The Combined Effects of Sevoflurane and Remifentanil on Central Respiratory Activity and Nociceptive Cardiovascular Responses in Anesthetized Rabbits

Exposure to hyperbaric pressure causes a constellation of motor disturbances and ventilatory difficulties in animals and humans. The present experiments were designed to examine the effects of hyperbaric pressure on the rhythmic activity of the respiratory center in the absence of peripheral sensory afferents by using the isolated brain stem-spinal cord preparation from newborn rats. In addition, we examined the effect of pressure on the response of the respiratory center to sensory input from the trigeminal and vagus cranial nerves. Hyperbaric pressure significantly depressed the mean inspiratory drive (frequency X time integral of single electrical bursts) in C5 but not in C1 ventral roots. Pressure also reduced the amount of inhibition on the respiratory activity normally exerted by trigeminal and vagal nerve stimulation and in some cases reversed it to excitation. It is concluded that in the absence of sensory input, exposure to hyperbaric pressure depresses central respiratory activity. However, in an intact system, it may alter the balance between excitation and inhibition and render the system hyperexcitable to the same sensory input.

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Regulation of fetal breathing

Reproduction Fertility and Development ◽

10.1071/rd9960023 ◽

1996 ◽

Vol 8 (1) ◽

pp. 23 ◽

Cited By ~ 7

Author(s):

H Rigatto

Keyword(s):

Molecular Mass ◽

Umbilical Cord ◽

Neuronal Network ◽

Respiratory Activity ◽

In Utero ◽

Cold Stimulation ◽

The Past ◽

Fetal Breathing ◽

Central Respiratory Activity ◽

Made In

Traditionally, the idea of transient asphyxia plus some degree of cold stimulation has been used to explain the establishment of continuous breathing at birth. This idea was nurtured by observations made in the acute fetal preparation at a time when fetal breathing was considered absent. Experimental observations made in the past two decades have challenged this traditional view. First, complete peripheral chemodenervation, essential to the hypoxic stimulus theory, did not affect fetal breathing or the establishment of continuous breathing at birth. Second, occlusion of the umbilical cord in utero, as long as some oxygenation is provided to the fetus in order to avoid fetal hypoxaemia, establishes continuous breathing in utero, in the absence of all sensorial input thought to be important for the establishment of continuous breathing. These observations led us to hypothesize the presence of a placental factor responsible for the inhibition of breathing in utero. This placental factor appears to be a peptide with a molecular mass between 3.5 and 10 kDa. This review will also explore some new observations regarding the generation of central respiratory activity in the fetus, and suggests that the rhythm generator is a neuronal network in which the unit is a pacemaker-like cell uniquely responsive to CO2.

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Substance P and central respiratory activity: a comparative in vitro study on foetal and newborn rat

Developmental Brain Research ◽

10.1016/s0165-3806(99)00044-9 ◽

1999 ◽

Vol 114 (2) ◽

pp. 217-227 ◽

Cited By ~ 27

Author(s):

Krzysztof Ptak ◽

Eric Di Pasquale ◽

Roger Monteau

Keyword(s):

Substance P ◽

Respiratory Activity ◽

In Vitro Study ◽

Vitro Study ◽

Newborn Rat ◽

Central Respiratory Activity

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Coordination of wingbeat and respiration in birds. II. "Fictive" flight

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.3.1025 ◽

1992 ◽

Vol 73 (3) ◽

pp. 1025-1033 ◽

Cited By ~ 23

Author(s):

G. D. Funk ◽

J. D. Steeves ◽

W. K. Milsom

Keyword(s):

Respiratory Activity ◽

Cardiovascular Responses ◽

Canada Geese ◽

Free Flight ◽

Wingbeat Frequency ◽

Pekin Ducks ◽

Before And After ◽

The Relationship ◽

Respiratory Rhythms ◽

Central Level

To determine whether an interaction between central respiratory and locomotor networks may be involved in the observed coordination of wingbeat and respiratory rhythms during free flight in birds, we examined the relationship between wingbeat and respiratory activity in decerebrate Canada geese and Pekin ducks before and after paralysis. Locomotor activity was induced through electrical stimulation of brain stem locomotor regions. Respiratory frequency (fv) was monitored via pneumotachography and intercostal electromyogram recordings before paralysis and via intercostal and cranial nerve IX electroneurogram recordings after paralysis. Wingbeat frequency (fW) was monitored using pectoralis major electromyogram recordings before, and electroneurogram recordings after, paralysis. Respiratory and cardiovascular responses of decerebrate birds during active (nonparalyzed) and “fictive” (paralyzed) wing activity were qualitatively similar to those of a variety of vertebrate species to exercise. As seen during free flight, wingbeat and respiratory rhythms were always coordinated during electrically induced wing activity. Before paralysis during active wing flapping, coupling ratios (fW/fv) of 1:1, 2:1, 3:1, and 4:1 (wingbeats per breath) were observed. After paralysis, fW and fv remained coupled; however, 1:1 coordination predominated. All animals tested (n = 9) showed 1:1 coordination. Two animals also showed brief periods of 2:1 coupling. It is clear that locomotor and respiratory networks interact on a central level to produce a synchronized output. The observation that the coordination between fW and fv differs in paralyzed and nonparalyzed birds suggests that peripheral feedback is involved in the modulation of a centrally derived coordination.

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