Abstract: AIM: To observe and compare the anatomic distribution of tyrosine hydroxylase(TH)-positive neurons in the pons of alligator sinesis/Chinese alligator, domestic chickens and rats for collecting the comparative anatomy data for investigation of the biological evolution and population protection of Chinese alligator.METHODS: Totally, Chinese alligators (n=6), domestic chicken (n=15) and Sprague-Dawley (SD) rats (n=15) of either sex were included and cross-grouped into three groups with 2 alligators, 5 chicken and 5 rats for each. Animals in the three groups were simultaneously sacrificed by electric shock. The expressions of TH in pons were detected by immuno-histochemical assay and HemaGSM 2000P analysis.RESULTS: Conglomerated or diffused distribution of the TH positive neurons were commonly seen in pons in alligator sinesis, domestic chicken and rats. The TH positive cells presented with diverse cellular morphology by shapes of oval, roundness, spindle or polygon, whereas the cell number in different morphology varied a lot in pons among the three animals(P<0.01). The TH reactive neurons were primarily middle-sized or small-sized in the pons in the three kinds of animals, and large-sized cells were in relatively low number. Nevertheless, significantly increased reactive neurons to TH was seen in corresponding segments of the pons from chickens and rat as compared with alligator sinesis (P<0.01), and the gray value was also reduced evidently (P<0.01). In addition, the TH positive neurons in the pons of rats were increased greatly, but decreased significantly in gray value, when compared with the chicken's(P<0.01).CONCLUSION: The TH positive neurons were increased in turn in the pons of the Chinese alligators, domestic chickens and rats, the average gray value for the cells were decreased ordinally, and the number for diverse cellular morphology were not proportional. These findings suggest that TH distribution differences may be associated with different species of function area carries out its related nervous systems function in the pons.

Key words: Alligator sinensis, Chicken, Rat, Pons, Tyrosine hydroxylase