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Multiple peptides converge to activate the same voltage-dependent current in a central pattern-generating circuit
1Volen Center and Biology Department, Brandeis University, Waltham, Massachusetts 02454, USA.
Summary
Six substances activate the same inward current in crab neurons, demonstrating convergence despite distinct receptors. Differential responses depend on receptor distribution, influencing network activity.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Marine Biology
Background:
- The stomatogastric ganglion in crustaceans like Cancer borealis is a model system for studying neural circuit function.
- Numerous neuropeptides and other substances modulate stomatogastric ganglion activity, influencing neuronal firing patterns.
- Proctolin, a neuropeptide, induces a specific inward current with outward rectification in these neurons.
Purpose of the Study:
- To investigate the ionic currents underlying the effects of proctolin and five other modulators on Cancer borealis stomatogastric ganglion neurons.
- To determine if these diverse modulators converge onto a common ionic current.
- To explore the role of receptor distribution in mediating differential neuronal responses.
Main Methods:
- Voltage clamp electrophysiology was employed on stomatogastric ganglion neurons, both in intact ganglia and dissociated cell cultures.
- Currents evoked by proctolin, C. borealis tachykinin-related peptide Ia (CabTRP Ia), crustacean cardioactive peptide, red pigment-concentrating hormone, TNRNFLRFamide, and pilocarpine were analyzed.
- Experiments included varying extracellular calcium concentrations and using a calmodulin inhibitor to probe current properties and signaling pathways.
Main Results:
- All six tested substances induced currents with similar voltage-dependent properties, characterized by outward rectification that linearized in low extracellular calcium.
- The lateral pyloric neuron responded to all six modulators, while the ventricular dilator neuron showed a more restricted response profile.
- Proctolin and CabTRP Ia responses occluded each other, and a calmodulin inhibitor affected responses to both, suggesting convergence onto a shared current.
Conclusions:
- All six modulatory substances converge on the same voltage-dependent inward current in stomatogastric ganglion neurons.
- Despite activating different receptors, the ultimate downstream effect is mediated by this common current.
- Differential network responses to these modulators are likely determined by the specific distribution of their respective receptors across different neurons.