Role of the sympathetic nervous system in human renovascular hypertension

The Effects of Renal Nerve Denervation on Blood Pressure and Target Organs in Different Hypertensive Rat Models

Background

Hypertension contributes to the progression of cardiac remodeling and renal damage. In turn, renal sympathetic hyperactivation showed elevated sympathetic nervous system activity and led to blood pressure increase in certain patients. The purpose of this study was to observe the effect of renal nerve denervation on blood pressure and target organ changes in two hypertensive rat models.

Methods

Hypertensive rats were randomly divided into a renal denervation (RDN) group and sham operation group. Wistar–Kyoto (WKY) rats of the same age were set as the baseline control group. In the secondary hypertension model, SD rats were randomly divided into five groups. Blood pressure and bodyweight were measured every week until they were euthanized.

Results

The two rat models underwent RDN at key timepoints. At these timepoints, the hearts and kidneys were collected for norepinephrine and angiotensin II measurements and histological analysis.

Conclusion

RDN performed before development of hypertension showed a significant antihypertensive effect on the secondary hypertension model.

Control of renal sympathetic nerve activity by neurotransmitters in the spinal cord in Goldblatt hypertension

The role of spinal cord neurons in renal sympathoexcitation remains unclear in renovascular hypertension, represented by the 2-kidney, 1-clip (2K1C) model. Thus, we aimed to assess the influence of spinal glutamatergic and AT1 angiotensin II receptors on renal sympathetic nerve activity (rSNA) in 2K1C Wistar rats. Hypertension was induced by clipping the renal artery with a silver clip. After six weeks, a catheter (PE-10) was inserted into the subarachnoid space and advanced to the T10-11 vertebral level in urethane-anaesthetized rats. The effects of intrathecally (i.t.) injected kynurenic acid (KYN) or losartan (Los) on blood pressure (BP) and rSNA were analysed over 2 consecutive hours. KYN induced a significantly larger drop in rSNA among 2K1C rats than among control (CTL) rats (CTL vs. 2K1C: -8 ± 3 vs. -52 ± 9 spikes/s after 120'). Los also evoked a significantly larger drop in rSNA among 2K1C rats than among CTL rats starting at 80' after administration (CTL vs. 2K1C - 80 min: -10 ± 2 vs. -32 ± 6^∗; 100 min: -15 ± 4 vs. -37 ± 9^∗; 120 min: -12 ± 5 vs. -37 ± 8^∗ spikes/s). KYN decreased BP similarly in the CTL and 2K1C groups; however, Los significantly decreased BP in the 2K1C group only. We found upregulation of AT1 gene expression in the T11-12 spinal segments in the 2K1C group but no change in gene expression for AT2 or ionotropic glutamate (NMDA, kainate and AMPA) receptors. Thus, our data show that spinal ionotropic glutamatergic and AT1 receptors contribute to increased rSNA in the 2K1C model, leading to the maintenance of hypertension; however, the participation of spinal AT1 receptors seems to be especially important in the establishment of sympathoexcitation in this model. The origins of those projections, i.e., the brain areas involved in establishing the activity of spinal glutamatergic and angiotensinergic pathways, remain unclear.

Rational use of antihypertensive medications in children

Hypertension has traditionally been regarded as an uncommon diagnosis in childhood and adolescence; however, there is compelling evidence to suggest that its prevalence is on the rise, particularly in those with obesity. As a result, pediatricians increasingly are asked to evaluate and manage patients with elevated blood pressure. An increased emphasis on conducting drug trials in children over the last 15 years has yielded important advances with respect to evidence-based data regarding the efficacy and safety of antihypertensive medications in children and adolescents. Unfortunately, data to definitively guide selection of initial agents is lacking. This article will present guidelines for the appropriate use of antihypertensive medications in the pediatric population, including the rational approach to selecting an appropriate medication with respect to pathophysiology, putative benefit, and likelihood for side effects.