Oropharyngeal regulation of urine output and cardiovascular function in rats with osmotic stimulation by sham ingestion

Abstract

Studies indicate that oropharyngeal afferents participate in the central regulation of hydration status although the role of these afferents in the rat remains controversial. Therefore, we tested the renal effects of oropharyngeal stimulation with water, isotonic saline, and 3% hypertonic saline. We repeated these experiments in oropharyngeal nerve lesioned rats. Anesthetized rats were implanted with femoral catheters, esophageal fistulae, and bladder catheters. During the experiment, each rat was infused with isotonic saline (55 ml/min, iv) containing ketamine (1 mg/kg/min) and xylazine (20 mg/kg/min). After a 1 h baseline, rats were infused orally (1 ml/min; 2 min.) with either 0.9% isotonic saline (n=8), water (n=8), or 3% hypertonic saline (n=6) and urine was collected in 10 min. aliquots for 1 h. Intact animals infused with water produced an early natriuresis and delayed dieresis. Infusions of isotonic saline had no effect. Infusions of 3% hypertonic solution produced an antidiuresis that was concurrent with a natriuresis. Removal of the oralpharyngeal nerves abolished the responses to water and hypertonic saline. The renal effects of oropharyngeal water infusion are consistent with an osmotically‐driven regulation of AVP release. Further, the oralpharyngeal nerves may serve as an anticipatory reflex to perceived ingestion of a volume that will dilute or concentrate plasma osmolality. R01 HL062576.