ORGANIZATION OF THE STOMATOGASTRIC NEUROPIL OF THE CRAB, CANCER-BOREALIS, AS REVEALED BY MODULATOR IMMUNOCYTOCHEMISTRY

We used antibodies to a number of neuromodulatory substances, includin g serotonin, FLRF Amide, red pigment-concentrating hormone, substance P, proctolin and cholecystokinin, to investigate the distribution of m olecules similar to these substances in the stomatogastric ganglion of the crab, Cancer borealis. No immunoreactivity was seen in the region of the cell bodies that surrounds the neuropil and little was found i n the core of the neuropil (where the primary neurites of the intrinsi c neurons occupy most of the space). Instead, modulator immunolabel wa s densely packed in the more peripheral portion of the neuropil that s urrounded the core. Within this peripheral neuropil, profiles appeared quite uniformly distributed. Double-labeling showed that there were l imited differences in distribution between the labels examined in our study. The only immunolabeled structures that showed a distinct differ ential distribution within the stomatogastric neuropil were a populati on of greater than or equal to 10 mu m Varicosities that arose from a pair of input fibers that we termed the large varicosity fibers. These varicosities were immunolabelled by antisera for three different pept ides. Taken collectively, these data shows that there is a stereotyped distribution of modulator immunoreactivity within the crab stomatogas tric neuropil. However, this segregation is more rudimentary than that reported for the intrinsic stomatogastric neurons.