Morphological study of cultured cardiac ganglionic neurons from different postnatal stages of rats

This study sought to establish a culture model of cardiac ganglia (CG) neurons of the Sprague-Dawley (SD) rat which could by used to study the distinct characteristics of CG neurons. After culturing, the morphology and immunocytochemistry of CG neurons obtained on different days after birth were compared. Samples of CG neurons were taken from the posterior atrial wall of rats aged 7, 14, 21 and 40 postnatal days (designated as P7, P14, P21 and P40, respectively). During 3-6 days of culture, the morphological changes of the cultured neurons were monitored using a light microscope. Immunocytochemical staining of the neurofilaments (NF-L, -M and -H) was performed to identify the CG neurons and the changes in morphology. The differences in size of the CG soma of each culture were compared by morphometry. Frozen sections of CG neurons were used as the in vivo control of the above experiments. The results showed that the rate of growth in size of the CG soma was highest in the P7 group, and was slower after weaning (21 days after birth). Cultured neurons were categorized into unipolar-like (Type I), multipolar-like (Type II), and bipolar-like (Type III) based on their morphological characteristics. In NF immuocytochemical staining, there were strong responses to NF-H and NF-M in all cultures, but not to NF-L. More specifically, responses to NF-H were mainly observed in perikaryons and neurites, whereas the responses to NF-M were mainly in perikaryons. The present study has established a culture system for cardiac ganglia neurons of SD rats. Our results show that the intracardiac neurons were still developing in their somata and the processes and that various responses to different antibodies of NF for CG neurons occurred in different postnatal stages in rats.