Abstract
We investigated the fine structure of Phe-Met-Arg-Phe(FMRF)amide-containing peptidergic neurons in the stomatogastric nervous system of the American cockroach by immunoelectron microscopy. Immunoreactive cell bodies were located in both the ingluvial and proventricular ganglia. Besides those ganglionic cells, several extraganglionic cell bodies within the esophageal and ingluvial nerves also contained this peptide. Immunopositive nerve fibers bearing bead-like swellings or varicosities, ran mainly along the circular muscle cells in the foregut, but no specialized neuromuscular junctions were found. The fibers contained large core vesicles (100 and 180 nm in diameter) which were thought to package this peptide, as well as small clear vesicles. These results suggest that the peptidergic neurons might have plural types of neurotransmitters, and innervate the musculature in a non-synaptic manner.
