Development of renovascular hypertension after central serotonin depletion

5-HT in systemic hypertension: foe, friend or fantasy?

Since its discovery by Erspamer in the 1930s and identification by Page in the 1950s, 5-HT (5-hydroxytryptamine; serotonin) has been an elusive candidate as a substance that plays a role in the disease of high blood pressure, also known as hypertension. In both animal and human hypertension, arterial contraction to 5-HT is profoundly enhanced. Additionally, 5-HT is a vascular smooth muscle cell mitogen. Because both increased arterial contractility and smooth muscle growth contribute to the disease of hypertension, it is logical to believe that 5-HT is a potential cause of disease, and thus a foe. However, decades of research have produced conflicting results as to the potential role of 5-HT in hypertension. This review will discuss historical findings which both support and refute the involvement of 5-HT in hypertension, and pose some new questions that may reveal novel ways for 5-HT to modify vascular control of blood pressure.

Effect of EXP 3174 on blood pressure of normoreninemic renal hypertensive rats

This study examined the effect on mean blood pressure of a new orally active nonpeptide angiotensin II (Ang II) receptor antagonist, EXP 3174, in doses that completely block exogenous Ang II action. Anesthetized and conscious two-kidney, two clip chronic renovascular hypertensive rats and sham-operated animals were used. In anesthetized hypertensive rats, intracerebroventricular administration of the inhibitor had no effect on blood pressure, whereas blood pressure was normalized by intravenous injection of the antagonist (163 +/- 12 to 110 +/- 9 mm Hg, P < .05). In sham anesthetized rats, intravenous injection of EXP 3174 also lowered blood pressure (112 +/- 6 to 96 +/- 6mm Hg, P < .05). In conscious rats, intravenous EXP 3174 induced a fall in pressure that was larger in hypertensive (156 +/- 9 to 132 +/- 5 mm Hg, P < .05) than in sham (104 +/- 3 to 94 +/- 4 mm Hg, P < .05) rats. Plasma renin activity was very high in anesthetized animals (hypertensive versus sham, 87.8 +/- 8.3 versus 95.7 +/- 10.2 ng Ang I/mL per hour); differences were not significant either between anesthetized hypertensive and sham or in conscious animals (hypertensive versus sham, 9.42 +/- 1.58 versus 6.74 +/- 2.32 ng Ang I/mL per hour). Angiotensinogen concentration was higher in cerebrospinal fluid in anesthetized hypertensive rats (36.4 +/- 3.0 versus 26.0 +/- 2.4 ng Ang I/mL, P < .05) and in the artery wall of hypertensive conscious rats (103.1 +/- 10.3 versus 75.2 +/- 7.8 ng Ang I/g, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood pressure regulation in Alzheimer's disease

Brain neurons which regulate blood pressure (BP), including the C-1 tonic vasomotor neurons, degenerate in Alzheimer's disease (AD). This study determines whether BP is decreased in AD. We reviewed records of three autopsy proven AD patients. Medical causes for decreased BP were investigated. Yearly averages for systolic (SBP), diastolic (DBP), mean arterial (AP) blood pressure and pulse pressure (PP) were calculated. BP in the year of diagnosis was compared to the sum of all BP in subsequent years. In addition, each yearly measurement through the course of AD was compared to its counterpart in the year of diagnosis. Three BP measurements were significantly decreased by from 6.9% to 15.9% in all patients when BP in the year of diagnosis was compared to the sum of each pressure in subsequent years. Sustained BP declines started in the third to fourth year after diagnosis of AD and continued for up to 9 years. The PP was decreased by 19.9% in one patient. There was a strong correlation between the number of C-1 neurons in these cases and their AP and SBP in the years after diagnosis. Hypothalamic phenylethanolamine N-methyltransferase activity was decreased by 63% in AD compared to control cases. Neurofibrillary tangles were found in the paraventricular nucleus of the hypothalamus in an AD case. We postulate that BP is altered in AD as neurons which regulate it degenerate.