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S Genovesi

Publications and source records attributed to S Genovesi.

29 records · Page 2Linked to original sources
PubMed1984

Regulation of sodium and water excretions by neural renorenal reflexes in the cat.

The reduction in sodium and water excretion observed in the right kidney when the left kidney is subjected to transient denervation, is entirely abolished by bilateral section of the dorsal roots from T9 to L4, whereas section of the left dorsal roots only, at the same spinal level, does not affect the contralateral renal response to left renal nerve cooling. The possibility that the bilateral dorsal roots section abolished the response of the right kidney because the afferent fibres from the left kidney travel in the right dorsal roots was explored in the present study. Experiments were performed in anaesthetized cats in which reversible denervation of the left kidney was done by cooling of left renal nerves (for 10 min) after cutting the right dorsal roots from T9 to L4. Cooling of left renal nerves caused a large increase in sodium and water excretion from the left kidney and a prompt decrease in sodium and water excretion from the right kidney. During the cooling period arterial pressure did not change and glomerular filtration rate slightly increased in the left kidney only. The results obtained in this group of animals were not significantly different from those previously observed in sham-operated cats or in cats with section of left dorsal roots only. As the contralateral antidiuretic and antinatriuretic response to renal denervation survives dorsal root section on either side but is prevented by bilateral section, this demonstrates that the inhibitory renal afferent fibres responsible for this renorenal reflex are distributed bilaterally to spinal dorsal roots.

Animals↗
PubMed1983

Do renal afferent fibres modulate the function of the contralateral kidney?

Denervation of one kidney has been shown to induce a prompt decrease in sodium and water excretion from the contralateral kidney. The present study was designed to clarify whether this response is due to suppression of a tonic inhibitory renorenal reflex. Experiments were performed in anaesthetized cats in which the renal nerves of the left kidney were transiently blocked by cooling and the effects of this blockade on either kidney were studied in three different groups of animals. The decrease in sodium and water excretion from the contralateral (right) kidney observed in the sham-operated group (intact dorsal roots) was still present, and substantially unchanged, in the second group of animals in which the ipsilateral (left) dorsal roots from T9 to L4 were cut. In the third group of cats, bilateral dorsal root section entirely abolished the response of the contralateral kidney to renal nerve cooling. These experiments demonstrate that the contralateral decrease in sodium and water excretion is due to the block of afferent renal nerve fibres which project bilaterally to the spinal cord.

Afferent Pathways↗
PubMed1982

Renorenal reflexes in the rat elicited upon stimulation of renal chemoreceptors.

The effects of renal ischemia and backflow of non-diuretic urine into the renal pelvis on renal efferent sympathetic postganglionic nerve activity, femoral arterial pressure and heart rate were studied to verify whether stimulation of renal chemoreceptors elicits autonomic reflexes. In rats with intact spinal cord or spinal cord sectioned at the T6 level a brief activation of renal chemoreceptors produced excitatory ipsilateral and contralateral renorenal reflexes, whereas it only slightly and insignificantly altered arterial pressure and heart rate. These results indicate that stimulation of renal chemoreceptors elicits renorenal excitatory reflexes which might be integrated both at spinal and supraspinal levels.

Adrenergic Fibers↗
PubMed1981

Renal chemoreceptors.

A study of the renal receptors and types of stimuli which give origin to supraspinal and spinal-mediated autonomic reflexes is presented. Multiunit and single unit recordings from the afferent renal nerves of male Sprague-Dawley rats have revealed two groups of renal chemosensitive receptors (chemoreceptors). These we have called renal R1 and R2 "chemoceptive" receptors. R1 receptors do not have a resting discharge but are activated after 38.7 +/- 3.3 (S.E) sec (n = 40) of complete renal ischemia (occlusion of the renal artery). Other activating stimuli are associated with a marked impairment in renal blood flow (prolonged occlusion of the renal vein and the hypotension of systemic asphyxia or hemorrhage). Their discharge is characterized by trains of impulses which cease abruptly upon re-entry of blood into the kidney. They are not responsive to increases or decreases in renal perfusion pressure or to increases in renal venous or ureteral pressure. In contrast, R2 receptors have a resting discharge and respond vigorously to backflow of normal urine (nondiuretic) into the renal pelvis. The results of the backflow into the pelvis of different test solutions (diuretic and nondiuretic urine, 1 M urea, 1 M mannitol and solutions of NaCl and KCl) indicate that this response is dependent upon the composition of the fluid bathing the renal pelvis rather than the increase in pelvic pressure or pelvic distension. The resting discharge rate is highest in nondiuretic conditions and declines substantially after diuresis is induced by extracellular volume expansion. R2 receptors are also activated by renal ischemia produced by clamping the renal artery. It is concluded that these two groups of afferent sensory units are renal chemosensitive receptors, (chemoreceptors) which respond to the chemical environment of renal interstitium.

Afferent Pathways↗
PubMed1981

Excitatory effect of converting enzyme inhibitors on efferent sympathetic postganglionic nerve activity to the kidney in the rat.

1. Experiments were designed to evaluate the effect of converting enzyme inhibitors on autonomic nervous system function in the rat. 2. Arterial blood pressure, heart rate, efferent postganglionic sympathetic activity and afferent nerve activity from the right renal nerves were recorded in anaesthetized, spontaneously breathing, non diuretic rats, either with an intact spinal cord or with a spinal cord transected at the T6 level, before, during and after intravenous injections of 0.5--1.0 mg/kg of teprotide or captopril. 3. After injection of drugs, efferent sympathetic nerve activity markedly increased and reached its peak value 4 min later, both in rats with an intact spinal cord (101 +/- 21% mean +/- SE, above the control discharge) and with a spinal cord transected at the T6 level (166 +/- 41%, above the control). 4. Afferent activity from the renal nerve, on the other hand, did not consistently change during converting enzyme blockade. 5. The results indicate that the efferent sympathetic excitation cannot be due either to a baroreceptor or to a renorenal reflex. This excitation might be responsible, at least in part, for the increase in renin secretion which follows the blockade of angiotensin-converting enzyme.

Adrenergic Fibers↗
PubMed1980

Reno-renal and reno-adrenal reflexes in the rat.

1. Experiments were carried out to investigate whether the activation of renal chemoceptive receptors by natural stimuli might induce reflex alterations of efferent postganglionic activity to the ipsilateral kidney and preganglionic activity to the ipsilateral adrenal. 2. In anaesthetized rats with intact nervous system back-flow of urine and occlusion of the renal artery were accompanied by increments in efferent sympathetic activity both to the kidney and adrenal without concomitant changes in heart rate and blood pressure. 3. Greater excitatory responses in nerve activity to the same test stimuli were observed in rats with the spinal cord cut at C 1. 4. These results indicate that the natural activation of renal chemoceptive receptors might induce reno-renal and reno-adrenal excitatory reflexes which are likely to be integrated at spinal and supraspinal levels.

Adrenal Glands↗