China Rana (rana Chensinensis) Tadpole Embryo Development Of Gaba In The Distribution Of The Cells

Theγ-aminobutyric acid(GABA) is a major inhibitory neurotransmitter in the central nervous system(CNS) of vertebrates.The distribution of neural GABA in mammals and fish has been well established,but the distribution information in amphibians is limited and there are still some questions in phylogenesis of GABAergic systerm in anuran amphibians due to little information.In this study,Rana chensinensis adult and larva were used as experimental animals,investigated the distribution and variation of GABAergic cells in the brain of R.chensinensis during postembryonic development by histology and immunohistochemistry.The main results and conclusions as follows:1.The morphological characteristics in brain of R.chensinensis tadpoles during postembryonic development were:(1) the cerebral hemisphere perfected gradually,at the same time, the cavity of lateral ventrical enlarged and extended to caudal part,until stage 39 reached the adult level.(2) At stage 32,the optic lobe ventriculus appeared in midbrain,cells and fibers of optic lobe began to layered distribution around the potic lobe ventriculus.(3) The cerebellum enlarged and upheaved constantly,it was a long strip structure similar to adult at stage 35.At stage 46 the cerebellar valvula appered in midventricle.These changes in brain of tadpoles were closely related to terrestrial environment adaption,body balance maintenance,muscle tone temperance,action coordination and space positioning when the metamorphosis completed.2.GABAergic cells were widely distributed in telencephalon,diencephalon,midbrain,and myelencephalon of adult R.chensinensis.The existence of GABAergic cells in cerebral cortex, preoptic area,tegmentum,optic chiasma and torus semicircularis demonstrated that GABAergic cells were involved in control of olfaction,audition,vision and vocalization.3.In R.chensinensis tadpoles during early postembryonic development(at stage 28-32), GABAergic cells were detected in olfactory bulb,it was suggested that GABA was atrophic factor during the development of olfactory bulb.GABAergic cells in telencephalon of tadpoles were detected in pallium,spetum,amygdale,striatum and nucleus accumbens.The quantity of GABAergic cells in primordial hippocampus,spetum and amygdale increased significantly when the metamorphosis completed,GABAergic cells in these structures were involed in olfactory integration, visceral activities,endocrine and motion regulation.It was supposed that the increased number of GABAergic cells were closely related to the changes of motion mode and feeding hatit of froglet.4.In R.chensinensis tadpoles,GABAergic cells in diencephalon were detected in preoptic area and suprachiasmatic nucleus,and the quantity of GABAergic cells in these two nucleuses increased significantly when the metamorphosis completed.It was suggested that R.chensinensis in terrestrial environments was more sensitive to the temperature change and light stimulation.In R. chensinensis tadpoles at stage 28-35,GABAergic cells were detected in ventral bypothalamic nucleus,it was suggested that GABA might mediate hypothalamic control over the neuroendocrine system in early postembryonic development.5.In R.chensinensis tadpoles,sparse GABAergic cells were detected in torus semicircularis of midbrain.The quantity of GABAergic cells in torus semicircularis increased significantly when the metamorphosis completed which could be induced by more sensitive to sound signals in terrestrial environments.6.In R.chensinensis tadpoles,GABAergic cells were detected in solitary tract nucleus of myelencephalon,it was indicated that GABAergic cells were involved in the regulation of respiratory movement and gastroenteric activity.In summary,as an important neurotransmitter in the central nervous system of amphibians,it was supposed that the significant changes of GABA in metamorphosis due to the great changes of nervous systerm in metamorphosis in order to adapt to the new environment.