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Del Negro, C. A.

Publications and source records attributed to Del Negro, C. A..

6 recordsLinked to original sources
bioRxiv2022

Minimal models of the inspiratory and sigh breathing rhythms of the preBötzinger complex

The preBotzinger complex of the lower brainstem generates two breathing-related rhythms: one for inspiration on a timescale of seconds, and another that produces larger amplitude sighs on the order of minutes. We hypothesize that these two disparate rhythms emerge in tandem wherein recurrent excitation gives rise to the inspiratory rhythm while a calcium oscillator generates sighs; distinct neuronal populations are not required. We present several mathematical models that instantiate our working hypothesis including: (1) an activity (firing rate) model and (2) a minimal spiking network model. Both modeling frameworks corroborate the single-population rhythmogenic hypothesis.

neuroscience↗
bioRxiv2022

Sigh breathing rhythm depends on intracellular calcium oscillations in a population of inspiratory rhythmogenic preBötzinger complex neurons in mice

The preBotzinger Complex (preBotC) of the lower brainstem generates two breathing-related rhythms: one for inspiration on a timescale of seconds and another that produces larger amplitude sighs on the order of minutes. Their underlying mechanisms and cellular origins remain incompletely understood. We resolve these problems via a joint experiment and modeling approach. Blocking purinergic gliotransmission does not perturb either rhythm and imaging experiments show that both rhythms emanate from the same glutamatergic neuron population. We hypothesized that these two disparate rhythms emerge in tandem wherein recurrent excitation gives rise to inspiratory rhythm while a calcium oscillator generates sighs; there is no obligatory role for gliotransmission, hyperpolarization activated mixed cationic current (Ih) in neurons, or synaptic inhibition-mediated coupling of separate populations. We developed a mathematical model that instantiates our working hypothesis. Tests of model predictions validate the single-population rhythmogenic framework, reproducing disparate breathing-related frequencies and the ability for inspiratory and sigh rhythms to be separately regulated in support of respiration under a wide array of conditions. Here we show how a single neuron population exploits two cellular tool-kits: one involving voltage-dependent membrane properties and synaptic excitation for inspiratory breathing (eupnea) and an intracellular biochemical oscillator for sighs, which ventilate and maintain optimal function in the compliant mammalian lung. SIGNIFICANCE STATEMENTBreathing consists of two vital rhythms: one for eupnea that serves periodic physiological gas exchange and the other for sighs, which are larger breaths that occur minutes apart and serve to optimize pulmonary function. These rhythms with disparate frequencies emerge via a mechanism that is simpler than previously envisaged: it results from one neuron population (not two as previously thought) without need for gliotransmission or synaptic inhibition-mediated coupling of neuronal populations. We show that a low-frequency intracellular calcium oscillation underlies sighs and functions in parallel with the higher-frequency voltage-dependent network oscillation that drives eupnea. Exploiting two separate cellular tool kits enables quasi-independent breathing rhythms, which are unique features of breathing in mammals with compliant lungs.

neuroscience↗
bioRxiv2021

Transcriptomes of Electrophysiologically Recorded Dbx1-derived Inspiratory Neurons of the preBötzinger Complex in Neonatal Mice

Breathing depends on interneurons in the preBotzinger complex (preBotC) derived from Dbx1-expressing precursors. Here we investigate whether rhythm- and pattern-generating functions reside in discrete classes of Dbx1 preBotC neurons. In a slice model of breathing with [~]5 s cycle period, putatively rhythmogenic Type-1 Dbx1 preBotC neurons activate 100-300 ms prior to Type-2 neurons, putatively specialized for output pattern, and 300-500 ms prior to the inspiratory motor output. We sequenced Type-1 and Type-2 transcriptomes and identified differential expression of 123 genes including ionotropic receptors (Gria3 and Gabra1) that may explain their preinspiratory activation profiles and Ca2+ signaling (Cracr2a, Sgk1) involved in inspiratory and sigh bursts. Surprisingly, neuropeptide receptors that influence breathing (e.g., {micro}-opioid and bombesin-like peptide receptors) were only sparsely expressed, which suggests that cognate peptides and opioid drugs exert their profound effects on a small fraction of the preBotC core. These data in the public domain help explain breathings neural origins.

neuroscience↗
bioRxiv2019

Role of synaptic inhibition in the coupling of the respiratory rhythms that underlie eupnea and sigh behaviors

The preBotzinger Complex (preBotC) gives rise to two types of breathing behavior: eupnea and sighing. Here, we examine the neural mechanisms that couple their underlying rhythms by recording from the preBotC in neonatal mouse brainstem slice preparations. It has been proposed that chloride-mediated synaptic inhibition couples inspiratory (eupnea-related) bursts and sigh bursts, but we find no evidence to support that notion. First, we characterize a fluctuating temporal relationship between sigh bursts and their preceding inspiratory bursts; their coupling is far weaker than previously described. Surprisingly, selective blockade of inhibitory synapses strengthened (rather than weakened) that phasic inspiratory-sigh burst relationship. Furthermore, pharmacological disinhibition did not alter the duration of the prolonged interval that follows a sigh burst prior to resumption of the inspiratory rhythm. These results demonstrate that coupling between inspiratory and sigh rhythms does not depend on synaptic inhibition.\n\nSIGNIFICANCE STATEMENTBreathing consists of eupnea and sigh breaths, which differ in their magnitude and frequency. Both breath types emerge from a brainstem microcircuit that coordinates their timing. Here, we advance understanding of these rhythms by assessing the nature and strength of their coordination, and by showing that synaptic inhibition does not enforce their temporal coupling in contrast to conventional understanding. This study provides insights into the basic neural mechanisms that link oscillations of different amplitude and frequency in a core oscillator.

neuroscience↗
bioRxiv2019

Evaluating the burstlet theory of inspiratory rhythm and pattern generation

The preBotzinger complex (preBotC) generates the rhythm and rudimentary motor pattern for inspiratory breathing movements. Here, we test burstlet theory (Kam, Worrell, Janczewski, et al. 2013), which posits that low amplitude burstlets, subthreshold from the standpoint of inspiratory bursts, reflect the fundamental oscillator of the preBotC. In turn, a discrete suprathreshold process transforms burstlets into full amplitude inspiratory bursts that drive motor output, measurable via hypoglossal nerve (XII) discharge in vitro. We recap observations by Kam & Feldman: field recordings from preBotC demonstrate bursts and concurrent XII motor output intermingled with lower amplitude burstlets that do not produce XII motor output. Manipulations of excitability affect the relative prevalence of bursts and burstlets and modulate their frequency. Whole-cell and photonic recordings of preBotC neurons suggest that burstlets involve inconstant subsets of rhythmogenic interneurons. We conclude that discrete rhythm- and pattern-generating mechanisms coexist in the preBotC and that burstlets reflect its fundamental rhythmogenic nature.

neuroscience↗
bioRxiv2018

Dbx1 pre-Bötzinger complex interneurons comprise the core inspiratory oscillator for breathing in adult mice

The brainstem pre-Botzinger complex (preBotC) generates inspiratory breathing rhythms, but which neurons comprise its rhythmogenic core? Dbx1-derived neurons may play the preeminent role in rhythm generation, an idea well founded at perinatal stages of development but not in adulthood. We expressed archaerhodopsin or channelrhodopsin in Dbx1 preBotC neurons in intact adult mice to interrogate their function. Prolonged photoinhibition slowed down or stopped breathing, whereas prolonged photostimulation sped up breathing. Brief inspiratory-phase photoinhibition evoked the next breath earlier than expected, whereas brief expiratory-phase photoinhibition delayed the subsequent breath. Conversely, brief inspiratory-phase photostimulation increased inspiratory duration and delayed the subsequent breath, whereas brief expiratory-phase photostimulation evoked the next breath earlier than expected. Because they govern the frequency and precise timing of breaths in awake adult mice with sensorimotor feedback intact, Dbx1 preBotC neurons constitute an essential core component of the inspiratory oscillator, knowledge directly relevant to human health and physiology.

neuroscience↗