The effect of high pressure on the kinetics of monoamine transmitters in the rat brain.

The effects of 71 ATA pressure on the turnover of serotonin (5-HT), noradrenaline (NA), and dopamine (DA) were studied. High pressure increased the concentration of the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) by 40%. A concomitant increase in 5-HT synthesis (measured by the accumulation of 5-hydroxytryptophan after inhibition of the decarboxylase) of 25% was found. The changes in NA and DA metabolites and synthesis were smaller and not statistically significant. The increase in 5-HT synthesis was not a result of changes in the neuronal uptake of transmitter. The observed change might be the result of a compensatory increase in the activity of the serotoninergic neurons at high pressure. Among the three monoamine transmitter systems, that mediated by 5-HT may be most important in the pathogenesis of the high pressure neurologic syndrome.