Distribution and physiological effects of B‐type allatostatins (myoinhibitory peptides, MIPs) in the stomatogastric nervous system of the crab Cancer borealis

Abstract

The crustacean stomatogastric ganglion (STG) is modulated by a large number of amines and neuropeptides that are found in descending pathways from anterior ganglia or reach the STG via the hemolymph. Among these are the allatostatin (AST) – B types also known as myoinhibitory peptides (MIPs). We used mass spectrometry to determine the sequences of nine members of the AST-B family of peptides that were found in the stomatogastric nervous system of the crab, Cancer borealis. We raised an antibody against Cancer borealis Allatostatin-B1 (CbAST-B1) (VPNDWAHFRGSWa) and used it to map the distribution of CbAST-B1-like immunoreactivity (-LI) in the stomatogastric nervous system. CbAST-B1-LI was found in neurons and neuropil in the commissural ganglia (CoGs), in somata in the esophageal ganglion (OG), in fibers in the stomatogastric nerve (stn), and in neuropilar processes in the STG. CbAST-B1-LI was blocked by preincubation with 10-6 M CbAST-B1, and partially blocked by lower concentrations. Electrophysiological recordings of the effects of CbAST-B1, CbAST-B2, and CbAST-B3 on the pyloric rhythm of the STG showed that all three peptides inhibited the pyloric rhythm in a state-dependent manner. Specifically, all three peptides at 10-8 M significantly decreased the frequency of the pyloric rhythm when the initial frequency of the pyloric rhythm was below 0.6 Hz. These data suggest important neuromodulatory roles for the CbAST-B family in the stomatogastric nervous system.

Inter-animal variability in the effects of C-type allatostatin on the cardiac neuromuscular system in the lobster Homarus americanus

“…The modulatory effects of C-AST in the lobster cardiac system clearly differ in detail from these effects, as they involve changes in the cycle frequency and duration of action potential bursts in pattern-generating neurons of the lobster CG, but not changes at the muscle or neuromuscular junction. Inhibitory effects of all three AST types (A-, B-and C-types) have been documented in the pyloric pattern generator of the stomatogastric system, but details of the mechanisms used to cause the observed decreases in cycle frequency have not yet been examined Dircksen et al, 1999;Fu et al, 2007;Ma et al, 2009;Szabo et al, 2011). Additionally, inhibitory effects of A-type allatostatins have been recorded in the crab CG (Cruz-Bermudez and Marder, 2007).…”

Functional consequences of neuropeptide and small-molecule co-transmission

“…5c). The GPRs are multi-transmitter sensory neurons containing ACh, 5-HT and AST 38,41,143,145,146 (FIG. 6Ab).…”

Mass spectrometric analysis of spatio-temporal dynamics of crustacean neuropeptides

“…Immunohistochemical (IHC) staining has long been a powerful tool for visualizing the distribution of neuropeptides in situ [42–46]. This antibody-based technique provides detailed spatial information of peptides with sub-cellular resolution when utilizing microscopy.…”