In mammals, several groups of cardiac ganglia (CG) are sparsely distributed in the posterior wall of the atrium and the interatrial septum. The CG from early postnatal rats were cultured for optimum observation of cellular morphology and direct access to neurons for immunohistochemical analysis. During the two weeks observation period, CG neurons were immunocytochemically stained with neuron-specific enolase (NSE) or calcitonin gene-related peptide (CGRP). Results showed that one day after cultivation cells migrated out from the cultured cells mass. After 4 days of culture, isolated or aggregated neurons dispersed on the flattened fibroblasts layer. Most neurons are multipolar and contain an eccentric oval nucleus. Two neuron types were observed, type I neurons, characterized by a few, short cytoplasmic processes, were numerous; type II neurons, characterized by many long branching processes with beaded enlargements, were isolated and few in number. Some cultured neurons showed NSE immunoreactivity (IR), in which, both type I neurons and type II neurons expressed strong NSE-IR in soma and processes. Alternately, CGRP-IR was found in the perikarya of type I neurons only. This study showed that the tissue culture system could identify two types of growing CG neurons which may indicate that CG neurons do not play the same physiological role, and need more investigation. Further study is required to identify the relationship between the two types of neurons.
Cardiac ganglia, Tissue culture, NSE, CGRP
