Different Types Of Hypertension Research Articles

Hemodynamic and neurohumoral profile in patients with different types of hypertension in pregnancy

Hypertension in pregnancy is a frequent disorder that includes a spectrum of conditions. We aimed at comparatively evaluating the hemodynamic, echocardiographic and biohumoral profile of a sample of pregnant Caucasian women with different form of pregnancy-related hypertension. We enrolled 39 non-hypertensive pregnant women (NP), 26 with Chronic HBP in pregnancy (CH), 24 with gestational hypertension (G-PIH), and 33 with pre-eclampsia. We recorded and compared blood pressure (BP), echocardiographic parameters, resting plasma renin activity (PRA) and plasma aldosterone (PA), Plasma levels of atrial (ANP) and brain natriuretic peptide (BNP). PE patients had a significantly higher BP than either G-PIH or NP patients. PE patients had also significantly lower cardiac output than NP, G-PIH and CH. In comparison to NP patients, the total peripheral vascular resistance was 61% higher in PE women and 38% higher in CH patients. All echographic parameters were significantly more altered in PE patients when compared with NP, in respect to any other form of hypertension. Either ANP (+35%) and BNP (+40%) were significantly higher in PE patients than in controls. The PRA was reduced in PE and CH patients when compared either with NP (-38 and -35%, respectively) or G-PIH (-47 and -43%, respectively). On the basis of our data, we can conclude that PE is the gestation associated hypertension with the largest anatomical, functional and biohumoral involvement, and so it has to be involved in a more intensive monitoring and evaluation.

Hypertensive Disorders in Normal/Over-weight and Obese Type 2 Diabetic Pregnant Women

Hypertension is one of the major complications of pregnancy. Its impact in type 2 diabetic pregnant women could be understimated because it is generally evaluated by retrospective studies and as one of the outcome measures. Our aims were: 1) to evaluate the prevalence of hypertensive disease between type 2 diabetic and normal pregnancies; 2) to relate hypertensive disease to body weight in type 2 diabetic pregnancies; 3) to assess the impact of different types of hypertension on pregnancy outcome in type 2 diabetic women. Seventy-six type 2 diabetic (23 normal-weight, 26 overweight and 27 obese) and sixty normal (43, 15 and 2 respectively; x (2) 0.0001) pregnancies, matched for age and smoking habit. Hypertension was defined as >/=140/90 mmHg and classified in chronic, gestational and pre-eclampsia. Student's t-test, chi (2), simple, and/or multiple and logistic regression analysis were used when appropriate. Odds ratio was calculated for hypertension. p significant <0.05. The overall prevalence of hypertension was 40.8% (18.4% chronic, 17.1% gestational and 5.3% pre-eclampsia) in type 2 diabetic pregnancies and 10% (8.3% gestational and 1.7% pre-eclampsia) in normal pregnancies (p<0.0001), with an odds ratio of 6.2. All the types of hypertension, significantly chronic, contributed to the higher prevalence. Only in diabetic pregnancies, hypertension was associated with a higher pregestational BMI; whenever BMI increased, chronic and gestational hypertension increased by contrast of pre-eclampsia (chi (2), 0.02). Hypertensive disorders did not affect maternal-fetal outcome. The prevalence of hypertension was 40.8% in type 2 diabetic pregnant women whilst it was 10.0% in non diabetic controls. All hypertensive disorders, significantly chronic, were more frequent. Increasing BMI was a crucial factor for chronic and gestational but not for pre-eclampsia. Hypertensive diseases did not seem to affect pregnancy outcome.

The combination of atenolol and amlodipine is better than their monotherapy for preventing end‐organ damage in different types of hypertension in rats

Combinations therapy is often used in hypertensive patients whether combination therapy is necessary for preventing end-organ damage is not known. The objective of this study was to determine in four different hypertensive animal models the necessity of adding the calcium channel blocker amlodipine to therapy with the ß-blocker atenolol to modulate end-organ damage. Spontaneously hypertensive rats, DOCA-salt hypertensive rats, two-kidney, one-clip renovascular hypertensive rats and Lyon genetically hypertensive rats were used to study this objective. These animal models have different sensitivities to atenolol and amlodipine. The dosages of therapy employed were 10 mg/kg atenolol alone, 1 mg/kg amlodipine, 10 mg atenolol + 1 mg/kg amlodipine and 5 mg/kg atenolol+0.5 mg/kg amlodipine. BP was continuously recorded in all animals. After determination of baroreflex sensitivity, rats were sacrificed for end-organ damage evaluation. The combination of amlodipine and atenolol had a synergistic inhibitory effect on blood pressure and blood pressure variability, and end-organ damage as compared with monotherapy with atenolol or amlodipine in all animal models. Baroreflex sensitivity also improved with the combination therapy more than with monotherapy. In conclusion, atenolol and amlodipine combination exerts a superior effect on blood pressure, blood pressure variability, baroreflex sensitivity and end-organ damage. The superior effect of the combination was observed in all four models of hypertension.

Placental morphometrical and histopathology changes in the different clinical presentations of Hypertensive Syndromes in Pregnancy

Even though there are clinical studies emphasizing the diagnosis and the perinatal intercurrent diseases of the Hypertensive Syndromes in Pregnancy, few of these studies establish the clinical forms of the specific hypertensive syndromes with the associated morphological placental alterations. The lack of studies on placental morphology and the etiopathogenesis of the different clinical standards for HSP, together with the need to objectively characterize these morphological placental lesions justify this study. A retrospective study was carried out with 91 placentas examined throughout the period from 2000 to 2003. All placentas from patients presenting HSP in this period were included in the study. These were classified according to features well established by the literature such as laboratory and clinical criteria into: gestational hypertension (GH), chronic hypertension (CH), pre-eclampsia (PE) and pre-eclampsia superimposed on chronic hypertension (PSCH). The number of knots presented a positive correlation with the length of time and severity of the hypertension during gestation (Spearman correlation: 0.253; P = 0.0158). The fibrin deposit was greater in all HSP groups but the pattern of distribution changes in the most severe cases from perivillous to intravillous as in the PSCH group (P = 0.002). There was no statistically significant difference in the area of the stem vessel walls among the groups. The cases with PE and CH presented a larger number of terminal villi vessels (P < 0.001). This report suggests, that although they could be different types of hypertension or an evaluation of the same disease, the final pathway that leads to microscopic lesions in the placenta is the same, with only different intensity due to the severity of the disease.

Comparison of lipid profiles in normal and hypertensive pregnant women

Comparison of lipid profiles in normal and hypertensive pregnant women

Does Endothelial Nitric Oxide Synthase Gene Variation Play a Role in the Occurrence of Hypertension in Pregnancy?

Objective: Nitric oxide is suggested to play a role in the development of preeclampsia. Methods: We studied 61 patients with gestational hypertension (GH), 77 with GH and significant proteinuria (urine protein excretion ≥ 300 mg/24 h), 82 with essential hypertension (EH) and 188 normotensive women with at least one normal pregnancy. Main Outcome Measure(s): A polymorphism within the constitutive endothelial nitric oxide synthase (ecNOS) gene in various types of hypertension in pregnancy was explored. Results: Allelic and genotypic frequencies did not differ between controls and case groups. A significant difference was observed between the frequency of the rare allele in GH patients and that in EH group (χ2: 4.47, P < .04). This difference approximated the significance when GH subjects with or without proteinuria were grouped (χ2 square: 3.33; P = .068). Cigarette smoking or gravidity did not interact with the ecNOS polymorphism in identifying different types of hypertension in this setting. Conclusion: Our findings argue against an association between ecNOS polymorphism and preeclampsia and support the hypothesis for a different pathogenesis of GH in respect to EH.

PRORENIN CONCENTRATION IN THE HYPERTENSIVE DISORDERS IN PREGNANCY

Objective: To evaluate the plasma prorenin levels during the three trimesters of normal pregnancy, their prognostic value, and their correlation with hypertensive disorders of pregnancy.Design: A prospective study in which plasma prorenin and renin levels were measured in 55 healthy pregnant women and 66 who developed gestational hypertension or preeclampsia. The patients were classified as mild preeclampsia (mild PE), severe preeclampsia (severe PE), chronic hypertension and superimposed preeclampsia upon chronic hypertension (superimposed PE).Method: Venous blood samples were collected in the first, second and third trimesters and during delivery or cesarean. Plasma renin concentration (PRC) was measured by radioinmmunoassay before and after incubation with trypsin solution. The difference gave plasma prorenin concentration (PProRC).Results: PRC and PProRC were significantly higher in pregnant women compared with healthy non-pregnant. PRC was significantly increased in the first trimester in the chronic hypertension group and a lower value was found in the first trimester in the superimposed PE compared with those in healthy pregnant women. No differences in other groups were found. PProRC showed a significant lower value in the first and third trimesters in the severe PE group. In the superimposed PE a low value of PProRC similar to those of non-pregnant women was found.Conclusions: The results show that the different types of hypertension in pregnancy have different profiles of PProRC and PRC in relation to development of preeclampsia. The absence of increase of PProRC in the first trimester of superimposed PE may have a prognostic value.

Lipid peroxide and vitamin E patterns in pregnant women with different types of hypertension in pregnancy

OBJECTIVES: We sought to evaluate the circulating levels of lipid peroxides and vitamin E and the placental levels of lipid peroxides in pregnant women with different types of hypertension. STUDY DESIGN: Lipid peroxides were measured in serum and placental tissue by the thiobarbituric acid method and high-pressure liquid chromatography, and vitamin E was measured by high-pressure liquid chromatography. The patients studied were 36 healthy pregnant women and 92 women with hypertension classified as having mild gestational hypertension ( n = 28), severe gestational hypertension ( n = 10), preeclampsia ( n = 34), and chronic hypertension ( n = 20). RESULTS: Lipid peroxides in serum and placental tissue were significantly increased, and vitamin E levels in serum were significantly decreased in women with severe gestational hypertension and preeclampsia compared with controls. The groups of mild gestational hypertension or chronic hypertension had similar values of lipid peroxides or vitamin E as controls. CONCLUSIONS: Our results suggest that the category of gestational hypertension may be composed of at least two entities with different pathophysiology and support the concept of nonproteinuric preeclampsia. (Am J Obstet Gynecol 1998;178:1072-6.)

Nitric oxide in different types of hypertension during pregnancy.

1. Serum nitric oxide (NO) levels (determined by its products of oxidation) were assessed in non-pregnant women, normal pregnant women and patients suffering from mild pre-eclampsia (MPE), severe pre-eclampsia (SPE), chronic hypertension (CHT) and CHT with pre-eclampsia (CHT + PE). The levels of NO products were significantly reduced during pregnancy in MPE (P < 0.001), CHT + PE (P < 0.01) and SPE (P < 0.05). Significant reductions of NO products were also observed in puerperium (P < 0.001) in all groups except CHT + PE (P < 0.05). 2. In normal pregnancy, three events were related to NO levels: (1) negative correlations were found between the levels of nitrite (r = -0.73, P = 0.0003), nitrate (r = -0.53, P = 0.017) and the number of weeks of gestation; (2) in the caesarean section group, the levels of NO at puerperium were significantly lower (P < 0.05) than those during pregnancy; and (3) there was a significant reduction in NO levels in the pregnant women carrying male fetuses as compared with female fetuses (P < 0.05). 3. In SPE, the patients with a family history of hypertension had lower levels of NO compared with the patients without such a history (P < 0.05). 4. A negative correlation was observed between systolic blood pressure, diastolic blood pressure and NO levels in MPE (r = -0.62, P = 0.013 and r = -0.68, P = 0.0049 respectively) and SPE (r = -0.72, P = 0.004 and r = -0.53, P = 0.037 respectively). 5. In SPE, positive correlations were observed between platelet count and nitrite (r = 0.67, P = 0.006) and nitrate levels (r = 0.56, P = 0.028). 6. In MPE, patients with anti-hypertensive treatment showed significantly (P < 0.05) higher levels of NO compared with the non-treated patients. 7. NO may be important in the physiopathology of hypertension during pregnancy, although several factors may affect its levels.

Variation in lipid levels during pregnancy in women with different types of hypertension.

To evaluate the levels of serum lipids (cholesterol and triglycerides) in pregnant women with different types of hypertension, at the first, second and third trimesters of pregnancy. Cholesterol and triglyceride levels at the first, second and third trimesters of gestation were recorded for 115 women with hypertension during pregnancy, and 115 healthy pregnant women matched for age and body mass index. Cases were classified as having mild gestational hypertension (25), severe gestational hypertension (15), mild preeclampsia (20), severe preeclampsia (20), chronic hypertension (20), and superimposed preeclampsia (15). Cholesterol levels were not statistically different between cases and controls in any form of hypertension. At 20 and 34 weeks' gestation, triglyceride levels were significantly higher than controls in women with severe gestational hypertension, mild and severe preeclampsia, and superimposed preeclampsia, but not in mild gestational hypertension or chronic hypertension. The significant elevation in triglycerides was already present at 10 weeks in mild and severe preeclampsia. The data suggest that the alterations in lipid metabolism observed in preeclampsia are already present at the first trimester of pregnancy. Women with severe gestational hypertension presented a pattern of triglycerides similar to that of preeclamptic women, but mild gestational hypertension resembled chronic hypertension in this respect. This supports the concept that, although in many cases gestational hypertension represents latent essential hypertension, some of these women, probably the most severe cases, present with true pregnancy-induced hypertension, or nonproteinuric preeclampsia.

Genetic variation at the angiotensinogen locus in relation to high blood pressure and myocardial infarction

To study the association between polymorphisms of the angiotensinogen (AGT) gene and blood pressure in population-based samples, and to determine whether genetic variation at the AGT locus is involved in the susceptibility to myocardial infarction. The study population comprised 630 cases who survived a myocardial infarction, recruited from the World Health Organization Monitoring Cardiovascular Diseases registers in Belfast, Lille, Strasbourg and Toulouse, and 741 controls drawn from the corresponding populations. The AGT polymorphisms investigated were T174M and M235T. High blood pressure was defined as diastolic blood pressure > 100 mmHg or the use of antihypertensive medication, or both. In the controls the mean +/- SEM frequency of the M174 allele was 0.116 +/- 0.008, and that of the T235 allele was 0.401 +/- 0.013. In the whole population blood pressure levels and prevalence of high blood pressure did not vary according to T174M and M235T genotypes. However, obesity appeared as a crucial factor influencing the relationship between high blood pressure and T174M. In subjects with body mass index < 26 kg/m2 there was a 2.4-fold increase of the prevalence of high blood pressure in carriers of the M174 allele compared with in homozygotes for the T174 allele, whereas no association was detected in subjects with body mass index > 26 kg/m2. The association between high blood pressure and M235T was not significant in either group. The T174M and M235T genotype distributions did not differ between survivors of myocardial infarction and controls. These data suggest that the AGT gene could be involved in the predisposition to high blood pressure in non-overweight, but not in overweight men, possibly reflecting genetically different types of hypertension. No significant impact of the AGT locus in the risk of non-fatal myocardial infarction was detected.

Circulatory and Plasma Catecholamine Responses to Mental Stress in Young Subjects with two Different Types of Hypertension

To determine whether any differences exist between young male subjects with elevated diastolic and systolic blood pressure (BP) and those with only an elevated systolic BP, the responses of BP and plasma catecholamines to a mental arithmetic test were studied in 11 young men (mean age of nineteen years) with BP of ≥ 140/90 mm Hg at a routine health check-up (group I-hypertension [HT]), 26 age-matched men with only elevated systolic BP (≥ 140 mm Hg) (group II-HT), and 12 age-matched normotensive (NT) men (&lt; 140/90 mm Hg). During an arithmetic test, group I-HT showed a significantly higher increment of systolic BP (+14.5-18.0%) than group II-HT (+9.3-10.2%) and NT controls (+6.4-8.2%). However, no significant difference in BP response was seen between group II-HT and NT controls. Plasma norepinephrine in group I-HT showed a significant increase after the test, (171 ±23 → 202 ±27 pg/mL), whereas group II-HT and NT controls showed no change. No significant difference occurred in epinephrine response among the three groups. These results suggest that the young male subjects with screening BP above 140/90 mm Hg are hyperreactive to a mental stress as compared with subjects with only elevated systolic BP or NT controls.

Circulatory and Plasma Catecholamine Responses to Mental Stress in Young Subjects with two Different Types of Hypertension

To determine whether any differences exist between young male subjects with elevated diastolic and systolic blood pressure (BP) and those with only an elevated systolic BP, the responses of BP and plasma catecholamines to a mental arithmetic test were studied in 11 young men (mean age of nineteen years) with BP of > or = 140/90 mm Hg at a routine health check-up (group I-hypertension [HT]), 26 age-matched men with only elevated systolic BP (> or = 140 mm Hg) (group II-HT), and 12 age-matched normotensive (NT) men (< 140/90 mm Hg). During an arithmetic test, group I-HT showed a significantly higher increment of systolic BP (+14.5-18.0%) than group II-HT (+9.3-10.2%) and NT controls (+6.4-8.2%). However, no significant difference in BP response was seen between group II-HT and NT controls. Plasma norepinephrine in group I-HT showed a significant increase after the test, (171 +/- 23-->202 +/- 27 pg/mL), whereas group II-HT and NT controls showed no change. No significant difference occurred in epinephrine response among the three groups. These results suggest that the young male subjects with screening BP above 140/90 mm Hg are hyperreactive to a mental stress as compared with subjects with only elevated systolic BP or NT controls.

Diagnostica--a Bayesian decision-aid system--applied to hypertension diagnosis.

"Diagnostica" is a Bayesian statistical tool designed to collect and store the patient's data, suggest a diagnosis, and explain the decision in terms of density distributions. The program is written in C language on MacIntosh support. It is described using the case study of differential diagnosis between essential and secondary hypertensions (i.e., fibrodysplastic renal artery stenosis, atheromatous renal artery stenosis, Conn's syndrome, nephropathy and pheochromocytoma). Seventeen experimental parameters were taken into consideration, all of them available during the first medical examination. The density distributions of all items were established from the ARTEMIS experimental database. Both a priori probabilities of different types of hypertension and loss coefficients are taken into account in the calculations. Diagnostica can be used in a "make diagnosis" mode or in an "edition" mode. In the first case it can serve a physician in everyday practice; in the second it becomes a tool for medical research.

On the Mechanisms and Clinical Relevance of One-Kidney, One-Clip Hypertension

Dr. Skeggs demonstrated the lack of renin dependence in 1-kidney, 1-clip hypertension and elucidated some of the differences between that and Dr. Goldblatt's classic 2-kidney, 1-clip model of hypertension. Studies of these two different types of hypertension have led research in many new directions and helped to reveal the role of the renin-angiotensin system in hypertension and that system's interaction with sodium-induced vasodilation in both animals and humans. More recent research has investigated the processes behind essential hypertension and I present here the proposal that, due to nephron heterogeneity, essential hypertension in humans is parallel in its pathophysiologic processes to Goldblatt hypertension.

Normoprolactinaemia in spontaneously hypertensive rats: absence of a close relationship between plasma concentrations of prolactin and systolic blood pressure

Prolactin has been involved in different types of hypertension both in man and in rats. In an attempt to substantiate this hypothesis, we have analysed the correlation between plasma concentrations of prolactin and systolic blood pressure (SBP) in female and male rats from spontaneously hypertensive (SH) and normotensive Wistar-Kyoto strains (30, 60 and 90 days old), as well as in adult female Wistar rats rendered hyperprolactinaemic by the administration of 100 micrograms testosterone propionate on day 1 of life, or adult males with low plasma concentrations of prolactin after administration of bromocriptine (4 mg/kg per day) over 15 days. Our results indicate a lack of correlation between plasma concentrations of prolactin and SBP since plasma concentrations of prolactin were normal in male and female SH rats and hyper- and hypoprolactinaemia did not affect SBP. In spite of these normal plasma concentrations of prolactin, SH rats showed subtle changes in the secretion of this hormone in vitro and in vivo in response to exogenous serotonin administration and to immobilization.

Zinc, cadmium, and hypertension in parturient women

Zinc deficiency and cadmium toxicity have both been implicated in hypertension during pregnancy. The goals of this study were twofold: first, to assess the different zinc indices (plasma, red blood cell zinc, heat-labile alkaline phosphatase, and placental zinc) in normotensive and hypertensive parturients to determine whether they are altered in the different types of hypertension that occur during pregnancy; second, to assess whole-blood cadmium and placental cadmium with regard to hypertension and zinc status. Patients were diagnosed as having chronic hypertension or preeclamptic toxemia and were then further divided into groups on the basis of smoking status. Each patient was matched with a normal control subject based on age, parity, and smoking status. Forty-three hypertensive patients and their matched control subjects were studied. No differences were found in the various zinc indices between chronic hypertensive parturients and normal control subjects. However, in parturients with preeclamptic toxemia, the plasma zinc level was 19% lower than in control subjects (p less than 0.02); these patients had the lowest plasma zinc level of the three groups. Placental zinc was also 12% lower in patients with preeclamptic toxemia than in control subjects (p less than 0.04). Whole-blood cadmium and placental cadmium levels did not differ between control subjects or hypertensive patients. However, a significant positive correlation was found between whole-blood cadmium and plasma zinc levels in preeclamptic toxemia (r = 0.53; p less than 0.05). The results support a marginal zinc deficiency in parturients with preeclamptic toxemia but not in those with chronic hypertension. The role of cadmium in the cause of preeclamptic toxemia remains unclear.

Calcium metabolism in the pathophysiology and treatment of clinical hypertension.

Two parallel lines of research increasingly implicate calcium in the pathophysiology of hypertension. Studies at the molecular-cellular level reveal that, as part of a second messenger system, calcium plays a critical role in cellular responses that are of special relevance to blood pressure homeostasis. Investigations at the epidemiological and clinical levels have also increasingly involved calcium in hypertension, although the data produced are often contradictory, suggesting alternately that hypertension involves excess calcium and that the disorder is associated with a calcium deficiency. In our own research, which emphasizes both the biochemical and the clinical heterogeneity of the hypertensive process, we have found that divalent cation metabolism may be shifted in both directions away from average normotensive values among different types of hypertension. In addition, these calcium metabolic shifts appear to mediate the pressor effects of salt in both human and experimental forms of hypertension and may help identify individuals for whom different therapeutic regimens would be appropriate. We have developed a working cellular hypothesis in which all forms of hypertension are seen as calcium-dependent. One form is more critically dependent on extracellular calcium and is characterized by low plasma renin activity, dietary salt sensitivity, and therapeutic responsiveness to oral calcium supplementation and to calcium-channel blockade. At the opposite extreme, the intracellular calcium-dependent, angiotensin II-mediated form is characterized by high renin, lack of salt sensitivity, and preferential response to beta-blockade and converting-enzyme inhibition.

Hypertension as related to renal function in diabetes mellitus.

The relationships between blood pressure and renal function were investigated in 78 hypertensive patients with diabetes mellitus type I or II. Renal function was assessed by determining the glomerular filtration rate and the para-aminohippurate clearance in 32 and serum creatinine in 46 subjects. In the latter, the reciprocal serum creatinine, corrected for age and changing creatinine/insulin clearance ratio, was used as an estimate of glomerular filtration rate. In the 54 patients with serial determinations, the duration of follow-up averaged 10.5 years. In older patients with type II diabetes without clinical proteinuria, hypertension developed either before or after the onset of diabetes. When it appeared, renal function was only slightly reduced. During follow-up, the decline in reciprocal serum creatinine averaged 2.7% per year, a figure very similar to that found in nondiabetic patients with benign essential hypertension. It did not correlate with the blood pressure. In patients with a proteinuria greater than 2.5 g per day and histologic and/or clinical evidence of diabetic glomerulosclerosis, the severity of hypertension correlated inversely with the level of renal function. The rate of decline in function averaged 11% per year but varied widely. It was not significantly related to the blood pressure. These data suggest that different types of hypertension (essential, diabetic, and nephrogenic) may be associated with diabetes mellitus. The rate of decline in renal function is closely related to the presence or absence of clinical proteinuria but not to the level of blood pressure.

Autonomic innervation of cerebral blood vessels decreases in renal hypertensive rats.

The ultrastructural distribution of the autonomic nerves of brain arteries was investigated in renal (one-kidney, one clip) hypertensive and normotensive Wistar-Kyoto rats. Sympathetic and nonsympathetic nerve terminals were found only in the adventitial layer of brain arteries of renal hypertensive and normotensive rats. In both normotensive and renal hypertensive rats the total nerve endings were dense in anterior cerebral artery, moderately dense in middle cerebral artery, and sparse in basilar artery. In normotensive rats, nonsympathetic nerves outnumbered sympathetic nerves in anterior cerebral, middle cerebral, and basilar arteries. In renal hypertensive rats these two types of nerve terminals in close apposition to smooth muscle decreased in anterior cerebral and basilar arteries, while those in middle cerebral arteries remained unchanged. These results suggest that the potential neurogenic control of cerebral blood vessels as well as the trophic effect of sympathetic nerves on brain blood vessels may decrease in renal hypertensive rats. As this finding contrasts with that in spontaneously hypertensive rats, the pattern of innervation in brain arteries may differ in different types of hypertension.