Electrophysiological and morphological characteristics of GABAergic respiratory neurons in the mouse pre‐Bötzinger complex

Kuwana, Shun-ichi; Tsunekawa, Naoko; Yanagawa, Yuchio; Okada, Yasumasa; Kuribayashi, Junya; Obata, Kunihiko

doi:10.1111/j.1460-9568.2006.04591.x

Cited by 81 publications

(79 citation statements)

References 40 publications

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“…Disinhibition conditions ensured that deleting inhibitory neurons would not affect the XII output. Inspiratory neurons express both excitatory (25,(30)(31)(32) and inhibitory (12,13) transmitters, but it is not possible to differentiate the two phenotypes based on calcium transients in rhythmically active slices. Therefore, approximately one-half of the targets in our experiments are presumably inhibitory and should be discounted from the lesion tally.…”

Section: Discussionmentioning

confidence: 99%

“…Synaptic inhibition is not essential for rhythmogenesis in vitro, but it influences the amplitude of XII output (10,11). Therefore, we added 5 μM strychnine and picrotoxin to the artificial cerebrospinal fluid (ACSF) before the detection phase so that XII output would be insensitive to the effects of laser-ablating inhibitory neurons (12,13) during the ablation phase.…”

Section: Detecting Inspiratory Neurons In the Prebötc And Ventral Resmentioning

confidence: 99%

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Cumulative lesioning of respiratory interneurons disrupts and precludes motor rhythms in vitro

Hayes

Wang²,

Negro³

2012

Proc. Natl. Acad. Sci. U.S.A.

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How brain functions degenerate in the face of progressive cell loss is an important issue that pertains to neurodegenerative diseases and basic properties of neural networks. We developed an automated system that uses two-photon microscopy to detect rhythmic neurons from calcium activity, and then individually laser ablates the targets while monitoring network function in real time. We applied this system to the mammalian respiratory oscillator located in the pre-Bötzinger Complex (preBötC) of the ventral medulla, which spontaneously generates breathing-related motor activity in vitro. Here, we show that cumulatively deleting preBötC neurons progressively decreases respiratory frequency and the amplitude of motor output. On average, the deletion of 120 ± 45 neurons stopped spontaneous respiratory rhythm, and our data suggest ≈82% of the rhythm-generating neurons remain unlesioned. Cumulative ablations in other medullary respiratory regions did not affect frequency but diminished the amplitude of motor output to a lesser degree. These results suggest that the preBötC can sustain insults that destroy no more than ≈18% of its constituent interneurons, which may have implications for the onset of respiratory pathologies in disease states.central pattern generator | calcium imaging | brainstem C entral pattern generator (CPG) networks produce coordinated motor patterns that underlie behaviors such as breathing, locomotion, and chewing (1, 2). A key issue is not just which cell types generate these patterns of activity, but how many? This question pertains to whether and how cumulative cell loss will impair and, possibly preclude, network function.Breathing consists of inspiratory and expiratory phases. The preBötzinger Complex (preBötC) of the medulla putatively contains the inspiratory CPG (3, 4). Over several days in vivo, saporinmediated destruction of preBötC neurons that express neurokinin-1 receptors (NK1Rs) causes sleep-disordered breathing and fatal respiratory pathology (5, 6). Similarly, acute cell-silencing of a subset of the same NK1R-expressing population of preBötC neurons stops spontaneous breathing in awake adult rats (7). These studies helped to determine the cellular composition of the preBötC and confirmed that it was essential for breathing in an otherwise intact animal, but could not measure the resiliency of the preBötC when faced with silencing or deleting its core piecewise.We examined this issue by using slice preparations that capture the preBötC and spontaneously generate fictive breathing-related activity in vitro. We developed a computer-automated system that detects rhythmically active interneurons via two-photon calcium imaging, stores their physical locations in memory, and then laser ablates the targets sequentially, while electrophysiologically monitoring the motor output of the circuit. We applied this system to the preBötC to test the hypothesis that piecewise destruction of the CPG core would cause graded loss of motor activity up to rhythm cessation. We surmised that this effect ...

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Section: Discussionmentioning

confidence: 99%

Section: Detecting Inspiratory Neurons In the Prebötc And Ventral Resmentioning

confidence: 99%

Cumulative lesioning of respiratory interneurons disrupts and precludes motor rhythms in vitro

Hayes

Wang²,

Negro³

2012

Proc. Natl. Acad. Sci. U.S.A.

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“…More recently, glutamic acid decarboxylase-green fluorescence protein (GAD67-GFP) knockin mice have been used to examine inhibition in respiratory related areas. Recordings from GFP-positive neurons in medullary slices that contained the pre-Bötzinger complex showed that they fired concurrently with the integrated rootlet of HN (30). The spatial projections of these interneurons were not reported.…”

Section: Insufficient Gaba a Inhibition Underlies Tonic Activity In Ementioning

confidence: 99%

Correction of respiratory disorders in a mouse model of Rett syndrome

Abdala

Dutschmann

Bissonnette

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

154

159

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Rett syndrome (RTT) is an autism spectrum disorder caused by mutations in the X-linked gene that encodes the transcription factor methyl-CpG-binding protein 2 (MeCP2). A major debilitating phenotype in affected females is frequent apneas, and heterozygous Mecp2-deficient female mice mimic the human respiratory disorder. GABA defects have been demonstrated in the brainstem of Mecp2-deficient mice. Here, using an intact respiratory network, we show that apnea in RTT mice is characterized by excessive excitatory activity in expiratory cranial and spinal nerves. Augmenting GABA markedly improves the respiratory phenotype. In addition, a serotonin 1a receptor agonist that depresses expiratory neuron activity also reduces apnea, corrects the irregular breathing pattern, and prolongs survival in MeCP2 null males. Combining a GABA reuptake blocker with a serotonin 1a agonist in heterozygous females completely corrects their respiratory defects. The results indicate that GABA and serotonin 1a receptor activity are candidates for treatment of the respiratory disorders in Rett syndrome.R ett syndrome (RTT) is an autism spectrum disorder that is caused by mutations in the X-linked gene that encodes methyl-CpG-binding protein 2 (MeCP2) (1). The role of this transcription factor is incompletely understood. Until recently, on the basis of animal studies primarily in embryonic or early neonatal brain, Mecp2 was considered a translational repressor (2, 3). Recently, however, Skene et al. (4) found in neuronal nuclei of mature (6-8 wk) WT littermates of Mecp2 null males that Mecp2 expression is ≈fivefold greater than that at birth. The amount of Mecp2 bound to DNA was proportional to the methylation density of CpG sequences. Importantly, in adult mice, it has been shown that restoring Mecp2 reverses the abnormalities in mobility, gait, hind limb clasping, tremor, breathing, and general condition that they developed during the period that the transcription factor was deficient (5). Thus, Mecp2 deficiency does not cause neuronal degeneration, nor is it necessary for the correct development of neuronal networks. Strategies aimed at pharmacological corrections of symptoms are therefore essential in treating RTT.Respiratory disorders are prominent and one of the most disturbing features of RTT (6, 7). These abnormalities are faithfully mimicked in mouse models of RTT (8). In Mecp2 null male animals studied in situ phrenic (PN) apneas were characterized by prolonged postinspiratory (post-I) activity in the central vagus nerve (9). Post-I activity is linked to the control of laryngeal adductors that control expiratory airflow and protect the lower airways from aspiration during swallowing. Active breath-hold with laryngeal closure is a common feature of RTT (6,7,10).This raises the possibility that the apneas are due to overactive brainstem expiratory neurons in Mecp2 heterozygote mice, perhaps consequent to a lack of synaptic inhibitory control. In this regard, examination of GABA synaptic inhibition in the ventrolateral medulla of Mec...

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“…Également, le CPB de souris n'exprimant pas le gène Jmjd3 est désorganisé, et dépourvu des cellules exprimant la somatostatine et le R-NK1 (Figure 4 C-D) [4]. Enfin, des populations de neurones inhibiteurs GABAergiques et glycinergiques sont aussi pré-sentes dans le CPB [37,38]. Les neurones du CPB sont hétérogènes, expriment un grand nombre de marqueurs, reçoivent de multiples afférences périphériques et centrales, et ne répondent pas de façon stéréotypée.…”

Section: Le Récepteur Nk1unclassified