The overall objective of the proposed research is to further characterize the role of the renal nerves in the renorenal reflex responses to renal mechano (MR) and chemoreceptor (CR) stimulation in rats and cats. Furthermore the interaction between the neural and non-neural mechanisms in the control of renin secretion rate (RSR) will be explored in dogs and rats. Nine specific aims will be pursued; 1. and 2. determine the renal functional and electrophysiological changes produced by MR and CR stimulation during various sodium diet. The contralateral changes in urine flow rate (V) and urinary sodium excretion (UNaV) produced by MR and CR stimulation will be related to the ipsilateral and contralateral changes in renal nerve activity (RNA) in rats on low, normal and high sodium diet; 3. determine if the reno renal reflex responses are mediated by activation of renal receptors in the papilla. The contralateral renal responses (functional and electrophysiological) to MR and CR stimulation will be determined before and during ureteropelvic administration of lidocaine; 4. determine the level of integration of the renorenal reflex responses to MR and CR stimulation. The contralateral renal responses to MR and CR stimulation will be determined in rats in which the spinal cord has been sectioned at T6; 5. determine the role of the renal nerves in the contralateral responses to acute and chronic ureteral ligation. In conscious rats the contralateral changes in V and UNaV to ureteral ligation will be followed from time 0 to 48 hrs. after ligation; 6. determine the renorenal reflex responses to MR and CR stimulation in the cat. The effects in contralateral renal blood flow (RBF), V, UNa V and RSR of MR and CR stimulation will be related to those on RNA in cats. 7. and 8. determine the interaction between neural and baroreceptor mechanisms in controlling RSR in rats and dogs with various efferent RNA. The effect of lowering arterial pressure (RAP) to 90 mmHg on RSR will be determined in conscious rats on low and normal sodium diet and in anesthetized dogs before and after non-hypotensive hemorrhage; 9. determine the interaction between epinephrine, neural and baroreceptor mechanisms in controlling RSR. The effect of epinephrine (i.r.a.) on RSR response to lowering RAP to 90 mmHG will be determined in innervated and denervated kidneys.