Afferent vagal control of renin release in the anesthetized cat

In the anesthetized, moderately fluid-depleted cat (no fluid infusion during the experiment), bilateral cervical vagotomy caused a marked and prompt increase in renin release from the innervated kidney without significantly affecting renin release from the contralateral denervated kidney. This excitatory effect was a transient one, however, and disappeared 15-30 minutes after vagotomy. The renin-releasing action of vagotomy was antagonized by moderate fluid expansion with 2% dextran in saline (6 ml/kg per hr). Reflex renin release from the innervated kidney was also induced by head-up tilting lasting for 10 minutes, and this reflex response was prevented or markedly weakened by previous cervical vagotomy. It is concluded that receptors connected with vagal fibers exert a tonic restraining influence on renin release, and that suppression of this reflex inhibition by tilting or vagotomy leads to a sympathetically mediated increase in renin release. However, this effect can be promptly compensated by other influences, and can be overcome by intrarenal or humoral mechanisms of renin control.