Increase of breathing rate mediated by unilateral optogenetic inactivation of inhibitory neurons in the preBötzinger Complex in vivo

Vafadari, Behnam; Tacke, Charlotte; Harb, Ali; Grützner, Anja-Annett; Hülsmann, Swen

doi:10.1016/j.resp.2023.104032

Cited by 3 publications

(3 citation statements)

References 21 publications

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“…cat (Schwarzacher et al, 1995) or rat (Hayashi et al, 1996). One reason might be that we had still relatively high respiratory rates 12 with the inspiration being as short as 200 ms (Hulsmann et al, 2021;Vafadari et al, 2023), as compared to 2 s in the cat (Schwarzacher et al, 1995). Indeed, there might be no need for post-inspiratory neurons to fire during the full course of the expiration to induce the phase shift from inspiration to expiration.…”

Section: Discussionmentioning

confidence: 99%

In-vivo optogenetic identification and electrophysiology of glycinergic neurons in pre-Bötzinger complex of mice

Vafadari,

Oku,

Tacke

et al. 2024

Respiratory Physiology & Neurobiology

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Section: Discussionmentioning

confidence: 99%

In-vivo optogenetic identification and electrophysiology of glycinergic neurons in pre-Bötzinger complex of mice

Vafadari,

Oku,

Tacke

et al. 2024

Respiratory Physiology & Neurobiology

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“…We aimed to determine whether preBötC GAD1 + and GAD1 - inhibitory populations play functionally distinct roles in inspiratory rhythm and pattern generation in vitro . Pharmacological blockade of inhibitory transmission, local microinjection, and opsin expression induced in whole animal transgenic mice or by viral infection often affect nearby BötC neurons, and, in the case of whole animal opsin expression, inhibitory inputs from afferents throughout the brainstem (Ausborn et al, 2018; Baertsch et al, 2018; Fortuna et al, 2019; Huff et al, 2022; Hulsmann et al, 2021; Sherman et al, 2015; Vafadari et al, 2023). To overcome this technical obstacle, we used holographic photostimulation to restrict activation to a small number of neurons and to establish that the targeted inhibitory neurons were in preBötC by showing that activating adjacent Dbx1 + neurons entrained inspiratory rhythm.…”

Section: Discussionmentioning

confidence: 99%

“…Optogenetic stimulation of medullary GlyT2 + neurons in vivo delays inspiration, modulates tidal volume, and causes apneas (Ausborn et al, 2018; Fortuna et al, 2019; Hulsmann et al, 2021; Sherman et al, 2015), but has also been shown to increase inspiratory frequency by reducing excitability during inspiration, shortening postinspiratory refractoriness, and evoking post-inhibitory rebound (Baertsch et al, 2018). Optogenetic photoinhibition of GlyT2 + neurons increases tidal volume and shortens expiratory duration (Sherman et al, 2015; Vafadari et al, 2023). preBötC GAD1 + neurons project ipsilaterally to downstream XII premotoneurons and motoneurons at the same coronal level in the medullary slice (Koizumi et al, 2013), indicative of a role in modulating inspiratory burst pattern as activity is transmitted from the preBötC to XII nerve.…”

Section: Introductionmentioning

confidence: 99%

Inhibitory subpopulations in preBötzinger Complex play distinct roles in modulating inspiratory rhythm and pattern

Chang

Skach

Kam

2023

Preprint

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Inhibitory neurons embedded within mammalian neural circuits shape breathing, walking, chewing, and other rhythmic motor behaviors. At the core of the neural circuit controlling breathing is the preBötzinger Complex (preBötC), a nucleus in the ventrolateral medulla necessary for generation of inspiratory rhythm. In the preBötC, a recurrently connected network of glutamatergic Dbx1-derived (Dbx1+) neurons generates rhythmic inspiratory drive to inspiratory premotoneurons and motoneurons. Functionally and anatomically intercalated among Dbx1+preBötC neurons are GABAergic (GAD1/2+) and glycinergic (GlyT2+) neurons, whose functions have not been clearly determined. We first characterized the spatial distribution of molecularly-defined inhibitory preBötC subpopulations in double reporter mice expressing either the red fluorescent protein tdTomato or EGFP in GlyT2+, GAD1+, or GAD2+neurons. We found that, in postnatal mice, the majority of inhibitory preBötC neurons expressed a combination of GlyT2 and GAD2 while a much smaller subpopulation also expressed GAD1. To determine the functional role of these subpopulations, we used holographic photostimulation, a patterned illumination technique with high spatiotemporal resolution, to specifically excite small groups of GlyT2+or GAD1+preBötC subpopulations in rhythmically active medullary slices from Dbx1tdTomato;GlyT2EGFPand Dbx1tdTomato;GAD1EGFPdouble reporter mice. Stimulation of 4 or 8 GlyT2+preBötC neurons during endogenous rhythmic activity prolonged the interburst interval in a phase-dependent manner and increased the latency to burst initiation when bursts were evoked by stimulation of Dbx1+neurons. In contrast, stimulation of 4 or 8 GAD1+preBötC neurons did not affect interburst interval or latency to burst initiation, but did prolong both endogenous and evoked burst duration when stimulation occurred during the burst. We conclude that the majority of inhibitory preBötC neurons express both GlyT2 and GAD2 and affect breathing rhythm by delaying burst initiation while a smaller GAD1+subpopulation affects inspiratory patterning by prolonging burst duration.

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Inhibitory Subpopulations in preBtzinger Complex Play Distinct Roles in Modulating Inspiratory Rhythm and Pattern

Chang,

Skach,

Kam

2024

J. Neurosci.

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Inhibitory neurons embedded within mammalian neural circuits shape breathing, walking, and other rhythmic motor behaviors. At the core of the neural circuit controlling breathing is the preBötzinger Complex (preBötC), where GABAergic (GAD1/2+) and glycinergic (GlyT2+) neurons are functionally and anatomically intercalated among glutamatergic Dbx1-derived (Dbx1+) neurons that generate rhythmic inspiratory drive. The roles of these preBötC inhibitory neurons in breathing remain unclear. We first characterized the spatial distribution of molecularly-defined preBötC inhibitory subpopulations in male and female neonatal double reporter mice expressing either tdTomato or EGFP in GlyT2+, GAD1+, or GAD2+neurons. We found that the majority of preBötC inhibitory neurons expressed both GlyT2 and GAD2 while a much smaller subpopulation also expressed GAD1. To determine the functional role of these subpopulations, we used holographic photostimulation, a patterned illumination technique, in rhythmically active medullary slices from neonatal Dbx1tdTomato;GlyT2EGFPand Dbx1tdTomato;GAD1EGFPdouble reporter mice of either sex. Stimulation of 4 or 8 preBötC GlyT2+neurons during endogenous rhythm prolonged the interburst interval in a phase-dependent manner and increased the latency to burst initiation when bursts were evoked by stimulation of Dbx1+neurons. In contrast, stimulation of 4 or 8 preBötC GAD1+neurons did not affect interburst interval or latency to burst initiation. Instead, photoactivation of GAD1+neurons during the inspiratory burst prolonged endogenous and evoked burst duration and decreased evoked burst amplitude. We conclude that GlyT2+/GAD2+neurons modulate breathing rhythm by delaying burst initiation while a smaller GAD1+subpopulation shapes inspiratory patterning by altering burst duration and amplitude.Significance StatementInhibition is critical for control of rhythmic motor behaviors, such as breathing, walking, and chewing. We reveal functional differences among embedded preBötC inhibitory microcircuits that contribute to excitation-inhibition balance governing distinct processes in the breathing motor program. We develop approaches for high throughput analysis of spatial distributions of neurons in tissue and for dynamic functional manipulations via an important extension of holographic photostimulation to sequences of patterns that more closely mimics physiological neural activity. Our study challenges the current understanding of the role of inhibition in breathing and provides novel insights into specific roles of inhibitory neurons in neural circuits controlling breathing that are applicable to other rhythmic motor behaviors in health and disease.

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Increase of breathing rate mediated by unilateral optogenetic inactivation of inhibitory neurons in the preBötzinger Complex in vivo

Cited by 3 publications

References 21 publications

In-vivo optogenetic identification and electrophysiology of glycinergic neurons in pre-Bötzinger complex of mice

In-vivo optogenetic identification and electrophysiology of glycinergic neurons in pre-Bötzinger complex of mice

Inhibitory subpopulations in preBötzinger Complex play distinct roles in modulating inspiratory rhythm and pattern

Inhibitory Subpopulations in preBtzinger Complex Play Distinct Roles in Modulating Inspiratory Rhythm and Pattern

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