Abstract: Nissl staining and immunohistochemical staining method were used to morphologically characterize the cerebellum of the new-hatching Yangtze alligator Alligator sinensis， and the distribution of 5-HT and DA in the cerebellum of the new-hatching Yangtze alligator was investigated for the first time. The results showed that there was a ventriculus cerebelli in the cerebellum of the new-hatching Yangtze alligator and the surface of the cerebellar cortex was not very smooth but with irregular folds. Two cerebellar nuclei termed as the nucleus cerebelli lateralis and the nucleus cerebelli medialis were found in the medulla of cerebellum. The results also showed the cerebellar cortex could be divided into four layers which included external granular layer (EGL), molecular layer (ML), Purkinje cell layer (PCL) and granular layer (GL). Purkinje cell layer could be characterized specially by multilayer. In the transverse sections, the 5-hydroxytryptamine-immunoreactive (5-HT-IR) and dopamine-immunoreactive (DA-IR) cells were detected in the EGL; the 5-HT-IR and DA-IR Purkinje cells were also found; there were 5-HT-IR fibers in the ML and GL, the DA-IR fibers could also be found in the ML and GL; a lot of 5-HT-IR and DA-IR fibers were detected in the medulla; the cell bodies of cerebellar nucleus were also detected 5-HT-IR; the substance of CSF was found DA-IR. In the sagittal sections, there were 5-HT-IR cells and DA-IR fibers in the EGL; there were also 5-HT-IR and DA-IR fibers in the ML and GL; the ependymal cells were not detected 5-HT-IR and DA-IR; the cells of the choroid plexus (CP) were found lightly 5-HT-IR and strongly DA-IR. The abundance of 5-HT and DA in cerebellum suggested that these highly conserved neurotransmitters would play important roles in motor control.

Key words: 5-hydroxytryptamine, dopamine, new-hatching Alligator sinensis, cerebellum, immunohistochemistry