Microtubule-associated protein-2 and neurofilament immunoreactivity in neurons and small, intensely fluorescent cells of an amphibian cardiac ganglion.

The localization of two cytoskeletal proteins was analysed in the cell bodies and processes of ganglionic neurons and small, intensely fluorescent cells of the parasympathetic cardiac ganglion of Necturus maculosus (mudpuppy). Antibodies against microtubule-associated protein-2 and against the highly phosphorylated isoforms of high and middle molecular weight neurofilament subunits were used as somatodendritic and axonal markers, respectively. The ganglionic neurons, which usually have only one major process, and small, intensely fluorescent cells, which have several processes, showed distinctly different staining patterns with the two antibodies. In control and denervated ganglia, the ganglionic cell bodies and several hundred micrometers of the proximal processes were labeled with the antibody against microtubule-associated protein-2, whereas small, intensely fluorescent cells and processes showed a paucity of immunoreactivity. The neurofilament antibody labeled numerous axons in the ganglion but did not label the proximal part of the postganglionic process or small, intensely fluorescent cell processes. Denervation resulted in the presence of phosphorylated neurofilament subunit immunoreactivity in the soma and proximal process of the ganglionic neuron. These data suggest that (i) small, intensely fluorescent cells and ganglionic neurons in the mudpuppy cardiac ganglion contain distinctly different cytoskeletal proteins, (ii) the proximal part of postganglionic "axons" contains dendrite-like and not axon-like cytoskeletal proteins, and (iii) deafferentation promotes the localization of phosphorylated forms of neurofilament subunits in the soma and proximal process of parasympathetic ganglionic neurons.