AT(2) receptors mediate tonic renal medullary vasoconstriction in renovascular hypertension.

1. Renal medullary blood flow is relatively insensitive to angiotensin II (Ang II)-induced vasoconstriction, due partly to AT(1)-mediated release of nitric oxide and/or prostaglandins. AT(2)-receptor activation appears to blunt AT(1)-mediated vasodilatation within the medullary circulation. This could affect long-term efficacy of antihypertensive pharmacotherapies targeting the renin/angiotensin system, particularly in Ang II-dependent forms of hypertension. 2. We tested the effects of AT(1)- and AT(2)-receptor blockade on basal cortical and medullary laser Doppler flux (CLDF and MLDF), and on responses to renal arterial infusion of Ang II, in rats with 2 kidney, 1 clip (2K1C) hypertension and sham-operated controls. Studies were carried out in thiobutabarbital (175 mg kg(-1), i.p.) anaesthetised rats, 4 weeks after clipping, or sham surgery (n=6 in each of eight groups). 3. Candesartan (10 microg kg(-1) h(-1), intravenous (i.v.)) reduced mean arterial pressure ( approximately 17%) and increased CLDF ( approximately 24%), similarly in both sham and 2K1C rats, but did not significantly affect MLDF. PD123319 (1 mg kg(-1) h(-1), i.v.) increased basal MLDF (19%) in 2K1C but not sham rats, without significantly affecting other variables. 4. In sham rats, renal arterial infusion of Ang II (1-100 ng kg(-1) min(-1)) dose dependently decreased CLDF (up to 44%), but did not significantly affect MLDF. These effects were markedly blunted in 2K1C rats. After PD123319, Ang II dose dependently increased MLDF (up to 38%) in sham but not 2K1C rats. Candesartan abolished all effects of Ang II, including those seen after PD123319. 5. Our data indicate that AT(1) receptors mediate medullary vasodilatation, which is opposed by AT(2)-receptor activation. In 2K1C hypertension, AT(2)-receptor activation tonically constricts the medullary circulation.

Cognitive components of deficit awareness in Alzheimer's disease.

Awareness of deficit was examined in 24 patients with Alzheimer's disease (AD) and their spouses (for a total of 48 participants) using performance prediction-postdiction and questionnaire discrepancy (QD) paradigms. Participants estimated their own memory performances as well the performances of spouses and of a fictional, memory-disordered patient observed on videotape. Patients overpredicted self-performances, but the extent of overestimation decreased for postdictions. Patients and caregivers accurately estimated caregiver performances but overestimated performances of the fictional patient. QD data revealed that patients underestimated their difficulties performing daily functioning tasks as compared with caregiver reports. Awareness of deficit is a complex ability, involving dissociable cognitive processes. AD patients may display intact immediate awareness of memory dysfunction but fail to incorporate incidents of memory failure into generalized self-belief systems.

Attention, learning, and memory performances and intellectual resources in Vietnam veterans: PTSD and no disorder comparisons.

Attention, learning, memory, and estimated intellectual potential were examined in 26 Vietnam veterans diagnosed with posttraumatic stress disorder (PTSD) and in 21 Vietnam veterans without mental disorders. Results revealed PTSD-associated cognitive deficits on tasks of sustained attention, working memory, initial learning, and estimated premorbid intelligence but not on measures of focus of attention, shift of attention, or memory savings. Cognitive task performances adjusted for estimated native intelligence remained negatively correlated with PTSD severity. An intellectual measure adjusted for cognitive task performances was negatively correlated with PTSD severity, even after the authors statistically controlled the level of combat exposure. Results suggested that although intellectual resources may constitute a vulnerability-protective factor for PTSD development, PTSD was associated with cognitive impairment independent of intellectual functioning.

AT2 receptors contribute to acute blood pressure-lowering and vasodilator effects of AT1 receptor antagonism in conscious normotensive but not hypertensive rats.

The aims of this study were to determine the contribution of the AT2 receptor to the antihypertensive and regional vasodilatory effects of AT1 receptor blockade in adult spontaneously hypertensive rats (SHR), 2-kidney, 1-clip hypertensive (2K1C) rats, and sham-operated normotensive rats. Several studies have provided evidence to support the notion that the AT2 receptor may have opposing effects to those mediated by the AT1 receptor. We therefore tested the hypothesis that the depressor and vasodilator effects of acute AT1 receptor blockade are dependent on AT2 receptor activation. Heart rate, mean arterial pressure, and regional hemodynamics were measured over a 4-day protocol in rats that received the following treatments in randomized order: saline vehicle, the AT1 receptor antagonist candesartan (0.1 mg/kg iv bolus), the AT2 receptor antagonist PD-123319 (50 microg.kg(-1).min(-1)), or both antagonists. Intravenous candesartan reduced mean arterial pressure in all groups of rats, and this was accompanied by renal and mesenteric vasodilation. Neither saline nor PD-123319 significantly affected these variables. Concomitant PD-123319 administration partially reversed the depressor and mesenteric vasodilator effects of candesartan in sham-operated normotensive rats but not in SHR or 2K1C rats. These data indicate that the AT2 receptor contributes to the blood pressure-lowering and mesenteric vasodilator effects of AT1 receptor blockade in the acute setting in conscious normotensive but not hypertensive rats.

Cardiovascular status following combined angiotensin-converting enzyme and AT1 receptor inhibition in conscious spontaneously hypertensive rats.

1. Combined treatment of spontaneously hypertensive rats (SHR) with AT1 receptor antagonists and angiotensin-converting enzyme (ACE) inhibitors has been shown to reduce mean arterial pressure (MAP) more than monotherapy with either agent. The aims of the present study were to investigate the effects of chronic dual renin-angiotensin system (RAS) inhibition using non-hypotensive doses of the AT1 receptor antagonist candesartan cilexetil and the ACE inhibitor perindopril on cardiovascular function and structure. 2. Adult male SHR, aged 15 weeks, were divided into four groups: (i) candesartan cilexetil (0.5 mg/kg per day in drinking water); (ii) perindopril (0.3 mg/kg per day in drinking water); (iii) combined treatment (dual RAS inhibition); or (iv) the appropriate vehicle (0.1% ethanol/0.1% polyethylene glycol/1.5 mmol/l sodium bicarbonate dissolved in water for candesartan cilexetil; distilled water for perindopril). Systolic blood pressure was measured weekly using the tail-cuff method and urinary microalbuminuria was measured fortnightly. 3. After 4 weeks, rats were instrumented for intravenous drug administration and measurement of MAP. At this time, the cardiovascular effects of angiotensin (Ang) I and AngII (5-20 ng) and sodium nitroprusside (SNP) and acetylcholine (ACh; 1-5 micro g) were assessed. In addition, left ventricular : bodyweight and media : lumen ratios were determined as indices of cardiac and vascular hypertrophy, respectively. 4. Candesartan cilexetil and perindopril alone had minimal effect on MAP when measured both directly and indirectly, whereas direct MAP was significantly decreased in the combined treatment group (131 +/- 6 mmHg; P < 0.05) compared with the vehicle group (156 +/- 9 mmHg). Pressor responses to AngI were significantly decreased in all groups compared with the vehicle-treated group and pressor responses to AngII were significantly decreased in the candesartan cilexetil-treated (P < 0.01) and combined treatment groups (P < 0.01) compared with the vehicle-treated group. Depressor responses to ACh and SNP were not significantly affected by any of the antihypertensive therapies compared with vehicle-treated SHR. 5. Vascular hypertrophy was significantly decreased in the candesartan cilexetil and combined groups compared with the vehicle-treated group, whereas cardiac hypertrophy was reduced, with the rank order of effect being: dual RAS inhibition > perindopril > candesartan cilexetil. Urinary albumin tended to decrease with dual RAS inhibition, but was not significantly affected by this short-term treatment. 6. These results demonstrate the efficacy of low-dose dual RAS inhibition as an antihypertensive modality, at least in SHR, not only in reducing arterial pressure, but also in improving cardiovascular structure.

Disparate roles of AT2 receptors in the renal cortical and medullary circulations of anesthetized rabbits.

The contributions of angiotensin II type 1 (AT1) and type 2 (AT2) receptors to the control of regional kidney blood flow were determined in pentobarbital-anesthetized rabbits. Intravenous candesartan (AT1 antagonist; 10 microg/kg plus 10 microg x kg(-1) x h(-1)) reduced mean arterial pressure (12%) and increased total renal blood flow (29%) and cortical laser-Doppler flux (18%) but not medullary laser-Doppler flux. Neither intravenous PD123319 (AT2 antagonist; 1 mg/kg plus 1 mg x kg(-1) x h(-1)) nor saline vehicle significantly affected these variables, and the responses to candesartan plus PD123319 were indistinguishable from those of candesartan alone. In vehicle-treated rabbits, renal-arterial infusions of angiotensin II (1 to 25 ng x kg(-1) x min(-1)) and angiotensin III (5 to 125 ng x kg(-1) x min(-1)) dose-dependently reduced renal blood flow (up to 51%) and cortical laser-Doppler flux (up to 50%) but did not significantly affect medullary laser-Doppler flux or arterial pressure. Angiotensin(1-7) (20 to 500 ng x kg(-1) x min(-1)) had similar effects but of lesser magnitude. CGP42112A (20 to 500 ng x kg(-1) x min(-1)) did not significantly affect these variables. After PD123319 administration, angiotensin II and angiotensin III dose-dependently increased medullary laser-Doppler flux (up to 84%), and reductions in renal blood flow in response to angiotensin II were enhanced. Candesartan abolished renal hemodynamic responses to the angiotensin peptides, even when given in combination with PD123319. We conclude that AT2 receptor activation counteracts AT1-mediated vasoconstriction in the renal cortex but also counteracts AT1-mediated vasodilatation in vascular elements controlling medullary perfusion. These mechanisms might have an important effect on the control of medullary perfusion under conditions of activation of the renin-angiotensin system.

Global-local visual processing in posttraumatic stress disorder.

The purpose of this study was to examine a behavioral index of hemispheric asymmetry (i.e., visual hierarchical attention) in posttraumatic stress disorder (PTSD), a disorder characterized by anxiety and other emotional symptoms. A reaction time based, computerized, global-local visual paradigm was administered to 26 PTSD-diagnosed and 22 psychopathology-free right-handed, male Vietnam War zone veterans. Results indicated that PTSD-diagnosed veterans displayed slower reaction times to all targets than the no-mental disorders comparison sample. However, findings also revealed a Group x Target location interaction in which the PTSD group was slower than the no-disorders comparison sample to respond to local, but not global, targets. Moreover, relative global bias was greater among PTSD-diagnosed veterans than their no-diagnosis counterparts. Findings provide partial support for the hypothesis that PTSD may be associated with a functional cerebral asymmetry favoring the right hemisphere.