2 research outputs found
Coordination of distinct but interacting rhythmic motor programs by a modulatory projection neuron using different co-transmitters in different ganglia
While many neurons are known to contain multiple neurotransmitters, the specific roles played by each co-transmitter within a neuron are often poorly understood. Here, we investigated the roles of the co-transmitters of the pyloric suppressor (PS) neurons, which are located in the stomatogastric nervous system (STNS) of the lobster Homarus americanus. The PS neurons are known to contain histamine; using RT-PCR, we identified a second co-transmitter as the FMRFamide-like peptide crustacean myosuppressin (Crust-MS). The modulatory effects of Crust-MS application on the gastric mill and pyloric patterns, generated in the stomatogastric ganglion (STG), closely resembled those recorded following extracellular PS neuron stimulation. To determine whether histamine plays a role in mediating the effects of the PS neurons in the STG, we bath-applied histamine receptor antagonists to the ganglion. In the presence of the antagonists, the histamine response was blocked, but Crust-MS application and PS stimulation continued to modulate the gastric and pyloric patterns, suggesting that PS effects in the STG are mediated largely by Crust-MS. PS neuron stimulation also excited the oesophageal rhythm, produced in the commissural ganglia (CoGs) of the STNS. Application of histamine, but not Crust-MS, to the CoGs mimicked this effect. Histamine receptor antagonists blocked the ability of both histamine and PS stimulation to excite the oesophageal rhythm, providing strong evidence that the PS neurons use histamine in the CoGs to exert their effects. Overall, our data suggest that the PS neurons differentially utilize their co-transmitters in spatially distinct locations to coordinate the activity of three independent networks. © 2013. Published by The Company of Biologists Ltd
Identification of SYWKQCAFNAVSCFamide: a broadly conserved crustacean C-type allatostatin-like peptide with both neuromodulatory and cardioactive properties
The allatostatins comprise three structurally distinct peptide families
that regulate juvenile hormone production by the insect corpora allata. A-type
family members contain the C-terminal motif –YXFGLamide and
have been found in species from numerous arthropod taxa. Members of the B-type
family exhibit a –WX6Wamide C-terminus and, like the
A-type peptides, appear to be broadly conserved within the Arthropoda. By
contrast, members of the C-type family, typified by the unblocked C-terminus
–PISCF, a pyroglutamine blocked N-terminus, and a disulfide bridge
between two internal Cys residues, have only been found in holometabolous
insects, i.e. lepidopterans and dipterans. Here, using transcriptomics, we
have identified SYWKQCAFNAVSCFamide (disulfide bridging predicted between the
two Cys residues), a known honeybee and water flea C-type-like peptide, from
the American lobster Homarus americanus (infraorder Astacidea). Using
matrix assisted laser desorption/ionization Fourier transform mass
spectrometry (MALDI-FTMS), a mass corresponding to that of SYWKQCAFNAVSCFamide
was detected in the H. americanus brain, supporting the existence of
this peptide and its theorized structure. Furthermore, SYWKQCAFNAVSCFamide was
detected by MALDI-FTMS in neural tissues from five additional astacideans as
well as 19 members of four other decapod infraorders (i.e. Achelata, Anomura,
Brachyura and Thalassinidea), suggesting that it is a broadly conserved
decapod peptide. In H. americanus, SYWKQCAFNAVSCFamide is capable of
modulating the output of both the pyloric circuit of the stomatogastric
nervous system and the heart. This is the first demonstration of bioactivity
for this peptide in any species