Renal nerves and catecholamine excretion.

To determine which neurotransmitters are released into urine by renal nerves, we either acutely denervated one kidney or stimulated renal nerves by activation of the baroreflex. Acute denervation increased dopamine (DA) and decreased norepinephrine (NE) excretion from the denervated kidney. In contrast, DA excretion decreased and NE excretion increased progressively from the contralateral innervated kidney. Sodium excretion related directly to DA and inversely to NE excretion. In chronic denervation experiments, baroreceptor stimulation increased NE excretion by 25% more from the innervated kidney than from its contralateral denervated mate, while DA excretion increased by 50% only from the innervated kidney. Baroreflex-stimulated NE and DA excretion from innervated kidneys was reduced by prior feeding of a low salt diet. The response was completely abolished by a high salt diet. Sodium excretion increased by the same proportion from innervated and chronically denervated kidneys following baroreceptor stimulation. In conclusion, 1) renal nerves release both NE and DA, 2) after acute unilateral denervation sodium excretion related directly with DA and inversely with NE excretion, and 3) urinary excretion of NE and DA derived from renal nerves was influenced by dietary sodium intake.