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CHOLINE ESTERASE AND THE THEORY OF CHEMICAL MEDIATION OF NERVE IMPULSES.
1Carlsberg Laboratory, Copenhagen.
The Journal of General Physiology
|October 30, 2009
Summary
This study measured choline esterase activity in cat superior cervical ganglia, finding it crucial for rapid acetylcholine breakdown. Enzyme localization within ganglion cells is necessary for nerve impulse transmission.
Area of Science:
- Neuroscience
- Biochemistry
- Enzymology
Background:
- Acetylcholine is a key neurotransmitter in the autonomic nervous system.
- Choline esterase is the enzyme responsible for acetylcholine hydrolysis.
- Understanding enzyme kinetics is vital for neural function.
Purpose of the Study:
- To quantify the maximum choline esterase activity in the cat superior cervical ganglion.
- To determine the time course of acetylcholine destruction after nerve impulse.
- To investigate the role of enzyme localization in synaptic transmission.
Main Methods:
- Measurement of enzyme activity using acetyl choline chloride substrate.
- Determination of the dissociation constant for the enzyme-substrate reaction.
- Calculation of acetylcholine hydrolysis rates and refractory period implications.
Main Results:
- Maximum choline esterase activity was 0.10gamma acetyl choline chloride/sec/mg tissue at pH 7.4 and 38°C.
- The minimum time for acetylcholine destruction by one nerve impulse is 0.015sigma.
- The dissociation constant was 0.001, indicating a hydrolysis time of approximately 8 seconds at minimum rate.
Conclusions:
- Enzyme and substrate localization within the ganglion cell is essential.
- This localization ensures rapid acetylcholine enzymatic destruction within the refractory period.
- The findings support a model for efficient synaptic transmission in the superior cervical ganglion.
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