Pharmacological evidence for rapid destruction of efferent renal nerves in rats by intrarenal infusion of 6-hydroxydopamine.

In a previous study we reported that intrarenal (i.r.) infusion of 1 mg 6-hydroxydopamine (6-OHDA) in rats resulted in selective efferent denervation of the infused kidney. Although the vasoconstrictor response to electrical stimulation of the posterior hypothalamus (PH) was already abolished 24 h after infusion, norepinephrine (NE) content of the kidney was reduced by only approximately 50% at that time. In the present study, the status of renal nerves 45 min after infusion of 6-OHDA by i.r. application of scorpion venom (SV), a NE releasing agent, was investigated. In saline pretreated rats, 10 micrograms SV i.r. caused a rapid increase (+355 +/- 80%) in vascular resistance in the injected kidney, whereas only minor changes were observed in resistances of the non-injected kidney, mesentery and hindquarters. Pretreatment of animals with phentolamine (1 mg/kg i.v.) largely abolished the vasoconstrictor response (+57 +/- 20%), confirming dependence of the effect of SV on release of NE from nerve terminals. Finally, pretreatment with 1 mg 6-OHDA i.r. also resulted in abolition of renal vasoconstriction following SV (+7 +/- 6%). The results indicate that as early as 45 min after i.r. infusion of 1 mg 6-OHDA in rats, efferent renal nerve endings are no longer functional.