Volume receptors in guinea pig labyrinth: relevance with respect to ADH and Na control

Abstract

We tested the hypothesis that changes in extracellular fluid volume are reflected by pressure changes within structures of the inner ear and that through neural pathways, a control mechanism exerts an influence on antidiuretic hormone (ADH) release and Na excretion. The study was performed on 35 guinea pigs. In protocol 1, 13 animals were studied before and after decompression of the inner ear by bilateral fluid withdrawal in an experimental setting of sustained isotonic expansion that kept the osmoreceptor partially activated and the intrathoracic volume receptors suppressed. A group of six sham-operated animals served as control. In protocol 2, nine animals were studied before and after a unilateral rise in their inner ear pressure during slightly hypertonic low-rate infusions that kept the osmoreceptor and thoracic volume receptors stimulated. A group of seven sham-operated guinea pigs served as controls. Decompression of the inner ear was attended by a rise in plasma ADH from 11.9 +/- 2.4 to 29.1 +/- 6.9 pg/ml, in urine osmolality (Uosmol) from 470 +/- 48 to 712 +/- 46 mosmol/kg (P less than 0.001), and a fall in urine flow rate (V) from 184 +/- 47 to 71 +/- 11 microliters/min (P less than 0.01), whereas plasma Na (PNa) and osmolality (Posmol) did not change. During inner ear hypertension, plasma ADH fell from 25.6 +/- 3.9 to 18.4 +/- 3.1, Uosmol from 829 +/- 58 to 627 +/- 43 (P less than 0.001), and V rose from 51 +/- 11 to 130 +/- 23 (P less than 0.001), whereas glomerular filtration rate, PNa, and Posmol did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

The Endolymphatic Sac: A Scanning and Transmission Electron Microscopy Study

“…Furthermore, pressure changes of the inner ear have been suggested to control ADH release [17]. The intraluminal stainable homogeneous substance has been shown to contain a large amount of hyaluronic acid [18]; however, protein complexes have also been detected [18].…”

Responses of vestibular neurons to arginine vasopressin microinjection

“…Experiments have demonstrated that electrical stimulation of the VIIIth nerve and caloric stimulation of the labyrinth modulate the electrical activity of neurons located in the magnocellular part of the SON and PVN [3] that are responsible for VP release [20]. In addition, pressure changes within the inner ear influence VP plasma levels and Na excretion in acute and anaesthetized guinea-pigs [5] as well as in free-moving animals [33].…”

Distribution of Alpha-ANP in the Cochlea and the Vestibular Organs

“…the fibroblast-like smooth muscle cells in the spiral ligament and the spiral limbus resemble those of the mesangial cells. Recently it has been postulated that pressure changes may control antidiuretic hormone 76 Yoon/Anniko Alpha-ANP in the Labyrinth (ADH) release via a neural pathway, for instance in the inner ear [12]. In the CNS there occurs ANP-containing neurons which act as a neuromodulator or neurotransmit ter [13].…”