In vivo rate of serotonin synthesis in brain and spinal cord of young, spontaneously hypertensive rats.

The accumulation of 5-hydroxytryptophan (5-HTP) following decarboxylase inhibition was measured in hypothalamus (HYP), pons-medulla (PM) and spinal cord (SC) of 4- and 8-week-old spontaneously hypertensive (SH) and normotensive (WKY) rats. Using this method, a significant increase in the in vivo activity of tryptophan hydroxylase was observed in the PM and SC of 4-week-old, but not 8-week-old SH rats. These findings show a transient elevation in rate of 5-HT synthesis prior to the onset of hypertension, which does not appear to continue during the maintenance phase.