lucifer-yellow and phenylalanyl-leucyl-arginyl-phenylalaninamide

Phylogenetic comparison can reveal general principles governing the organization and neuromodulation of neural networks. Suitable models for such an approach are the pyloric and gastric motor networks of the crustacean stomatogastric ganglion (STG). These networks, which have been well studied in several species, are extensively modulated by projection neurons originating in higher-order ganglia. Several of these have been identified in different decapod species, including the paired modulatory proctolin neuron (MPN) in the crab Cancer borealis [Nusbaum & Marder (1989) J. Neurosci., 9,1501-1599; Nusbaum & Marder (1989), J. Neurosci., 9, 1600-1607] and the apparently equivalent neuron pair, called GABA (gamma-aminobutyric acid) neurons 1 and 2 (GN1/2), in the lobster Homarus gammarus [Cournil et al. (1990) J. Neurocytol., 19, 478-493]. The morphologies of MPN and GN1/2 are similar, and both exhibit GABA-immunolabelling. However, unlike MPN, GN1/2 does not contain the peptide transmitter proctolin. Instead, GN1/2, but not MPN, is immunoreactive for the neuropeptides related to cholecystokinin (CCK) and FLRFamide. Nonetheless, GN1/2 excitation of the lobster pyloric rhythm is similar to the proctolin-mediated excitation of the crab pyloric rhythm by MPN. In contrast, GN1/2 and MPN both use GABA but produce opposite effects on the gastric mill rhythm. While MPN stimulation produces a GABA-mediated suppression of the gastric rhythm [Blitz & Nusbaum (1999) J. Neurosci., 19, 6774-6783], GN1/2 activates or enhances gastric rhythmicity. These results highlight the care needed when generalizing neuronal organization and function across related species. Here we show that the 'same' neuron in different species does not contain the same neurotransmitter complement, nor does it exert all of the same effects on its postsynaptic targets. Conversely, a different transmitter phenotype is not necessarily associated with a qualitative change in the way that a modulatory neuron influences target network activity.

Topics: Animals; Brachyura; Cholecystokinin; Electrophysiology; Fluorescent Dyes; gamma-Aminobutyric Acid; Isoquinolines; Nephropidae; Nervous System; Neural Pathways; Neurons; Neuropeptides; Oligopeptides; Periodicity; Phylogeny; Species Specificity; Stomach

To compare the stomatogastric nervous system of the crayfish Cherax destructor with those of other decapod species, the distribution of FLRF (Phe-Leu-Arg-Phe) amide-, proctolin- and crustacean cardioactive peptide (CCAP)-like immunoreactivities was studied in the stomatogastric nervous system and in neurosecretory structures by using wholemount immunocytochemical techniques and confocal microscopy. In addition, the number of cells in the stomatogastric ganglion (19-24) and axon profiles in the stomatogastric nerve (157-165) were counted. FLRFamide-like immunoreactivity was present within numerous cell bodies and neuropil of the commissural ganglia, in the neuropil of the stomatogastric ganglion, and in one cell body of the esophageal ganglion. FLRFamide-like immunoreactivity was also found in two cell bodies at the junction of the stomatogastric nerve with the superior esophageal nerve and in two cell bodies in the inferior ventricular nerve. Proctolin-like immunoreactivity was present in numerous cell bodies and neuropil of the paired commissural ganglia and in the neuropil of the stomatogastric ganglion. CCAP-like immunoreactivity was found in the neuropil and in one to four cell bodies in the commissural ganglia. Both proctolin- and CCAP-immunoreactive varicosities occurred on the surface of the circumesophageal connectives and on the postesophageal commissure, indicating a neurohemal source within the stomatogastric nervous system, which was verified by electron microscopy. The pericardial organs showed FLRFamide-, proctolin-, and CCAP-like immunoreactivity. This staining pattern suggests that FLRFamide-like and proctolin-like peptides are used as neurohormones and as neuromodulators in the stomatogastric nervous system of the crayfish C. destructor, whereas CCAP-like peptides may only affect the stomatogastric ganglion as a neurohormone.

Topics: Animals; Astacoidea; Axons; Biotin; Brain Chemistry; Calcitonin; Female; Fluorescent Dyes; Ganglia, Invertebrate; Immunohistochemistry; Isoquinolines; Male; Microscopy, Electron; Neurons; Neuropeptides; Oligopeptides; Peptide Fragments