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Choline acts as agonist and blocker for Aplysia cholinergic synapses
Journal of Neurophysiology
|January 1, 1984
Summary
Choline acts as a partial agonist in Aplysia neurons, affecting synaptic responses even without apparent conductance changes. This unexpected action influences synaptic transmission by altering current components and their voltage dependence.
Area of Science:
- Neuroscience
- Neurophysiology
- Marine Biology
Background:
- Neurons in Aplysia buccal ganglia are known to respond to choline.
- Choline is sometimes used as a sodium substitute in physiological experiments.
Purpose of the Study:
- To investigate the specific actions of choline on identified neurons in Aplysia.
- To characterize the effects of choline on synaptic currents and their components.
Main Methods:
- Iontophoretic application of choline and acetylcholine (ACh) to voltage-clamped neurons.
- Analysis of postsynaptic currents (PSCs) and their reversal potentials.
- Bath application of choline to assess effects on synaptic depression and duration.
Main Results:
- Choline produced curare-blockable currents similar to ACh, with 10-100% of ACh response amplitude.
- Bath choline depressed IPSC amplitude and prolonged IPSC decay, suggesting partial agonist activity.
- Choline selectively activated the late outward current component in diphasic PSPs, while blocking it.
Conclusions:
- Choline exhibits partial agonist activity in Aplysia neurons, influencing synaptic transmission.
- Choline's effects extend beyond simple conductance changes, altering synaptic depression and duration.
- The voltage-dependent properties of synaptic current components contribute to functional outcomes.