Respiratory rhythm generation in a precocial rodent in vitro preparation

Greer, John J.; Carter, Jo Ellen; Allan, Douglas W.

doi:10.1016/0034-5687(95)00073-9

Cited by 14 publications

(1 citation statement)

References 13 publications

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“…This slow rhythm could represent an alteration of underlying mechanisms of breathing. Brainstem–spinal cords isolated from neonatal spiny mice, which are born in a more mature state of CNS development than rats, do not generate a sustained respiratory activity (Greer, Carter & Allan, 1996).…”

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confidence: 99%

Chemosensory and cholinergic stimulation of fictive respiration in isolated cns of neonatal opossum

Eugenı́n

Nicholls²

1997

The Journal of Physiology

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The aim of the present experiments was to characterize the central chemical drive of fictive respiration in the isolated CNS of the newborn opossum, Monodelphis domestica. This opossum preparation, in contrast to those of neonatal rats and mice, produces respiratory rhythm of high frequency in vitro. Fictive respiration was recorded from C3–C5 ventral roots of the isolated CNS of 4‐ to 14‐day‐old opossums using suction electrodes. At room temperature (21–23 °C) the frequency of respiration was 43 ± 5.3 min−1 (mean ±s.e.m., n= 50) in basal medium Eagle's medium (BMEM) equilibrated with 5% CO2–95% O2, pH 7.37‐7.40. Respiratory discharges remained regular throughout 8 h experiments and continued for more than 20 h in culture. Superfusion of the brainstem confirmed that solutions of pH 6.3–7.2 increased both the amplitude and frequency of respiration. High pH solutions (7.5–7.7) had the opposite effect and abolished the rhythm at pH7.7. Addition of ACh (50–100 μm) or carbachol (0.01–10 μm) to the brainstem superfusion also increased the amplitude and frequency of respiratory activity, as did physostigmine (50–100 μm) or neostigmine (20–50 μm). Conversely, scopolamine (50–100 μm) reduced the amplitude and frequency of the basal respiratory rhythm by about 30%. H+ ‐ and cholinergic‐sensitive areas on the surface of the isolated CNS were explored with a small micropipette (outer tip diameter, 100 μm) filled with BMEM (pH 6.5) or 1 μm carbachol. Carabachol applied to H+ ‐ and cholinergic‐sensitive areas in the ventral medulla mimicked the changes of respiratory pattern produced by low pH application. Responses to altered pH and carbachol were abolished by scopolamine (50 μm). Histochemistry demonstrated several medullary groups of neurons stained for acetylcholinesterase. The superficial location of one of these groups coincided with a functional and anatomically well‐defined pH‐ and carbachol‐sensitive area placed medial to the hypoglossal roots. Exploration of chemosensitive areas revealed that application of drugs or solutions of different pH to a single well‐defined spot could have selective and distinctive effects upon amplitude and frequency of respiratory activity. These results show that fictive respiration in the isolated CNS of the newborn opossum is tonically driven by chemical‐ and cholinergic‐sensitive areas located on the ventral medulla, the activity of which regulates frequency and amplitude of respiration. They suggest that a cholinergic relay, although not essential for rhythm generation, is involved in the central pH chemosensory mechanism, or that cholinergic and chemical inputs converge upon the same input pathway to the respiratory pattern generator.

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Chemosensory and cholinergic stimulation of fictive respiration in isolated cns of neonatal opossum

Eugenı́n

Nicholls²

1997

The Journal of Physiology

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Control of Breathing Activity in the Fetus and Newborn

Greer

2015

Comprehensive Physiology

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Breathing movements have been demonstrated in the fetuses of every mammalian species investigated and are a critical component of normal fetal development. The classic sheep preparations instrumented for chronic fetal monitoring determined that fetal breathing movements (FBMs) occur in aggregates interspersed with long periods of quiescence that are strongly associated with neurophysiological state. The fetal sheep model also provided data regarding the neurochemical modulation of behavioral state and FBMs under a variety of in utero conditions. Subsequently, in vitro rodent models have been developed to advance our understanding of cellular, synaptic, network, and more detailed neuropharmacological aspects of perinatal respiratory neural control. This includes the ontogeny of the inspiratory rhythm generating center, the preBötzinger complex (preBötC), and the anatomical and functional development of phrenic motoneurons (PMNs) and diaphragm during the perinatal period. A variety of newborn animal models and studies of human infants have provided insights into age-dependent changes in state-dependent respiratory control, responses to hypoxia/hypercapnia and respiratory pathologies.

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Fetal Sleep and Spontaneous Behavior In Utero: Animal and Clinical Studies

Rurak

2016

Neuromethods

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Respiratory rhythm generation in a precocial rodent in vitro preparation

Cited by 14 publications

References 13 publications

Chemosensory and cholinergic stimulation of fictive respiration in isolated cns of neonatal opossum

Chemosensory and cholinergic stimulation of fictive respiration in isolated cns of neonatal opossum

Control of Breathing Activity in the Fetus and Newborn

Fetal Sleep and Spontaneous Behavior In Utero: Animal and Clinical Studies

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