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Synchronized clusters of action potentials can increase or decrease the excitability of the axons of magnocellular
1Department of Anatomy, University of Cambridge, Cambridge, UK. red1000@cus.cam.ac.uk
Journal of Neuroendocrinology
|August 6, 2000
Summary
Stimulating supraoptic nucleus (SON) cells in rats revealed that brief subthreshold stimuli increase excitability, while longer suprathreshold trains paradoxically decrease it, impacting hormone secretion.
Area of Science:
- Neuroscience
- Cellular Physiology
Background:
- The supraoptic nucleus (SON) plays a crucial role in regulating hormone secretion.
- Understanding the excitability of SON neurons is vital for comprehending physiological processes.
Purpose of the Study:
- To investigate the effects of different stimulus trains on the excitability of SON cell axons and terminals in vivo.
- To determine how these excitability changes influence neuronal firing and hormone release.
Main Methods:
- Extracellular recordings were performed on SON cells in anesthetized male rats.
- Antidromic activation was achieved using stimulating electrodes placed at mid-axon and axon terminals.
- Trains of subthreshold and suprathreshold stimuli were applied to assess changes in activation thresholds.
Main Results:
- Short trains of subthreshold stimuli decreased activation thresholds, indicating increased excitability.
- Longer trains of suprathreshold stimuli paradoxically increased activation thresholds, showing decreased excitability.
- Both increased and decreased excitability were observed at axons and terminals of oxytocin and vasopressin cells.
Conclusions:
- Stimulation patterns significantly alter SON neuron excitability in vivo.
- These dynamic changes in excitability likely influence action potential propagation and hormone secretion under physiological conditions.