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Intracellular Recording, Sensory Field Mapping, and Culturing Identified Neurons in the Leech, Hirudo medicinalis
Published on: November 4, 2013
Dopamine activates the motor pattern for crawling in the medicinal leech
1Graduate Program in Neuroscience, and Department of Entomology, University of Minnesota, Saint Paul, Minnesota 55108, USA.
Summary
Dopamine (DA) activates fictive crawling in medicinal leeches, demonstrating its sufficiency in initiating motor programs. This research reveals that the core crawling control, or unit burst generator, resides within each segmental ganglion.
Area of Science:
- Neuroscience
- Animal Behavior
- Motor Control
Background:
- Locomotion in segmented animals relies on coupled "unit burst generators."
- The biological basis of these generators is understood in few systems.
- Dopamine (DA) is a known modulator of motor activity.
Purpose of the Study:
- To determine if dopamine (DA) is sufficient to activate fictive crawling in the medicinal leech.
- To investigate if the unit burst generator for crawling exists within a single segmental ganglion.
Main Methods:
- Isolated nerve cords and single segmental ganglia of medicinal leeches were used.
- Dopamine (DA) was applied to induce and record neuronal activity.
- Fictive crawling was analyzed by observing motoneuron bursting patterns and phase relationships.
- Quantitative analysis compared DA-induced crawling with electrically evoked and spontaneous crawling.
Main Results:
- Dopamine (DA) induced slow, antiphasic bursting in motoneurons (DE-3, VE-4, CV) with a 15s period, consistent with crawling.
- In single ganglia, inhibitory motoneurons (DI-1, VI-2) fired out of phase with DE-3, confirming the crawl unit burst generator.
- DA-induced fictive crawling in isolated ganglia was robust, lasting 5-15 minutes and comparable to other crawling methods.
Conclusions:
- Dopamine (DA) is sufficient to activate the complete crawl motor program in medicinal leeches.
- The fundamental unit burst generator for crawling is located within each segmental ganglion.
- This finding localizes the neural kernel for locomotion to the smallest division of the central nervous system.
