Study On The Cytoarchitecture Of Tectal SGC And Distribution Of Some Neuropeptides Within The OT-Rt Pathway In Chick

Cytoarchitecture and development of stratum griseum central (SGC), morphological feature of the SGC cells which project to Rt, were studied by DiI retrogradely labeling, Nissl staining and Golgi-Cox staining. By Nissl staining, the average width of dorsal, ventral and the lateral regions were 154.50±23.66μm, 3.02±24.17μm, and 18.29±33.85μm (n=298), it indicated that the width of dorsal region in SGC was thinner than those of the ventral and the lateral regions. The soma of the cells appeared triangular, polygonal, oval or spindle. Some of triangular soma and the spindle one gave out 2～3 primary dendrites and had bigger dendrites field. Some polygonal soma and triangular ones sent more dendrites and had smaller dendrites field. According to the somatic area, these cells can be divided into large cells (S＞100μm~2), medium cells (S50～100μm~2) and small cells (S＜50μm~2). About 90% of the SGC cells were large and medium ones. Observation on the development of the SGC showed that the average width in E11, E14, E17 and E20 were 122.73±24.80gm, 141.17±37.65μm, 163.31±25.73μm,and 167.43±31.18μm (n=20). It indicated that the rapid period of development occurred in E11～E17, the slow period of development was in E17～E20. Considered the width of SGC of three-day-old chick, it can be deduced that in 1～3 days after hatching, another development summit occurred. Using immunohistochemistry method, the GABA, GnRH, VIP andβ-END-like immunoreaction positive neurons within the OT-Rt pathway were observed in the different photoperiod. The photoperiod was designed into four levels. They are 11L:13D, 13L:11D, 15L:9D, and 17L:7D. The GABA-like immunoreaction positive neurons could be seen in SGC, n.SP/IPS and n.Rt in 11h and 13h photoperiod. The positive neurons within SGC and n.Rt in13h photoperiod are more than those in the 11h photoperiod. The positive neurons within n.SP/IPS in 11h photoperiod are more than those in the 13h photoperiod. The GnRH-like immunoreaction positive neurons could be seen in SGC, n.SP/IPS and n.Rt in 11h and 13h photoperiod. There were more positive neurons in SGC and less in n.SP/IPS in the 13h photoperiod. VIP-like immunoreaction positive neurons could be seen in the OT-Rt pathway in 11h,13h and 15h photoperiod. Quantity of the posotive neurons in SGC and n.SP/IPS was most in 13h photoperiod, the neurons in n.Rt were most in 11h photoperiod.β-END-like immunoreaction positive neurons appeared in SGC, n.SP/IPS and n.Rt in 11h,13h and 17h photoperiod. The results indicated that GABA may be the important inhibitory neuropeptides, VIP, END also involved in the regulation of the GnRH. Optical information may control the chicken production performance by adjusting the distribution of GABA, VIP andβ-END neuropeptides within the OT-Rt pathway.