Ingestion in Fetal Sheep and Its Relation to Sleep States and Breathing Movements

Harding, Richard; Sigger, J. N.; Poore, E.R.; Johnson, P

doi:10.1113/expphysiol.1984.sp002834

Cited by 54 publications

(35 citation statements)

References 16 publications

(29 reference statements)

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“…Absorption of digoxin by the fetus from amniotic fluid could occur by swallowing. However, fetal swallowing does not occur continuously, and intervals between swallowing have been reported to be as long as 2.31 h (20). Given the improbability that each fetus swallowed at the beginning of our study, swallowing is unlikely to be the only mechanism of digoxin absorption by the fetus from amniotic fluid.…”

Section: Discussionmentioning

confidence: 90%

Fetal Uptake of Intraamniotic Digoxin in Sheep

et al. 1990

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ABSTRACT. To explore the possibility that intraamniotic is impractical to treat tachyarrhythmia both because multiple administration of digoxin is an effective treatment regimen intrafetal injections are required and because fetal plasma digoxin for fetal tachyarrhythmia, we injected digoxin into the concentrations are difficult to control. To determine whether amniotic fluid cavity of pregnant sheep and examined the intraamniotic administration of digoxin might effectively treat time course of digoxin distribution to the fetal and maternal fetal tachyarrhythmia, we injected digoxin into the amniotic plasma compartments. Animals were studied in two groups cavity of pregnant sheep and measured the distribution of digoxin according to digoxin dosage: 0.7-1.8 nmol/kg fetal body wt from the amniotic cavity to the fetal and maternal plasma in the high-dose group (n = 6) and 0.1-0.6 nmol/kg fetal compartments. body wt in the low-dose group (n = 14). Within 1 h, plasma digoxin concentrations in the high-dose and low-dose L, and at 24 h they were 2.3 nmol/L (n = 1) and 1.8 f 1.2 gestation. Surgical techniques to implant catheters into the ewe nmol/L, respectively. Peak maternal digoxin levels were and the fetus have been described in detail previously (14). about one-tenth fetal values in the high-dose group and Briefly, after spinal anesthesia was induced in the ewe with 4 mL undetectable in the low-dose group. Fetal digoxin concen-of 1 % tetracaine hydrochloride, polyvinyl catheters were inserted trations were significantly greater in the descending aorta into a peripheral artery and vein. The ewes were given an i.v.than in the umbilical vein ( p < 0.02). Fetal arterial blood infusion of 0.9% saline during the operative procedure. Ketamine pressure and heart rate were not significantly different was administered intravenously in doses of 100 mg every 15-20 from control at any time after digoxin administration. min. Through a midline incision, the uterus was exposed and These results demonstrate that digoxin is rapidly taken up the fetal hindlimbs identified. Polyvinyl catheters were inserted into the fetal circulation from the maternal amniotic cavity. into a peripheral artery and vein of each hindlimb and advanced The exact mechanism whereby this occurs is unknown, but to the descending aorta and inferior vena cava. In seven fetuses, transplacental transfer from the maternal circulation is not an 8 F polyvinyl catheter was inserted suprapubically into the involved. Our findings suggest that intraamniotic admin-urinary bladder through a purse-string suture (15). A 3.5 F istration of digoxin may be an alternative treatment for multiple side-hole catheter was introduced into a distal cotylefetal tachyarrhythmias when direct administration of an-donary tributary of the umbilical vein and advanced proximally tiarrhythmic agents is ineffective or produces maternal toward the fetal body in 12 animals. Two catheters were also toxicity. (Pediatu Res 27: 282-285, 1990) inserted into the amniotic cavity, one near the cervix a...

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Section: Discussionmentioning

confidence: 90%

Fetal Uptake of Intraamniotic Digoxin in Sheep

et al. 1990

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“…Previous studies also have demonstrated that fetal swallowing activity occurred in association with electrocortical activity and that alterations in fetal electrocortical activity may affect fetal swallowing by using intravenous injection of cholinergic antagonist atropine sulfate passing the blood-brain barrier vs. atropine methyl nitrate acting peripherally only in fetal sheep (28). Because fetal swallowing occurs predominantly during LV ECoG periods (14), change of the relative duration of LV periods may influence the swallowing rate. Although there was a small percentage of intermediate ECoG status in the fetus, which was not changed following the treatment.…”

Section: Discussionmentioning

confidence: 99%

“…Fetal swallowing may be regulated by multiple factors, including dipsogenic stimulation, appetite, amniotic fluid availability, and behavioral status (3,14,21). In the present study, we used c-fos mapping technique to determine fetal central nervous activity that correlated to stimulated swallowing responses.…”

Section: Discussionmentioning

confidence: 99%

Central cholinergic mechanisms mediate swallowing, renal excretion, and c-fos expression in the ovine fetus near term

Shi

Mao²,

Zeng³

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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mechanisms mediate swallowing, renal excretion, and c-fos expression in the ovine fetus near term. Am J Physiol Regul Integr Comp Physiol 296: R318 -R325, 2009. First published September 10, 2008 doi:10.1152/ajpregu.90632.2008.-Fetal swallowing and renal metabolism contribute importantly to amniotic and body fluid homeostasis. To determine central cholinergic modulation of swallowing activity and renal excretion associated with neural activity, we examined the effects of intracerebroventricular injection of carbachol, a cholinergic agonist, in ovine fetuses at 0.9 gestation. Fetuses were chronically prepared with thyrohyoid, nuchal and thoracic esophagus, and diaphragm electromyogram electrodes, as well as lateral ventricle and vascular catheters. Electrodes were also implanted on the parietal dura for determination of fetal electrocorticogram (ECoG). After 5 days of recovery, fetal swallowing, ECoG, and urine output were monitored during basal period and the experimental period following intracerebroventricular injection of 0.9% NaCl as the control (n ϭ 5) or carbachol (3 g/kg, n ϭ 5). Central carbachol did not significantly change fetal low voltage (LV) and high voltage (HV) ECoG temporal distributions. However, swallowing activity during LV ECoG was elevated significantly after intracerebroventricular carbachol. Associated with the swallowing activation, c-fos immunoreactivity in the putative dipsogenic center, subfornical organ, was enhanced significantly. The fetal urine flow rate and renal Na ϩ , K ϩ , and Cl Ϫ excretion were markedly increased following intracerebroventricular carbachol and sustained at the high level for at least 2 h. The results indicate that the central cholinergic mechanism is established and functional in regulation of fetal behavior and renal excretion at least at 0.9 gestation, which plays an important role in maintenance of fetal body fluid homeostasis.fetus; carbachol; thirst STIMULATED WATER INTAKE, IN concert with renal water and electrolyte excretion, is the fundamental physiological mechanism that maintains body fluid homeostasis. It is well established that in adult animals, central cholinergic mechanisms play an important role in the control of cardiovascular and body fluid homeostasis (12,15). Central application of cholinergic agonist, carbachol, elicits a variety of physiological responses, including natriuetic, dipsogenic, and pressor responses, as well as vasopressin secretion (2,23,44). Our recent studies demonstrated that intracerebroventricular injection of carbachol also produced pressor responses (42) in the ovine fetus near term, indicating that the central cholinergic mechanism-mediated cardiovascular regulation is functional before birth. However, the role of central cholinergic mechanisms in fetal fluid balance and renal excretion is largely unknown.Progress has been made in demonstrating that swallowing activity can be regulated by hyperosmotic, hypovolemic, and other stimuli such as ANG II and neuropeptide Y in late gestation (31,33,48,49). Fetal renal flu...

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“…However, the fetus can decrease metabolic requirements by reducing both the incidence and amplitude of breathing movements (Fowden et al 1989). These have been associated with a lower rate of lung liquid secretion and occurrence of fetal swallowing (Harding et al 1984;Moessinger et al 1990). Changes in fetal glucose homeostasis not only influence plasma concentrations of insulin (Bassett & Madill, 1974) but also concentrations of IGF.…”

Section: Maternal Nutrition and Fetal Growthmentioning

confidence: 99%