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Li S, Wang F. Vertebrate Evolution Conserves Hindbrain Circuits despite Diverse Feeding and Breathing Modes. eNeuro 2021; 8:ENEURO.0435-20.2021. [PMID: 33707205 PMCID: PMC8174041 DOI: 10.1523/eneuro.0435-20.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 01/08/2021] [Accepted: 01/12/2021] [Indexed: 12/21/2022] Open
Abstract
Feeding and breathing are two functions vital to the survival of all vertebrate species. Throughout the evolution, vertebrates living in different environments have evolved drastically different modes of feeding and breathing through using diversified orofacial and pharyngeal (oropharyngeal) muscles. The oropharyngeal structures are controlled by hindbrain neural circuits. The developing hindbrain shares strikingly conserved organizations and gene expression patterns across vertebrates, thus begs the question of how a highly conserved hindbrain generates circuits subserving diverse feeding/breathing patterns. In this review, we summarize major modes of feeding and breathing and principles underlying their coordination in many vertebrate species. We provide a hypothesis for the existence of a common hindbrain circuit at the phylotypic embryonic stage controlling oropharyngeal movements that is shared across vertebrate species; and reconfiguration and repurposing of this conserved circuit give rise to more complex behaviors in adult higher vertebrates.
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Affiliation(s)
- Shun Li
- Department of Neurobiology, Duke University, Durham, NC 27710
| | - Fan Wang
- Department of Neurobiology, Duke University, Durham, NC 27710
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2
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Harding C, Cockerill H, Cane C, Law J. Using non-nutritive sucking to support feeding development for premature infants: A commentary on approaches and current practice. J Pediatr Rehabil Med 2018; 11:147-152. [PMID: 29125505 DOI: 10.3233/prm-170442] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Non-nutritive sucking is often used with premature infants by either using a pacifier or an expressed breast nipple to support the introduction and development of early oral feeding. The pattern of non-nutritive sucking is distinct in that it involves two sucks per second in contrast to nutritive sucking which is one suck per second. Although some literature has identified that non-nutritive sucking has some benefit for the premature infant's feeding development, it is not entirely clear why such an approach is helpful as neurologically, activation of non-nutritive and nutritive skills are different. A summary is presented of the main approaches that use non-nutritive sucking with reference to the literature. This paper also considers other factors and beneficial approaches to managing the introduction of infant feeding. These are: the infant's toleration of enteral feeds pre oral trials, overall development and gestational age when introducing oral experiences, developing swallowing skills before sucking, physiological stability, health status, as well as the development and interpretation of infant oral readiness signs and early communication.
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Affiliation(s)
- C Harding
- Division of Language and Communication Sciences, City, University of London, London, UK
| | - H Cockerill
- Evelina Children's Hospital, Guy's and St. Thomas's NHS Trust, London, UK
| | - C Cane
- Starlight Neonatal Unit, Barnet Hospital, Royal Free NHS Foundation Hospitals Trust, London, UK
| | - J Law
- School of Education, Communication and Language Sciences, Newcastle University, Newcastle, UK
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Dingess KA, Valentine CJ, Ollberding NJ, Davidson BS, Woo JG, Summer S, Peng YM, Guerrero ML, Ruiz-Palacios GM, Ran-Ressler RR, McMahon RJ, Brenna JT, Morrow AL. Branched-chain fatty acid composition of human milk and the impact of maternal diet: the Global Exploration of Human Milk (GEHM) Study. Am J Clin Nutr 2017; 105:177-184. [PMID: 27903517 PMCID: PMC5183722 DOI: 10.3945/ajcn.116.132464] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 10/12/2016] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND An understudied component of the diet, branched-chain fatty acids (BCFAs) are distinctive saturated fatty acids that may have an important influence on health. Human-milk fatty acid composition is known to differ worldwide, but comparative data are lacking on BCFAs. OBJECTIVE We tested the hypotheses that concentrations of BCFAs in human milk differ between populations and are associated with maternal diet. DESIGN We surveyed the BCFA composition of samples collected as part of a standardized, prospective study of human-milk composition. Mothers were enrolled from 3 urban populations with differing diets: Cincinnati, Ohio; Shanghai, China; and Mexico City, Mexico. Enrollment was limited to healthy mothers of term singleton infants. We undertook a cross-sectional analysis of milk from all women with samples at postpartum week 4 (n = 359; ∼120 women/site). Fatty acids were extracted from milk by using a modified Bligh-Dyer technique and analyzed by gas chromatography. Statistical analysis was performed by ANOVA and Tobit regression. For Cincinnati mothers, 24-h diet recalls were analyzed in relation to the individual BCFA concentrations measured in milk samples. RESULTS Total BCFAs in milk differed by site, with the highest concentration in Cincinnati followed by Mexico City and Shanghai (mean ± SE: 7.90 ± 0.41, 6.10 ± 0.36, and 4.27 ± 0.25 mg/100 mL, respectively; P < 0.001). Site differences persisted after delivery mode, maternal age, and body mass index were controlled for. The individual concentrations of iso-14:0, iso-16:0, iso-18:0, anteiso-15:0, and anteiso-17:0 also differed between sites. Milk concentrations of iso-14:0 and anteiso-15:0 were associated with maternal intake of dairy; iso-16:0 was associated with maternal intakes of dairy and beef. CONCLUSIONS BCFA concentrations in milk at 4 wk postpartum differed between mothers from Cincinnati, Shanghai, and Mexico City. Variations in human-milk BCFAs are influenced by diet. The impact of BCFAs on infant health warrants investigation.
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Affiliation(s)
- Kelly A Dingess
- The Perinatal Institute, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH
| | - Christina J Valentine
- The Perinatal Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH; .,Mead Johnson Nutrition Inc., Evansville, IN; Divisions of
| | | | - Barbara S Davidson
- The Perinatal Institute, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH
| | | | - Suzanne Summer
- Clinical Translational Research Center, Cincinnati Children’s, Cincinnati, OH
| | | | - M Lourdes Guerrero
- National Institute of Medical Sciences and Nutrition, Mexico City, Mexico; and
| | | | | | | | | | - Ardythe L Morrow
- The Perinatal Institute, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH
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Abstract
Swallowing of amniotic fluid by late gestation fetuses increases when amniotic fluid volume (AFV) is elevated. Our objectives were to quantitatively characterize fetal swallowing when AFV is elevated above normal to polyhydramniotic levels and to explore the mechanisms that mediate these changes. Late gestation fetal sheep were studied under basal conditions and during intra‐amniotic infusion of lactated Ringer's solution. Control AFV averaged 631 ± 214 mL (SE, n = 6), swallowed volume was 299 ± 94 mL/day, and there were 5.7 ± 1.8 bouts/day of rapid swallowing. During intra‐amniotic infusion, AFV (3065 ± 894 mL) and daily swallowed volume (699 ± 148 mL/day) increased (P < 0.05) and the number of bouts reached a maximum of 13.7 ± 2.0 bouts/day when AFV exceeded 1500 mL. Unexpectedly, the volume swallowed per bout (57.3 ± 5.8 mL, n = 102) did not vary with AFV (r = 0.023, P = 0.81). Neither the number of swallows/day nor the volume/swallow changed consistently with elevated AFV. Daily swallowed volume increases and reaches a maximum of twice normal as AFV approaches polyhydramniotic levels. Mechanistically, the increase in swallowing was achieved primarily by an increase in the number of bouts of swallowing per day rather than the expected passive increase in volume per bout. This implies changes in fetal behavior as AFV was elevated. Furthermore, swallowed volume was four times more sensitive to increases in AFV than reported previously. Daily swallowed volume in the ovine fetus varies sharply with changes in amniotic fluid volume around normal and reaches a maximum as amniotic fluid volume exceeds 2000 mL. These changes are mediated by altering the number of bouts of swallowing per day rather than the volume swallowed per bout. Retrograde esophageal flow was normally low but became large as daily swallowed volume increased above 900 mL/day.
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Affiliation(s)
- Robert A Brace
- Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Oregon Health and Science University, Portland, Oregon
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Shi L, Mao C, Zeng F, Zhang L, Xu Z. Central angiotensin I increases swallowing activity and oxytocin release in the near-term ovine fetus. Neuroendocrinology 2012; 95:248-56. [PMID: 22086358 PMCID: PMC3701448 DOI: 10.1159/000332736] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 06/28/2011] [Indexed: 11/19/2022]
Abstract
The brain renin-angiotensin system (RAS) plays an important role in hydromineral and neuroendocrine balance. Although previous studies showed that exogenous angiotensin (Ang) II increased dipsogenic and vasopressin responses in near-term fetuses, little is known about the functional development of fetal endogenous brain RAS in the regulation of body fluid homeostasis. To determine the functional development of the central angiotensin-converting enzyme (ACE) in utero, we investigated the electrocortical (ECoG) activity, swallowing activity, oxytocin (OT) release, and c-fos expression in response to intracerebroventricular Ang I administration in the near-term fetal lamb. Ang I did not change fetal low-voltage (LV) and high-voltage (HV) ECoG temporal distributions, but increased fetal swallowing activity during LV ECoG (1.0±0.1 to 3.5±0.4 swallows/min). Additionally, Ang I evoked an increase in c-fos-immunoreactivity in putative dipsogenic centers, including the supraoptic and paraventricular nuclei of the hypothalamus, accompanied by an increase in fetal plasma OT levels. The expression of c-fos was demonstrated in OT neurons in the hypothalamus. The Ang I-mediated increase in fetal swallowing and plasma OT was inhibited by captopril. These results demonstrate the functional development of the fetal brain ACE system in the last trimester of gestation, which plays an important role in the RAS-mediated dipsogenic response and OT release in the regulation of body fluid homeostasis.
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Affiliation(s)
- Lijun Shi
- Beijing Sport University, Beijing, The First Hospital of Soochow University, Suzhou, PR China
| | - Caiping Mao
- Beijing Sport University, Beijing, The First Hospital of Soochow University, Suzhou, PR China
| | - Fanxing Zeng
- Beijing Sport University, Beijing, The First Hospital of Soochow University, Suzhou, PR China
| | - Lubo Zhang
- Beijing Sport University, Beijing, The First Hospital of Soochow University, Suzhou, PR China
- Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, Calif., USA
| | - Zhice Xu
- Beijing Sport University, Beijing, The First Hospital of Soochow University, Suzhou, PR China
- Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, Calif., USA
- *Zhice Xu, Institute for Fetal-Origin Diseases, The First Hospital of Soochow University, 188 Shizhi Rd., Suzhou 215007 (PR China), Tel. +86 512 6185 9998, E-Mail
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Babaei A, Kern M, Antonik S, Mepani R, Ward BD, Li SJ, Hyde J, Shaker R. Enhancing effects of flavored nutritive stimuli on cortical swallowing network activity. Am J Physiol Gastrointest Liver Physiol 2010; 299:G422-9. [PMID: 20508154 PMCID: PMC2928539 DOI: 10.1152/ajpgi.00161.2010] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A better understanding of the central control of the physiology of deglutition is necessary for devising interventions aimed at correcting pathophysiological conditions of swallowing. Positive modulation of the cortical swallowing network can have clinical ramifications in dysphagia due to central nervous system deficits. Our aim was to determine the effect of nutritive sensory input on the cortical swallowing network. In 14 healthy right-handed volunteers, we utilized a paradigm-driven protocol to quantify the number of activated voxels and their signal intensity within the left hemispheric cortical swallowing network by high-resolution functional MRI (fMRI) during five different swallowing conditions. Swallowing conditions included a dry swallow (saliva) and natural water-, lemon-, popcorn-, and chocolate-flavored liquid swallows. Each flavored liquid was presented simultaneously by its image, scent, and taste in random order and tested over three runs. fMRIs were analyzed in a blinded fashion. Average fMRI blood oxygenation level-dependent signal intensity and number of activated voxels during swallowing concurrent with nutritive gustatory, olfactory, and visual stimulations were significantly increased compared with dry/natural water swallows throughout the cortical swallowing network (P < 0.001 and P < 0.05, respectively). Subregion analysis showed the increased activity for flavored liquids in prefrontal, cingulate gyrus, and sensory/motor cortex, but not in precuneus and insula. Concurrent gustatory, olfactory, and visual nutritive stimulation enhances the activity of the cortical swallowing network. This finding may have clinical implications in management of swallowing disorders due to cortical lesions.
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Affiliation(s)
- Arash Babaei
- 1Division of Gastroenterology and Hepatology, and
| | - Mark Kern
- 1Division of Gastroenterology and Hepatology, and
| | | | | | - B. Douglas Ward
- 2Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Shi-Jiang Li
- 2Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - James Hyde
- 2Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Reza Shaker
- 1Division of Gastroenterology and Hepatology, and
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Mao C, Shi L, Xu F, Zhang L, Xu Z. Development of fetal brain renin-angiotensin system and hypertension programmed in fetal origins. Prog Neurobiol 2009; 87:252-63. [PMID: 19428956 DOI: 10.1016/j.pneurobio.2008.12.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2008] [Revised: 10/27/2008] [Accepted: 12/16/2008] [Indexed: 11/30/2022]
Abstract
Since the concept of fetal origins of adult diseases was introduced in 1980s, the development of the renin-angiotensin system (RAS) in normal and abnormal patterns has attracted attention. Recent studies have shown the importance of the fetal RAS in both prenatal and postnatal development. This review focuses on the functional development of the fetal brain RAS, and ontogeny of local brain RAS components in utero. The central RAS plays an important role in the control of fetal cardiovascular responses, body fluid balance, and neuroendocrine regulation. Recent progress has been made in demonstrating that altered fetal RAS development as a consequence of environmental insults may impact on "programming" of hypertension later in life. Given that the central RAS is of equal importance to the peripheral RAS in cardiovascular regulation, studies on the fetal brain RAS development in normal and abnormal patterns could shed light on "programming" mechanisms of adult cardiovascular diseases in fetal origins.
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Affiliation(s)
- Caiping Mao
- Perinatal Biology Center, Soochow University School of Medicine, Suzhou 215007, China
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Ran-Ressler RR, Devapatla S, Lawrence P, Brenna JT. Branched chain fatty acids are constituents of the normal healthy newborn gastrointestinal tract. Pediatr Res 2008; 64:605-9. [PMID: 18614964 PMCID: PMC2662770 DOI: 10.1203/pdr.0b013e318184d2e6] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Vernix suspended in amniotic fluid is normally swallowed by the late term fetus. We hypothesized that branched chain fatty acids (BCFA), long known to be major vernix components, would be found in meconium and that the profiles would differ systematically. Vernix and meconium were collected from term newborns and analyzed. BCFA-containing lipids constituted about 12% of vernix dry weight, and were predominantly saturated, and had 11-26 carbons per BCFA. In contrast, meconium BCFA had 16-26 carbons, and were about 1% of dry weight. Meconium BCFA were mostly in the iso-configuration, whereas vernix BCFA contained dimethyl and middle chain branching, and five anteiso-BCFA. The mass of BCFA entering the fetal gut as swallowed vernix particles is estimated to be 180 mg in the last month of gestation whereas the total mass of BCFA found in meconium is estimated to be 16 mg, thus most BCFA disappear from the fetal gut. The BCFA profiles of vernix and meconium show that BCFA are major components of normal healthy term newborn gastrointestinal tract. BCFA are candidates for agents that play a role in gut colonization and should be considered a nutritional component for the fetus/newborn.
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Affiliation(s)
- Rinat R Ran-Ressler
- Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA
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Shi L, Mao C, Zeng F, Zhu L, Xu Z. Central cholinergic mechanisms mediate swallowing, renal excretion, and c-fos expression in the ovine fetus near term. Am J Physiol Regul Integr Comp Physiol 2008; 296:R318-25. [PMID: 19005017 DOI: 10.1152/ajpregu.90632.2008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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 = 5) or carbachol (3 microg/kg, n = 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+, K+, and Cl(-) 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.
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Affiliation(s)
- Lijun Shi
- Department of Human Sport Science, Beijing Sport University, Beijing, China
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El-Haddad MA, Chao CR, Ma SX, Ross MG. Neuronal NO modulates spontaneous and ANG II-stimulated fetal swallowing behavior in the near-term ovine fetus. Am J Physiol Regul Integr Comp Physiol 2002; 282:R1521-7. [PMID: 11959696 DOI: 10.1152/ajpregu.00229.2001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Spontaneous fetal swallowing occurs at a markedly higher rate compared with spontaneous adult drinking activity. This high rate of fetal swallowing is critical for amniotic fluid volume regulation. Central NO is critical for maintaining the normal rate of fetal swallowing, as nonselective inhibition of NO (with central N(G)-nitro-L-arginine methyl ester) suppresses spontaneous and angiotensin II (ANG II)-stimulated swallowing. We sought to differentiate the contributions of central endothelial vs. neuronal NO in the regulation of spontaneous and stimulated fetal swallowing, using a selective neuronal NO synthase (nNOS) inhibitor. Six time-dated pregnant ewes and fetuses were chronically prepared with fetal vascular and intracerebroventricular (i.c.v.) catheters and electrocorticogram (ECoG) and esophageal electromyogram electrodes and studied at 130 +/- 1 days of gestation. After an initial 2-h baseline period (0-2 h), the selective nNOS inhibitor N-propyl-L-arginine (NPLA) was injected i.c.v. (2-4 h). At 4 h, the dose of NPLA was repeated, together with ANG II, and fetal swallowing was monitored for a final 2 h. Four fetuses also received an identical control study (on an alternate day) in which NPLA was replaced with artificial cerebrospinal fluid (aCSF). Suppression of nNOS by i.c.v. NPLA significantly reduced mean (+/- SE) spontaneous fetal swallowing (1.35 +/- 0.12 to 0.50 +/- 0.07 swallows/min; P < 0.001). Injection of ANG II in the presence of NPLA had no dipsogenic effect on fetal swallowing (0.68 +/- 0.09 swallows/min). In the aCSF study, i.c.v. aCSF did not change fetal swallowing (0.93 +/- 0.10 vs. 0.95 +/- 0.09 swallows/min), whereas i.c.v. ANG II resulted in a significant increase in the rate of fetal swallowing (2.0 +/- 0.04 swallows/min; P = 0.001). We speculate that the suppressive dipsogenic effects of central NPLA indicate that spontaneous and ANG II- stimulated fetal swallowing is dependent on central nNOS activity.
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Affiliation(s)
- Mostafa A El-Haddad
- Perinatal Research Laboratories, Harbor/University of California at Los Angeles Medical Center, University of California at Los Angeles School of Medicine, Torrance, California 90902, USA.
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Xu Z, Glenda C, Day L, Yao J, Ross MG. Central angiotensin induction of fetal brain c-fos expression and swallowing activity. Am J Physiol Regul Integr Comp Physiol 2001; 280:R1837-43. [PMID: 11353690 DOI: 10.1152/ajpregu.2001.280.6.r1837] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study examined physiological and cellular responses to central application of ANG II in ovine fetuses and determined the fetal central ANG-mediated dipsogenic sites in utero. Chronically prepared near-term ovine fetuses (130 +/- 2 days) received injection of ANG II (1.5 microg/kg icv). Fetuses were monitored for 3.5 h for swallowing activity, after which animals were killed and fetal brains were perfused for subsequent Fos staining. Intracerebroventricular ANG II significantly increased fetal swallowing in near-term ovine fetuses (1.1 +/- 0.2 to 4.5 +/- 1.0 swallows/min). The initiation of stimulated fetal swallowing activity was similar to the latency of thirst responses (drinking behavior) elicited by central ANG II in adult animals. ANG II evoked increased Fos staining in putative dipsogenic centers, including the subfornical organ, organum vasculosum of the lamina terminalis, and median preoptic nucleus. Intracerebroventricular injection of ANG II also caused c-fos expression in the fetal hindbrain. These results indicate that an ANG II-mediated central dipsogenic mechanism is intact before birth, acting at sites consistent with the dipsogenic neural network. Central ANG II mechanisms likely contribute to fetal body fluid and amniotic fluid regulation.
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Affiliation(s)
- Z Xu
- Perinatal Research Laboratory, Department of Obstetrics and Gynecology, Harbor/University of California at Los Angeles Medical Center, Research and Education Institute, Torrance, California 90502, USA
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