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Hypothalamic GABA suppresses sympathetic outflow to the cardiovascular system
J H Wible1, F C Luft, J A DiMicco
1Department of Medicine, Indiana University School of Medicine, Indianapolis 46223.
The American Journal of Physiology
|April 11, 1988
Summary
Altering gamma-aminobutyric acid (GABA) in the rat posterior hypothalamus impacts cardiovascular function. Suppressing GABAergic inhibition increases sympathetic activity, while enhancing it decreases it in conscious rats.
Area of Science:
- Neuroscience
- Cardiovascular Physiology
Background:
- The posterior hypothalamus plays a role in regulating cardiovascular function.
- GABAergic signaling is a key inhibitory neurotransmitter system in the brain.
Purpose of the Study:
- To investigate the cardiovascular effects of modulating GABAergic tone in the rat posterior hypothalamus.
- To determine the role of GABA in controlling sympathetic nerve activity originating from this brain region.
Main Methods:
- Rats were surgically prepared with cannulas in the posterior hypothalamus and catheters for physiological monitoring.
- Microinjections of GABA antagonists (bicuculline, picrotoxin) and agonist (muscimol) were administered.
- Cardiovascular parameters (heart rate, blood pressure) and sympathetic nerve activity were recorded in conscious and anesthetized rats.
Main Results:
- GABA antagonists increased heart rate, blood pressure, and sympathetic nerve activity in conscious rats.
- GABA agonist decreased these parameters in conscious rats.
- GABA agonist had no effect in anesthetized rats, indicating a tonic inhibitory influence in conscious states.
Conclusions:
- The posterior hypothalamus harbors a sympathoexcitatory system modulated by GABAergic tone.
- GABAergic inhibition tonically suppresses this system in conscious rats, an effect masked by anesthesia.