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

Abstract

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.

Neurexins control the strength and precise timing of glycinergic inhibition in the auditory brainstem

“…Consistently, transcriptomic analysis has revealed that the expression profiles of various neurexins differ remarkably in excitatory neurons versus inhibitory neurons even among distinct subtypes of interneurons (Foldy et al, 2016 ;Fuccillo et al, 2015 ;Lukacsovich et al, 2019 ;Uchigashima et al, 2019 ). Despite the multifaceted roles of neurexins widely observed in various glutamatergic and GABAergic synapses (Boxer and Aoto, 2022 ;Chen et al, 2017 ;Luo et al, 2021 ;Sudhof, 2017 ), however, it remains largely unknown how neurexins may regulate the functional properties of the glycinergic synapses, which mediate essential inhibition in the spinal cord, brainstem and retina (Assareh et al, 2023 ;Brill et al, 2020 ;Chang et al, 2023 ;Feng et al, 1998 ;Foster et al, 2015 ;Gomeza et al, 2003a ;Gomeza et al, 2003b ;Zeilhofer et al, 2012 ).…”

Neurexins control the strength and precise timing of glycinergic inhibition in the auditory brainstem

“…Consistently, transcriptomic analysis has revealed that the expression profiles of various neurexins differ remarkably in excitatory neurons versus inhibitory neurons even among distinct subtypes of interneurons ( Földy et al, 2016 ; Fuccillo et al, 2015 ; Lukacsovich et al, 2019 ; Uchigashima et al, 2019 ). Despite the multifaceted roles of neurexins widely observed in various glutamatergic and GABAergic synapses ( Boxer and Aoto, 2022 ; Chen et al, 2017 ; Luo et al, 2021 ; Südhof, 2017 ), however, it remains largely unknown how neurexins may regulate the functional properties of the glycinergic synapses, which mediate essential inhibition in the spinal cord, brainstem and retina ( Assareh et al, 2023 ; Brill et al, 2020 ; Chang et al, 2023 ; Feng et al, 1998 ; Foster et al, 2015 ; Gomeza et al, 2003a ; Gomeza et al, 2003b ; Zeilhofer et al, 2012 ).…”

Neurexins control the strength and precise timing of glycinergic inhibition in the auditory brainstem

“…Consistently, transcriptomic analysis has revealed that the expression profiles of various neurexins differ remarkably in excitatory neurons versus inhibitory neurons even among distinct subtypes of interneurons (Foldy et al, 2016; Fuccillo et al, 2015; Lukacsovich et al, 2019; Uchigashima et al, 2019). Despite the multifaceted roles of neurexins widely observed in various glutamatergic and GABAergic synapses (Boxer and Aoto, 2022; Chen et al ., 2017; Luo et al, 2021; Sudhof, 2017), however, it remains largely unknown how neurexins may regulate the functional properties of the glycinergic synapses, which mediate essential inhibition in the spinal cord, brainstem and retina (Assareh et al, 2023; Brill et al, 2020; Chang et al, 2023; Feng et al, 1998; Foster et al, 2015; Gomeza et al, 2003a; Gomeza et al, 2003b; Zeilhofer et al, 2012).…”