Morphological Observation On The Contralateral Projection Of The Tectofugal Pathway In Chick Brain

The shape, size and fiber connection of thalamus nucleus rotundus, optic tectum SGC, and SP/IPS in the contralateral projection within chick optical tectofugal pathway were studied using the carbocyanine dye DiI (1,1’–dioctadecyl -3,3,3’3’–tetramethylindocarbo -cyanine perchlorate ) and WGA-HRP tracing techniques to explore the he nerve regulation mechanism in affect of light on chick production performance. observed the shape and connections of the, the layer neural cells and nerve fibers and statistics the size of them. Thirty chickes of 1 day-old were perfused after deep anesthesia. The brains were transectioned from the nucleus Rotundus referenced the chick brain stereotaxic atlas. Two-three grains of DiI were implanted onto the nucleus rotundus under a dissecting microscope. After a incubation of 9 weeks at 37℃in a dark environment, the brains were removed and sliced into sections on the vibration microtome. The sections were observed under the fluorescence microscope in dark environment. In addition, 0.025μl 3% WGA-HRP solution was injected into the nucleus rotundus of sixty chicks of 16 day-old after anaesthetizing through the micro syringe according to the stereotaxic atlas of the chick brain. After a survival time of 30hs, they were perfused and made into the continuous frozen sections. The HRP labeled nerve cell were visualized using TMB method. The nerve cells and fibers in the sections were observed under an optical microscope. The results showed that after implanting DiI into the nucleus rotundus, the labled nerve cells in contralateral optic tectum were observed besides the ipsilateral side. They were mainly seen in the layer I, layer H and SGC. Most of their dendrites end in layer F. After a injecting of WGA-HRP into nucleus rotundus, the labeling were obviously seen in the dorsalateral of contralateral nucleus rotundus, being mainly nerve fibers and having fewer cell bodies. In the same coronal plane, if WGA-HRP is injected into the center of the nRt, and diffused to the entire nRt from center to the edge, the labeled nerve cells and fibers concentrated mostly in the dorsal of the concentrated Rt, occupied approximately 1/3 of its area. If the injection center near the inside or inside dorsal of the nRt, the nerve cells and fibers concentrated mostly in the medial dorsal of the contralateral Rt, they are in a mirror symmetry relations with the inject region, occupied approximately 1/4-1/2 of its area. If the injection center is in the ventral of the nRt, the nerve cells and fibers mosty concentrated on the inside of the center of the contralateral nRt, occupied approximately 1/4-1/2. In different coronal planes of a contralateral nRt, the concentrated locations of nerve cells and fibers are different. The number of labeled nerve cells in the contralateral optic tectum layer SGC is more. The labeled nerve fibers could be seen in the dorsal supraoptic decussation, and they arranged into fascicular. Connected the ipsi- and contralateral nucleus of the tectofugal pathway. There is no other access like this be observed. It suggested that both sides of nucleus rotundus projected to each other. The projection between the contralateral SGC and nRt is monodirectional and from the contralateral SGC to the inject side nRt. The projection between the contralateral SP/IPS and nRt is also monodirectional and from inject side nRt to the contralateral SP/IPS. There is no access like the dorsal supraoptic decussation, and it can be observed that all the contralateral projections must get through the dorsal supraoptic decussation. The projection could make the specific units combined and managed the messages came from binoculus, being helpful for the cerebrum to gain more exact and overall messages.