Plasma osmolality dipsogenic thresholds and c-fos expression in the near-term ovine fetus

Z. Xu, Mark J Nijland, M. G. Ross

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

In ovine and human pregnancy, fetal swallowing contributes importantly to amniotic fluid homeostasis. Fetal dipsogenic responsiveness to short-term plasma hyperosmolality develops in late gestation, although fetal swallowing is not stimulated in response to long-term plasma osmolality increases (2 to 3%), which typically stimulate adult drinking behavior. To explore the near-term fetal plasma osmolality threshold for swallowing stimulation, we examined the effects of i.v. hypertonic saline-induced subacute increases in plasma hypertonicity on fetal swallowing behavior. Central sites of activation were examined by c-fos expression in putative dipsogenic nuclei. The results demonstrate that subacute 2 to 3% plasma osmolality increases do not stimulate near-term ovine fetal swallowing. However, fetal swallowing activity significantly increased (3 times) after plasma osmolality increased >6% above basal values. Consistent with a specific dipsogenic response, i.v. hypertonic saline induced c-fos expression in the anterior third ventricle region, a putative dipsogenic center, as well as in the fetal hindbrain. The stimulation of fetal swallowing under conditions of higher osmotic stimulation and the correlation with forebrain c-fos expression indicates that near-term fetal osmoregulation mechanisms are functional, although not completely mature. Reduced fetal dipsogenic responsiveness may result from altered osmoreceptor sensitivity, downstream neuronal or synaptic immaturity, or potentially inhibitory actions of stimulated hindbrain nuclei.

Original languageEnglish (US)
Pages (from-to)678-685
Number of pages8
JournalPediatric Research
Volume49
Issue number5
StatePublished - 2001
Externally publishedYes

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Deglutition
Osmolar Concentration
Sheep
Fetus
Rhombencephalon
Osmoregulation
Fetal Movement
Pregnancy
Drinking Behavior
Third Ventricle
Amniotic Fluid
Prosencephalon
Homeostasis

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health

Cite this

Plasma osmolality dipsogenic thresholds and c-fos expression in the near-term ovine fetus. / Xu, Z.; Nijland, Mark J; Ross, M. G.

In: Pediatric Research, Vol. 49, No. 5, 2001, p. 678-685.

Research output: Contribution to journalArticle

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