DISTRIBUTION AND EFFECTS OF TACHYKININ-LIKE PEPTIDES IN THE STOMATOGASTRIC NERVOUS-SYSTEM OF THE CRAB, CANCER-BOREALIS

The rhythmically active pyloric and gastric mill motor patterns in the stomatogastric ganglion of the crab, Cancer borealis, are influenced by modulatory projection neurons whose somata are located primarily in the other ganglia of the stomatogastric nervous system. One of these projection neurons exhibits substance P-like immunolabeling, However, bath application of substance P does not influence these motor pattern s. To determine whether a different peptide is responsible for the sub stance P-like immunolabeling, we studied the presence and physiologica l effects of the locustatachykinins and the leucokinins, two families of tachykinin-like peptides originally identified in insect nervous sy stems. Locustatachykinin-like immunolabeling has the same distribution in the stomatogastric nervous system as substance P-like immunolabeli ng and colocalizes with it in the majority of immunopositive structure s. Preincubation of locustatachykinin antibody with substance P, and p reincubation of substance P antibody with locustatachykinin, blocks su bsequent immunolabeling in the stomatogastric nervous system. In contr ast, we found no leucokinin-like immunolabeling in this system. Bath a pplication to the stomatogastric ganglion of individual locustatachyki nins or leucokinins excited the pyloric rhythm in a state-dependent ma nner. Each peptide family had distinct effects on the pyloric rhythm. Thus, both of these tachykinin-like peptide families are likely relate d to native neuropeptides that influence the pyloric rhythm. Furthermo re, a member of the locustatachykinin family is likely to be the sourc e of the previously identified substance P-like immunoreactivity in th e stomatogastric nervous system. (C) 1995 Wiley-Liss, Inc.