 16.5% in the stratum opticum. The rest were in deeper layers. In no case were HRP labeled neurones observed in the stratum zonale or stratum griseum superficiale.3. Labeled neurones could be classified morphologically into vertical fusiform, horizontal fusiform and multipolar neurones.4. In addition to the visual cortex, labeled neurones were also found in the inferior colliculi, paralemniscal nuclei, dorsal nuclei of the lateral lemniscus, substantia nigrae and lateral tegmental nuclei bilaterally. Labeled neurones were also found in the ipsilateral ventral nucleus of the lateral geniculate body, contralatera pretectal area and reticular formation.
ABSTRACT
In order to investigate the distribution and other features of callosal neurons inthe visual areas,12 adult albino rats were used in a series of experiments,in whichHRP(30～50%,DAB brown reaction)was injected into one hemisphere and theretrograde labelled cells were observed in the other hemisphere.1.Hardly any labelled neuron was found in contralateral visual cortices whenthe injections were made at sites within 3.6 mm from the midline of the brain.However,when the injections were made at sites 4～6 mm from the midline,manylabelled neurons could be observed.2.Generally,most labelled cells aggregated near the border between area 17 and18a.In area 18a numerous cells were labelled,which distributed in the form ofincontinuous patches.In the proper of area 17,however,less labelled cells werefound.3.A gross topographical correlation was observed between locations of injectionand labelling on the two hemispheres.4.The labelled cells were found in all cortical layers except layer Ⅰ.In area 17they were mainly in layers Ⅳ and Ⅴ,while in area 18 a they were found mainly inlayers Ⅲ,Ⅳ and Ⅴ.5.Some callosal neurons were lightly labelled.For these cells,only the outlinesof the cell body could be seen even under dark-field microscope.The diameters ofthese cells were about 8～10?m.A few cells were as large as 16?m in diameter.Other labelled neurons could be seen with both dark-field and bright-field illumina-tions.They were identified as pyramidal,multipolar bipolar and granular cells accordingto the shape of the cell bodies and the pattern of dendrites.The majority of labelledcells were pyramidal cells,with a long apical dendrite to the pia surface,10～20?min diameter.Other ceils were 10～20?m for multipolar cells,and less than 10?m forgranular cells.Comparisons were made between the above results and the physiological studies.