It is well established that renal sympathetic nerves are primarily involved in renal sodium and water regulation. However, the relationship between renal sympathetic nerve activity (RSNA) and renal potassium handling is not extensively known. The present study was performed to investigate the role of the renal sympathetic nervous system in the regulation of tubular potassium reabsorption and secretion.
BACKGROUND: Renal sympathetic innervation plays an important role in the control of renal hemodynamics and may therefore contribute to the pathophysiology of many disease states affecting the kidney. Thus, the present study aimed to investigate the role of the renal sympathetic nervous system in the early deteriorations of renal hemodynamics and structure in rats with pathophysiological states of renal impairment.
METHODS: Anesthetized Sprague Dawley (SD) rats with cisplatin-induced acute renal failure (ARF) or streptozotocin (STZ)-induced diabetes mellitus (DM) were subjected to a renal hemodynamic study 7 days after cisplatin and STZ administration. During the acute study, renal nerves were electrically stimulated, and responses in renal blood flow (RBF) and renal vascular resistance (RVR) were recorded in the presence and absence of renal denervation. Post mortem kidney collection was performed for histopathological assessment.
RESULTS: In innervated ARF or DM rats, renal nerve stimulation produced significantly lower (all p<0.05, vs. innervated control) renal vasoconstrictor responses. These responses were markedly abolished when renal denervation was performed (all p<0.05); however, they appeared significantly higher compared with denervated controls (all p<0.05). Kidney injury was suppressed in denervated ARF, while, irrespective of renal denervation, renal specimens from DM rats were comparable to controls.
CONCLUSIONS: Renal sympathoexcitation is involved in the pathogenesis of the renal impairment accompanying ARF and DM, and may even precede the establishment of an observable renal injury. There is a possible enhancement in the renal sensitivity to intrarenal norepinephrine following renal denervation in ARF and DM rats.
Behavioural assessment of experimental pain is an essential method for analysing and measuring pain levels. Rodent models, which are widely used in behavioural tests, are often subject to external forces and stressful manipulations that cause variability of the parameters measured during the experiment. Therefore, these parameters may be inappropriate as indicators of pain. In this article, a stepping-force analgesimeter was designed to investigate the variations in the stepping force of rats in response to pain induction. The proposed apparatus incorporates new features, namely an infrared charge-coupled device (CCD) camera and a data acquisition system. The camera was able to capture the locomotion of the rats and synchronise the stepping force concurrently so that each step could be identified. Inter-day and intra-day precision and accuracy of each channel (there were a total of eight channels in the analgesimeter and each channel was connected to one load cell and one amplifier) were studied using different standard load weights. The validation studies for each channel also showed convincing results whereby intra-day and inter-day precision were less than 1% and accuracy was 99.36-100.36%. Consequently, an in vivo test was carried out using 16 rats (eight females and eight males). The rats were allowed to randomly walk across the sensor tunnel (the area that contained eight channels) and the stepping force and locomotion were recorded. A non-expert, but from a related research domain, was asked to differentiate the peaks of the front and hind paw, respectively. The results showed that of the total movement generated by the rats, 50.27 ± 3.90% in the case of the male rats and 62.20 ± 6.12% in that of the female rats had more than two peaks, a finding which does not substantiate the assumptions made in previous studies. This study also showed that there was a need to use the video display frame to distinguish between the front and hind paws in the case of 48.80 ± 4.01% of the male rats and 66.76 ± 5.35% of the female rats. Evidently the assumption held by current researchers regarding stepping force measurement is not realistic in terms of application, and as this study has shown, the use of a video display frame is essential for the identification of the front and hind paws through the peak signals.
Regulation of renal function and haemodynamics are under a direct control from the renal sympathetic nerves and renal denervation produces overt diuresis and natriuresis in several mammalian species. However, the inter-related series of changes in renal function and haemodynamics following acute renal denervation (ARD) is not fully understood. Thus, we aimed to investigate and relate the changes in renal function and haemodynamics following acute unilateral renal denervation in anaesthetized Sprague Dawley (SD) rats.