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Hyperbaric He but not N2 augments Ca2+-dependent dopamine release from rat striatum
1Department of Pharmacology and Toxicology, University of Western Ontario, London, Canada.
Undersea Biomedical Research
|July 1, 1989
Summary
High pressure helium (He) significantly increases dopamine release in rat brain striatal slices, but only through a calcium-dependent pathway. Nitrogen (N2) at high pressures does not affect dopamine release.
Area of Science:
- Neuroscience
- Physiology
- Biochemistry
Background:
- Dopamine (DA) is a key neurotransmitter involved in motor control, reward, and other brain functions.
- High pressure environments, such as those experienced by divers, can affect neurological function.
- Understanding the effects of pressure on neurotransmitter release is crucial for explaining high pressure neurological syndrome.
Purpose of the Study:
- To investigate the effects of hydrostatic pressure from helium (He) and nitrogen (N2) on endogenous dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) release in rat brain striatal slices.
- To determine if pressure-induced changes in DA release are dependent on extracellular calcium.
- To explore the relevance of these findings to high pressure neurological syndrome and anesthetic reversal.
Main Methods:
- Endogenous dopamine and DOPAC levels were measured using high-performance liquid chromatography with electrochemical detection.
- Rat brain striatal slices were continuously superfused under various pressures of He and N2.
- Potassium chloride (K+) was used to evoke DA release.
- Experiments were conducted in both normal and calcium-free media.
- DA reuptake and metabolism were blocked using cocaine and pargyline.
Main Results:
- Helium (He) at 24 and 100 atmospheres absolute (ATA) significantly increased K+-evoked DA release (P < 0.01 and P < 0.05, respectively).
- He at 48 ATA did not significantly affect DA release.
- The pressure effect on DA release was primarily dependent on extracellular calcium.
- Nitrogen (N2) did not significantly alter DA release at any tested pressure (12-100 ATA).
- Blocking DA reuptake and metabolism showed a trend towards increased DA release under He pressure, but did not reach statistical significance.
Conclusions:
- Hydrostatic pressure exerted by helium augments calcium-dependent dopamine release in rat brain striatal slices.
- Nitrogen does not exhibit the same effect as helium under hydrostatic pressure.
- These findings contribute to understanding the mechanisms underlying high pressure neurological syndrome and potential pressure reversal by anesthetics.