Two subpopulations of ganglion cells in hydra are distinguished by an immunogold-double-labeling technique

Abstract

In the primitive nervous system of Hydra sensory cells and ganglion cells are easily distinguished by their location and distribution, but distinguishing subpopulations within these two groups of neurons is difficult. Both sensory cells and ganglion cells in Hydra and other coelenterates can be immunocytochemically stained with antisera against the molluscan cardio-excitatory neuropeptide FMRFamide as well as other peptides with the general structure < Glu... Arg-X-NH2, where X is an aromatic amino acid. Arg-Phe-amide (RFamide)-like peptides have be e n localized in densecored vesicles of ganglion cells in the peduncle of Hydra. but to date there is no ultrastructural evidence to distinguish between subpopulations of ganglion cells. Therefore, we used an immunogold-double-labeling procedure for electron microscopy with antisera to FMRFamide and RGamide (Arg-Gly-amide) to determine if these two peptides characterized different types of ganglion cells in the peduncle and lower part of the hypostome. In addition, we tested for colocalization of RFamide- and Antho-RFamide-like material in the same neuronal dense-cored vesicles.