Development of patterns of respiratory activity in unanesthetized fetal sheep in utero

Bowes, Glenn; Adamson, T. M.; Ritchie, B. C.; Dowling, Margaret H.; Wilkinson, Marcia; Maloney, J. E.

doi:10.1152/jappl.1981.50.4.693

Cited by 50 publications

(20 citation statements)

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“…It is possible that this difference simply reflects the marginally older mean gestational age at which the recordings were made in this group (136 vs. 131 days). It is well established that the incidence of FBMs is lower with increasing gestational age (Bowes, Adamson, Ritchie, Dowling, Wilkinson & Maloney, 1981) and indeed in the present study the incidence of FBMs decreased in the older fetuses in both lighting groups.…”

Section: Fetal Breathing Movementssupporting

confidence: 78%

Effects of different lighting regimes on daily hormonal and behavioural rhythms in the pregnant ewe and sheep fetus.

McMillen

Walker

1991

The Journal of Physiology

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1. We have studied the effect of altering the time of darkness during a 12 h photoperiod on the diurnal rhythms of maternal and fetal plasma melatonin and prolactin concentrations and fetal breathing movements (FBMs) in the late pregnant sheep. 2. Four ewes were exposed to a ‘normal’ 12 h light‐12 h dark regime with lights off at 19.00 h. Eight ewes were exposed to an ‘altered’ 12 h light‐12 h dark regime with lights off at 11.00 h. FBMs were recorded continuously and 2 hourly maternal and fetal blood samples taken during 24 h experiments between 120 and 138 days gestation. 3. Plasma melatonin concentrations were higher during the hours of darkness in the ewes and fetuses in both the normal and altered groups; i.e. altering the time of darkness was associated with a shift in the timing of the daily increase in melatonin concentrations in the mother and fetus. 4. In the fetuses, the mean 24 h plasma prolactin concentration was higher in the altered lighting group (28.8 +/‐ 6.1 micrograms/l) compared to the normal lighting group (13.0 +/‐ 3.9 micrograms/l). There was no difference, however, between groups in the daily variation of fetal plasma prolactin concentrations, which were higher at 17.00‐01.00 h than at 05.00‐19.00 h. Thus, altering the time of darkness did not change the timing of the daily plasma prolactin rhythm in the fetus. 5. Under the normal lighting regime maternal plasma prolactin concentrations were higher at 17.00‐19.00 h (i.e. from 2 h before lights off) than at 09.00‐11.00 h. In contrast, under altered lighting, plasma prolactin concentrations were higher at 01.00‐07.00 h (i.e. 2‐8 h after lights on) than at 09.00 h. 6. In the normal lighting group the incidence (min/h) of FBMs were highest at 16.00‐21.00 h and reached a minimum at 05.00‐06.00 h. In contrast, in the altered lighting group the incidence of FBMs was lowest at 19.00‐20.00 h and reached a maximum at 11.00‐12.00 h. 7. The results suggest that the light‐dark cycle influences the diurnal modulation of FBMs, but not the daily variation of fetal plasma prolactin concentrations. The role of plasma melatonin concentrations, and evidence for a photo‐inducible phase of increased prolactin secretion in the fetus, is discussed.

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Section: Fetal Breathing Movementssupporting

confidence: 78%

Effects of different lighting regimes on daily hormonal and behavioural rhythms in the pregnant ewe and sheep fetus.

McMillen

Walker

1991

The Journal of Physiology

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“…Before this time breathing movements are almost continuous. Thereafter they become increasingly episodic, with longer intervening periods of apnoea (Dawes, Gardner, Johnston & Walker, 1980a;Bowes, Adamson, Ritchie, Dowling, Wilkinson & Maloney, 1981). Near term breathing normally occurs only during episodes oflow-voltage electrocortical activity, characteristic of rapid-eye-movement sleep (Dawes, Fox, Leduc, Liggins & Richards, 1972).…”

Section: Introductionmentioning

confidence: 99%

Breathing in fetal lambs: the effect of brain stem section.

Dawes¹,

Gardner²,

Johnston³

et al. 1983

The Journal of Physiology

167

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SUMMARY1. The effects of section of the brain stem caudally (through the upper pons or mid-collicular) or rostrally (through the caudal hypothalamus or anterior commissuresuprachiasmatic nucleus) were studied in fetal lambs from 118 days gestation, after recovery in utero.2. In lambs sectioned caudally, breathing movements and electrocortical activity were dissociated. After some days recovery breathing tended to become continuous, with an abnormal prolongation of inspiratory time. Isocapnic hypoxia caused an increase in the rate and amplitude of breathing. After carotid denervation hypoxia still caused an increase in the amplitude of breathing. 3. In lambs sectioned rostrally, there was also dissociation between breathing movements and electrocortical activity. Breathing remained episodic, with an incidence similar to that of intact fetal lambs. In two lambs after 10 days of recovery the breathing and electrocortical rhythms returned, from time to time, to their normal phasic relationship. Isocapnic hypoxia caused a diminution or arrest of breathing, as in intact lambs.4. The cardiovascular effects of transaction were examined. Baroreflex sensitivity was normal in those lambs sectioned caudally and enhanced in those sectioned rostrally.5. It is concluded first that as a result of rostral section, independent episodic rhythms of fetal breathing and electrocortical activity can be dissociated. Secondly, moderate isocapnic hypoxia causes arrest of fetal breathing indirectly, requiring the integrity of a suprapontine mechanism. And thirdly, after caudal section of the brain stem, hypoxia causes enhancement of fetal breathing efforts, independently of the carotid chemoreceptors. Possible mechanisms are discussed.

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“…In fetal sheep, an inverse correlation exists between gestational age and the total time occupied by the breathing episodes (Bowes et al 1981). Since these studies were performed after the differentiation of low and high voltage electrocortical activity (gestational age > 130 days) it is unlikely that the decrease in FBMs with increasing gestational age was influenced by the presence of such activity.…”

Section: Vagal Feedback and Fetal Breathing Movements (Fbms)mentioning

confidence: 99%

Physiological Society Symposium – Vagal Control: From Axolotl to Man

Lalani

Remmers

Hasan

2001

Experimental Physiology

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CONTENTS Summary BackgroundVagal feedback and fetal breathing movements (FBMs) Role of vagal innervation during transition from fetal to neonatal period SummaryAlthough vagal afferents are active during intrauterine life, vagal denervation does not lead to gross changes in the occurrence of fetal breathing movements. However, lack of volume feedback has profound and deleterious effects on pulmonary compliance and impairs gas exchange during the early neonatal period. Intrathoracic vagal denervation, which spares vocal cord paralysis and upper airway obstruction in spontaneously breathing unanaesthetised neonatal lambs, leads to reduced pulmonary compliance and persistent hypoxaemia. The underlying mechanisms of these adverse effects include slow breathing frequency, prolonged expiratory times, decreased augmented breaths and the inability to maintain dynamic functional residual capacity leading to progressive atelectasis and regional ventilationperfusion mismatch. Our data suggest that intrathoracic vagal denervation does not lead to pulmonary oedema in newborn lambs which most probably occurred because of upper airway obstruction in previous studies. We provide evidence that the vagal afferent fibre-receptor system provides critical feedback for the maintenance of normal breathing patterns and pulmonary gas exchange during the early neonatal period.

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Development of patterns of respiratory activity in unanesthetized fetal sheep in utero

Cited by 50 publications

References 0 publications

Effects of different lighting regimes on daily hormonal and behavioural rhythms in the pregnant ewe and sheep fetus.

Effects of different lighting regimes on daily hormonal and behavioural rhythms in the pregnant ewe and sheep fetus.

Breathing in fetal lambs: the effect of brain stem section.

Physiological Society Symposium – Vagal Control: From Axolotl to Man

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