Morphological Studies On The Cells Of Nucleus Rotundus Projecting To Ectostriatum In The Chick

The birds visual system was mainly divided into two parallel processing pathways ofvisual information: the tectofugal pathway and the thalamofugal pathway. For poultry, thetectofugal pathway is more important than the thalamofugal pathway. The nucleusrotundus (Rt) lied the ventrolateral of thalami, was the largest nerve nucleus in thalami,was round or oval, surrounded by a fibrous capsule, and was the relay nucleus passed thevisual impulses from the optic tectum to the ectostriatum (Ect). In the tectofugal pathway,the nucleus rotundus is an important nucleus in the pathway, plays a major role in visualrecognition of color, brightness, graphics and so on. It is the important relay station of thevisual transmission. The ectostriatum is one of the two visual center in the endbrain, as atermination nucleus of the tectofugal pathway, The Ect received the fiber from the nucleusrotundus, nucleus under circle, nucleus triangularis, nucleus dorsolateralis thalami,hyperstriatum ventral and the main nucleus of feel, may be involved stimulus recognitionand visual cognition of the birds. To investigate the structural feature of the aviantectofugal pathway further. This study labeled cell somata morphology, size and fibrousconnection in Rt that projected to Ect by DiI (1,1′-dioctadecyl-3,3,3′3′-tetramethylindocarbo-cyanine perchlorate). Twenty one day-old chicks were deeplyanesthetized and perfused. In reference to the chicken brain map,10of them, the brain wastransversally cut through the region of Ect. Small crystals (2-3) of DiI were implanted inthe Ect under a dissection microscope in dark. The other10chickens fixed at the chickenbrain stereotactic instrument.10of them injected slowly small DiI solution into Ect by amicroinjector. Then the brains were immersed into tightlight-resistant containers in dark at37°C for about9weeks. Then the brain was cut by vibrating microtome and observedunder a fluorescence microscope. The result showed, after DiI implanted or injected intoEct, observed the overall structure of Rt and morphology of cells. Labeled Rt cells showedtriangular, pyriform, spindle, ovum and polygonal soma. Two different types of neurons,“typeⅠ c ells” and “type Ⅱ cells” were identified. The area of type Ⅰcells was578.38±285.97μm2and the dendritic field was366.01±174.73μm. The area of type Ⅱcells was625.37±265.87μm2and the dendritic field was322.91±173.09μm. The dendritesof the cells gave off several secondary dendrites, presented dichotomous. Based on the amount of the secondary dendrites, these cells were further divided into simple andcomplex cells, respectively. The statistical result showed, that most of the Rt cells weresmall cells, the middling cells have a limited number and the large cells have a smallnumber. Most of the dendritic field were narrow dendritic field, the middling dendriticfield have limited number and the wide dendritic field have small number.