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Extrinsic modulation and motor pattern generation in a feeding network: a cellular study
1Sussex Centre for Neuroscience, University of Sussex, Falmer, Brighton, BN1 9QG, United Kingdom. V.Straub@sussex.ac.uk
Summary
The cerebral giant cells (CGCs) in snails modulate feeding circuits by releasing serotonin (5-HT). This study reveals how 5-HT alters neuron properties, controlling feeding motor patterns at a cellular level.
Area of Science:
- Neuroscience
- Cellular Biology
- Molluscan Physiology
Background:
- Gastropod mollusks utilize cerebral giant cells (CGCs) for extrinsic modulation of feeding central pattern generators (CPGs).
- Serotonin (5-HT) is a key neurotransmitter released by CGCs, influencing CPG activity.
Purpose of the Study:
- To investigate the cellular-level modulatory actions of CGCs and 5-HT on feeding CPG neurons.
- To elucidate the specific effects of serotonergic input on motoneuron properties within the feeding CPG.
Main Methods:
- Isolation of Lymnaea snail motoneurons (B4, B8, B4CL) from the nervous system.
- Pharmacological examination of isolated motoneurons in cell culture.
- Coculture of motoneurons with CGCs to compare 5-HT effects with direct CGC stimulation.
Main Results:
- 5-HT caused prolonged depolarization and firing in all three motoneuron types.
- Conditional bursting was observed in B4/B8 cells, with frequency modulated by CGC firing rate.
- 5-HT application increased postinhibitory rebound (PIR) in all motoneurons via a CsCl-sensitive current.
Conclusions:
- Serotonergic modulation by CGCs significantly impacts motoneuron membrane potential, bursting, and PIR.
- These cellular effects are crucial for motoneuron activation during feeding in Lymnaea.
- CGCs likely exert system-level gating and frequency control through these modulatory actions on feeding motoneurons.