Plasma Neurotransmitters Throughout an Oral Glucose Tolerance Test in Non-Depressed Essential Hypertension Patients

The oral glucose tolerance test (OGTT) with plasma neurotransmitter assays and blood pressure measurements were performed on 68 hypertensive (A and B) and 68 paired normal controls (group C). Those patients who failed to show significant or persistent blood pressure reductions throughout OGTT constitute group A (37 subjects); and those who did show significant and persistent reductions constitute group B (31 subjects). The purpose of this study was to assess if there were any significant differences between those patients whose blood pressure levels normalized throughout OGTT and those who didn't and, further, compare them to their controls. In group A, noradrenaline (NA) was high at the 0' (fasting) period, increasing further at 60' and 90'; however, circulating serotonin (p5HT) did not vary throughout OGTT. Group B, although showing high NA at 0', did not show rises afterwards; whereas, significant and sustained p5HT rises registered throughout postprandial periods. In group C, both p5HT and plasma NA showed significant and sustained increases. Therefore, the NA/p5HT ratio is higher in A, than in B and C. Group A patients were awake and alert throughout. Group B patients were mostly drowsy and many slept light and intermittently. Group C subjects slept throughout, dreaming and showing rapid eye movements. Our findings suggest that the hypertensive syndrome is most severe in those patients who do not show a rise in postprandial circulating serotonin (parasympathetic activity), group A, than those who do exhibit such a rise, group B.