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Resistive loading reduces ventilatory response to strychnine in anesthetized rabbits
S Delpierre1, E Balzamo, Y Jammes
1Laboratoire de Physiologie Respiratoire, Faculté de Médecine Timone, Marseille, France.
Neuroscience Letters
|December 5, 1998
Summary
Glycine weakly inhibits breathing during inspiratory resistive loading (IRL). Blocking glycine receptors with strychnine increased ventilation in resting rabbits but not during IRL, suggesting IRL reduces glycine's effect on the respiratory network.
Area of Science:
- Neuroscience
- Respiratory Physiology
Background:
- Inspiratory resistance causes hypoventilation despite increased diaphragmatic activity.
- GABA and opioid neurotransmitters partially explain inadequate respiratory drive during inspiratory loading.
Purpose of the Study:
- To investigate the role of glycine, an inhibitory neurotransmitter, in respiratory control during inspiratory resistive loading (IRL).
- To evaluate the effects of the glycine antagonist strychnine on ventilation and diaphragmatic activity in rabbits under normal and loaded breathing conditions.
Main Methods:
- Anesthetized rabbits were studied under two conditions: normal breathing and breathing through an inspiratory resistive load (IRL).
- The glycine antagonist strychnine was administered to assess its effects on minute ventilation and integrated diaphragmatic discharge (Edi).
Main Results:
- Strychnine increased minute ventilation and diaphragmatic activity in control (unloaded) rabbits.
- During IRL, strychnine did not significantly alter minute ventilation and produced a smaller increase in diaphragmatic activity compared to controls.
- Strychnine induced a tonic diaphragmatic discharge in both groups.
Conclusions:
- Glycine exerts a weak inhibitory influence on inspiration during inspiratory resistive loading.
- The efficacy and/or release of glycine in the central nervous system appear reduced during IRL.
- These findings suggest that glycine's role in modulating respiratory drive is diminished under conditions of inspiratory resistance.