Comp Biochem Physiol A Mol Integr Physiol
March 2010
In the chick embryo at day 3, gas exchange occurs by diffusion and oxygen consumption (V(O(2))) does not depend on the cardiovascular convection of O(2). Whether or not this is the case in hypoxia is not known and represents the aim of the study. The heart of chicken embryos at 72 h (stage HH18) was filmed through a window of the eggshell by a camera attached to a microscope.
View Article and Find Full Text PDFCan J Physiol Pharmacol
April 2001
This study examined the possible contribution of vagal stretch receptor activity to the increased power of the Hering-Breuer reflex in hyperthermia in rats during the early postnatal period. Experiments were performed on 10 anesthetized (pentobarbital 40 mg/kg, i.p.
View Article and Find Full Text PDFRecordings were obtained from dorsal column nucleus (DCN) neurons in a neonatal rat brain stem-spinal cord preparation to study their basic electrophysiological properties and responses to stimulation of a dorsal root. Whole-cell patch-clamp recordings were made from 21 neurons that responded to dorsal root stimulation with a fast excitatory postsynaptic potential (EPSP). These neurons were located lateral to, but at the level of, the area postrema at depths of 100-268 microm below the dorsal surface of the brain.
View Article and Find Full Text PDFEvidence suggests that gamma-aminobutyric acid (GABA) is involved in control of breathing and in the hypoxia-related ventilatory depression in newborns. However, this evidence is obtained mainly from studies on anesthetized animals. Because anesthesia may interfere with the GABA system, the objectives of our study were to examine effects of GABA on ventilation (V(E)) and ventilatory response to hypoxia and to reveal effects of repeated hypoxia on GABA concentrations in unanesthetized newborns.
View Article and Find Full Text PDFEffects of saphenous nerve stimulation (SNS) on the Hering-Breuer expiratory-promoting reflex evoked by a positive tracheal pressure (PTR; 5 cmH2O) and on the diaphragmatic EMG (EMG(DI)), inspiratory (TI) and expiratory (TE) time, were studied in 16 urethane-anesthetized (1.2-1.6 g/kg, i.
View Article and Find Full Text PDFThe objective of this study was to evaluate effects of baclofen, a gamma-aminobutyric acid type B (GABAB) receptor agonist, injected into the nucleus of the solitary tract, on the Hering-Breuer inspiratory-inhibitory (TI-inhibitory) and deflation reflexes in urethan-anesthetized adult Wistar rats (n = 7). The TI-inhibitory reflex was estimated from changes in peak amplitude of the integrated diaphragmatic electromyogram and inspiratory time (TI) provoked by airway occlusion at end expiration. The deflation reflex was evaluated from changes in TI and expiration (TE) of the first two breaths (TI-1, TE-1 and TI-2, TE-2) immediately after a decrease in tracheal pressure (Ptr).
View Article and Find Full Text PDFCan J Physiol Pharmacol
October 1995
We tested the hypothesis that gamma-aminobutyric acid (GABA) acting on GABA B receptors modulates vagal C fiber mediated reflexes. The effects of a GABA B receptor agonist, (-)-baclofen, injected bilaterally into the nucleus tractus solitarius (NTS), on the cardiorespiratory response to C fiber stimulation with phenyldiguanide (PDG) introduced into the right atrium were evaluated in urethane-anesthetized Wistar rats. We recorded integrated diaphragmatic EMG (Di) and mean arterial blood pressure (ABP).
View Article and Find Full Text PDFCan J Physiol Pharmacol
June 1995
Baclofen, a gamma-aminobutyric acid (GABA) agonist acting on GABAB receptors, has profound effects on respiratory function. We tested a hypothesis that GABAB receptors are involved in modulation of the respiratory reflexes mediated by pulmonary slowly adapting stretch receptors. Urethane-anesthetized (1.
View Article and Find Full Text PDF1. Pulmonary ventilation was found to be similar in high-altitude and low-altitude newborn infants, but the breathing pattern was deeper and slower at high altitude (Mortola, J.P.
View Article and Find Full Text PDFCan J Physiol Pharmacol
October 1994
The rat has become the preferred animal model for study of the central control of the cardiorespiratory system. However, data in the literature suggest that the role of GABAB receptors in control of the respiratory timing may be different in rats from that in other species. Therefore in this study we investigated cardiorespiratory effects of repeated injections of 0.
View Article and Find Full Text PDFTo estimate posthypoxia depressing effects on newborns, ventilatory and metabolic effects of repeated hypoxia were studied in 1- to 3-day-old (group 1) and 2-wk-old (group 2) conscious rabbits. In group 1 (n = 18), ventilation was measured by means of a flow plethysmograph. The barometric method was used in group 2 (n = 21).
View Article and Find Full Text PDFThe barometric method was used to study effects of acute (AC) and chronic cocaine (CC) on breathing and chemosensitivity in awake rats. Effects of AC were evaluated 15 min after daily intraperitoneal injections, and effects of CC were measured at each week of the 4-wk treatment. Sham rats (group 1, n = 10) were injected with NaCl (0.
View Article and Find Full Text PDFThe potency of the Hering-Breuer inspiratory-inhibitory and expiratory-promoting reflexes decreases with maturation in mammals. The Hering-Breuer deflation reflex is present at birth and its power changes little during postnatal development. Already during the second day of life the airway defence reflex resembles that of the adult rabbits.
View Article and Find Full Text PDFIon-selective microelectrodes were used to record levels of extracellular K+ and Ca2+ concentrations ([K+]o and [Ca2+]o, respectively) and the changes evoked by anoxia in the medulla of anesthetized ventilated newborn rabbits, 1-14 days of age. Resting levels of [K+]o showed significant decline with increasing age. The mean initial level of [K+]o was 6.
View Article and Find Full Text PDFEffects of 10% O2 on the response of the phrenic neurogram to vagal (VS) and saphenous stimulation (SS) were studied in anesthetized and artificially ventilated newborn (group 1: 1-3 days old, n = 13; group 2: 8-14 days old, n = 14) and adult (group 3, n = 12) rabbits. In all animals during ventilation with 100% O2 or 10% O2 in N2, VS caused a reduction in the expiratory phase (Te). Te shortening in response to SS was unaffected by hypoxia in group 3, and was abolished in group 2.
View Article and Find Full Text PDFTo define respiratory effects of peripheral acidemia during early development, we injected lactic acid (LA) into the jugular vein of 32 1- to 7-d-old rabbit pups and four adult rabbits. The body weight of newborns varied between 67 +/- 17 g in 1-d-old and 119.8 +/- 33.
View Article and Find Full Text PDFJ Appl Physiol (1985)
June 1990
Eleven rabbits between the 1st and 28th days of life were anesthetized (ketamine 40 mg/kg and acepromazine 3 mg/kg im) thoracotomized, paralyzed, and artificially ventilated with 50% O2 and 10% O2 in N2 or 100% N2. Three-barreled ion-sensitive microelectrodes were used to measure direct-current potentials, potassium (aK+o) and calcium (aCa2+o) activities, and tissue PO2. During control, mean levels of aK+o and aCa2+o were 4.
View Article and Find Full Text PDFThe aim of this study was to determine whether pulmonary receptors other than slowly adapting stretch receptors are capable of entraining the respiratory rhythm when periodically stimulated during artificial ventilation. Experiments were performed on anaesthetised (urethane, 1.5 g/kg) and paralysed (pancuronium bromide, 0.
View Article and Find Full Text PDFJ Appl Physiol (1985)
February 1988
We studied the respiratory effects of cigarette smoke, 5% histamine aerosol, and dust in unanesthetized 1- to 7-day-old rabbits in a body plethysmograph. Cigarette smoke immediately provoked the animal's arousal and irregular breathing. Histamine and dust had no effect in some of the youngest animals.
View Article and Find Full Text PDFEur J Appl Physiol Occup Physiol
January 1989
The direct impact of changes in end-tidal transpulmonary pressure (P'L) on phrenic (Phr) activity has been investigated in 6 cats anaesthetized with pentobarbital or ketamine. Rapid changes in P'L were accomplished by step-like changes in tracheal pressure (Ptr), i.e.
View Article and Find Full Text PDFExpiratory effects of electrical stimulation of vagal afferents were studied in 12 kittens during the first week of life. Animals anesthetized with ketamine (30 mg/kg, im) and acepromazine (1.1 mg/kg, im), tracheostomized, and paralyzed were artificially ventilated after bilateral vagotomy.
View Article and Find Full Text PDFJ Appl Physiol (1985)
July 1985
Respiratory effects of positive and negative pressure breathing were studied in 1- and 4-day-old rabbit pups anesthetized with ketamine (50 mg/kg, im) and acepromazine (3 mg/kg, im). We recorded tidal volume (VT), tracheal pressure (Ptr), and integrated diaphragmatic EMG (DiEMG). Inspiratory (TI) and expiratory time (TE) were measured from the records of DiEMG.
View Article and Find Full Text PDFJ Appl Physiol (1985)
April 1985
We examined the influence of vagal pulmonary receptors exerted on the breathing pattern and inspiratory activities of phrenic nerve and intercostal electromyograms (EMG) during hypoxia in rabbit pups. Animals in their second week of life were anaesthetized with ketamine (50 mg/kg) and acepromazine (3 mg/kg) and tracheostomized. While they breathed spontaneously, we recorded tidal volume (VT), integrated phrenic activity (PHR), integrated external intercostal EMG (INT), and blood pressure (BP).
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