Renal receptors in the rat sensitive to chemical alterations of their environment.

Abstract

SUMMARY Two major groups of renal chemosensory neural elements have been identified in the rat: one specifically activated by renal ischemia, the previously described "R" chemoreceptors, and the other by backflow of nondiuretic urine into the renal pelvis. The latter group is the object of the present investigation. In anesthetized, male Sprague-Dawley rats, single-unit recordings were obtained by dissection of the centrally cut nerves of the right kidney. The responses of single units to backflow into the renal pelvis of nondiuretic urine, diuretic urine, and solutions containing urea, mannitol, or inorganic ions were compared. The excitatory effect of the backflow of nondiuretic urine was due to its chemical composition rather than to changes in pelvic pressure and pelvic distension. The same units were activated markedly by renal ischemia. The resting discharge rate of the units was very high in nondiuretic conditions, and it declined progressively when diuresis was induced by expansion of the extracellular fluid volume. It is concluded that this group of sensory elements responds to the chemical environment in the renal interstitium as modified by ions crossing the pelvic epithelium, by leakage of ions out of ischemic cells, and by alterations in the excretory function of the kidney and renal blood flow. This group of renal sensory nerve endings has been termed "R2" chemoceptive receptors, to distinguish them from the previously described group of renal "R" chemoreceptors. Circ Res 46: 395-405, 1980LIKE OTHER visceral organs, the kidneys have a profuse sensory innervation. From recordings of impulses conducted along afferent fibers in the renal nerves, several functional classes of renal sensory receptors have been identified so far. In cats, there are receptors sensitive to alterations in ureteral pressure and to venous or arterial perfusion pressure (Beacham and Kunze, 1969;Astrom and Crafoord, 1968); in rabbits, receptors affected by changes in ureteral and arterial perfusion pressure, but not changes in venous pressure (Niijima, 1971); in dogs, units responsive to changes in venous, ureteral, or arterial perfusion pressure (Uchida et al., 1971); in rats, receptors sensitive to increase in venous pressure (Astrom and Crafoord, 1967). In the renal nerves of the rat at least two other populations exist. The fibers of one group are silent under control conditions and are activated only by renal ischemia; those of the other population exhibit a resting discharge and respond markedly to backflow of urine into the renal pelvis (Recordati et al., 1978 characteristics of the first group of receptors which, because of their sensitivity to ischemia and unresponsiveness to mechanical stimuli, were termed renal, "R," chemoreceptors. The second group, on the other hand, was analyzed only superficially. They were considered to be a population of renal mechanoreceptors because previous investigators (Beacham and Kunze, 1969;Astrom and Crafoord, 1968;Niijima, 1971) had thought that changes in pelvic pressure and pelvic d...

Roles of central renin-angiotensin system and afferent renal nerve in the control of systemic hemodynamics in rats

“…[11][12][13][14]31 The reason for the discrepancy between our result and other studies is not clear. However, the present study also showed that blood pressure and RSNA were consistently increased in response to elevated pelvic pressure in the contralaterally nephrectomized rats.…”

“…It has been considered that the ARN activity is increased by stimulation of the sensory receptors in the kidney. And as the sensory receptors near the pelvic wall are distinctively sensitized to changes in the pelvic pressure [11][12][13] or backflow of the urine into the pelvis, 14 elevation of the pelvic pressure has been a useful tool to activate ARNs. [11][12][13] …”

Renal denervation improves cardiac function in rats with chronic heart failure: Effects on expression of β-adrenoceptors

“…Stimulation of afferent renal nerves has been shown to evoke alterations in sympathetic nerve activity and arterial blood pressure (31,44). The excitatory influence may represent an activation of quiescent renal afferents in response to a variety of stimuli (35,36). There are multiple triggers in the HF condition that have the potential for increased activation of the renal afferent nerve activity, including reduced perfusion pressure, increased venous pressure, increased inflammation, and increased oxidative stress to name a few (18).…”

Afferent renal nerve-dependent hypertension following acute renal artery stenosis in the conscious rat.

“…Similar conflicting evidence exists for other species (Aars and Akre, 1970;Ueda et al, 1967b;Beacham and Kunze, 1969;Calaresu et al, 1976Calaresu et al, , 1978. Such variations may, in part, reflect stimulation of mixed afferent popula-tions, since there is now clear evidence that the renal nerves contain a heterogeneous group of mechanoand chemoreceptor afferent fibers (Calaresu et al, 1978;Recordati et al, 1980).…”