Amygdalar involvement in respiratory dysfunction.

The brainstem has long been recognized as the major respiratory control center, but it has become increasingly appreciated that areas upstream of the brainstem modulate respiration and airway defensive behaviors. This review aims to define the role of the amygdala, a key temporal brain region essential for limbic function, in respiration and airway defenses. We summarize literature describing roles for the amygdala in control of respiration, swallow, cough, airway smooth muscle contraction, and mucus secretion.

Evidence for peripheral and central actions of codeine to dysregulate swallowing in the anesthetized cat.

Systemic administration of opioids has been associated with aspiration and swallow dysfunction in humans. We speculated that systemic administration of codeine would induce dysfunctional swallowing and that this effect would have a peripheral component. Experiments were conducted in spontaneously breathing, anesthetized cats.

Computer-aided neurophysiology and imaging with open-source PhysImage.

Improved integration between imaging and electrophysiological data has become increasingly critical for rapid interpretation and intervention as approaches have advanced in recent years. Here, we present PhysImage, a fork of the popular public-domain ImageJ that provides a platform for working with these disparate sources of data, and we illustrate its utility using in vitro preparations from murine embryonic and neonatal tissue. PhysImage expands ImageJ's core features beyond an imaging program by facilitating integration, analyses, and display of 2D waveform data, among other new features.

Transcriptome of neonatal preBötzinger complex neurones in Dbx1 reporter mice.

We sequenced the transcriptome of brainstem interneurons in the specialized respiratory rhythmogenic site dubbed preBötzinger Complex (preBötC) from newborn mice. To distinguish molecular characteristics of the core oscillator we compared preBötC neurons derived from Dbx1-expressing progenitors that are respiratory rhythmogenic to neighbouring non-Dbx1-derived neurons, which support other respiratory and non-respiratory functions. Results in three categories are particularly salient.

Transient Suppression of Dbx1 PreBötzinger Interneurons Disrupts Breathing in Adult Mice.

Interneurons derived from Dbx1-expressing precursors located in the brainstem preBötzinger complex (preBötC) putatively form the core oscillator for inspiratory breathing movements. We tested this Dbx1 core hypothesis by expressing archaerhodopsin in Dbx1-derived interneurons and then transiently hyperpolarizing these neurons while measuring respiratory rhythm in vitro or breathing in vagus-intact adult mice. Transient illumination of the preBötC interrupted inspiratory rhythm in both slice preparations and sedated mice.

Functional Interactions between Mammalian Respiratory Rhythmogenic and Premotor Circuitry.

Unlabelled: Breathing in mammals depends on rhythms that originate from the preBötzinger complex (preBötC) of the ventral medulla and a network of brainstem and spinal premotor neurons. The rhythm-generating core of the preBötC, as well as some premotor circuits, consist of interneurons derived from Dbx1-expressing precursors (Dbx1 neurons), but the structure and function of these networks remain incompletely understood. We previously developed a cell-specific detection and laser ablation system to interrogate respiratory network structure and function in a slice model of breathing that retains the preBötC, the respiratory-related hypoglossal (XII) motor nucleus and XII premotor circuits.

Methyl tetra-O-acetyl-α-D-glucopyranuronate: crystal structure and influence on the crystallisation of the β anomer.

Methyl tetra-O-acetyl-β-D-glucopyranuronate (1) and methyl tetra-O-acetyl-α-D-glucopyranuronate (3) were isolated as crystalline solids and their crystal structures were obtained. That of the β anomer (1) was the same as that reported by Root et al., while anomer (3) was found to crystallise in the orthorhombic space group P212121 with two independent molecules in the asymmetric unit.

Mechanisms Leading to Rhythm Cessation in the Respiratory PreBötzinger Complex Due to Piecewise Cumulative Neuronal Deletions.

The mammalian breathing rhythm putatively originates from Dbx1-derived interneurons in the preBötzinger complex (preBötC) of the ventral medulla. Cumulative deletion of ∼15% of Dbx1 preBötC neurons in an in vitro breathing model stops rhythmic bursts of respiratory-related motor output. Here we assemble in silico models of preBötC networks using random graphs for structure, and ordinary differential equations for dynamics, to examine the mechanisms responsible for the loss of spontaneous respiratory rhythm and motor output measured experimentally in vitro.

Robust network oscillations during mammalian respiratory rhythm generation driven by synaptic dynamics.

How might synaptic dynamics generate synchronous oscillations in neuronal networks? We address this question in the preBötzinger complex (preBötC), a brainstem neural network that paces robust, yet labile, inspiration in mammals. The preBötC is composed of a few hundred neurons that alternate bursting activity with silent periods, but the mechanism underlying this vital rhythm remains elusive. Using a computational approach to model a randomly connected neuronal network that relies on short-term synaptic facilitation (SF) and depression (SD), we show that synaptic fluctuations can initiate population activities through recurrent excitation.

The retrotrapezoid nucleus neurons expressing Atoh1 and Phox2b are essential for the respiratory response to CO₂.

Maintaining constant CO2 and H(+) concentrations in the arterial blood is critical for life. The principal mechanism through which this is achieved in mammals is the respiratory chemoreflex whose circuitry is still elusive. A candidate element of this circuitry is the retrotrapezoid nucleus (RTN), a collection of neurons at the ventral medullary surface that are activated by increased CO2 or low pH and project to the respiratory rhythm generator.

Laser ablation of Dbx1 neurons in the pre-Bötzinger complex stops inspiratory rhythm and impairs output in neonatal mice.

To understand the neural origins of rhythmic behavior one must characterize the central pattern generator circuit and quantify the population size needed to sustain functionality. Breathing-related interneurons of the brainstem pre-Bötzinger complex (preBötC) that putatively comprise the core respiratory rhythm generator in mammals are derived from Dbx1-expressing precursors. Here, we show that selective photonic destruction of Dbx1 preBötC neurons in neonatal mouse slices impairs respiratory rhythm but surprisingly also the magnitude of motor output; respiratory hypoglossal nerve discharge decreased and its frequency steadily diminished until rhythm stopped irreversibly after 85±20 (mean ± SEM) cellular ablations, which corresponds to ∼15% of the estimated population.

Supramolecular stacking motifs in the solid state of amide and triazole derivatives of cellobiose.

1-Acetamido-1-deoxy-(4-O-β-d-glucopyranosyl-β-d-glucopyranose) (5) and 1-deoxy-1-(4-phenyl-1,2,3-triazolyl)-(4-O-β-d-glucopyranosyl-β-d-glucopyranose) (7) were synthesised from 1-azido-1-deoxy-(4-O-β-d-glucopyranosyl-β-d-glucopyranose) (2) and crystallised as dihydrates. Crystal structural analysis of 5·2H2O displayed an acetamide C(4) chain and stacked cellobiose residues. The structure of 7·2H2O featured π-π stacking and stacking of the cellobiose residues.

Hydrogen bonding in crystal forms of primary amide functionalised glucose and cellobiose.

A glucoside and cellobioside of glycolamide were synthesised and the crystal chemistry of these compounds investigated. The amidoglucoside crystallised in the P2(1) space group. The primary amide group participates in C(7) and C(17) chains also involving the pyranose oxygen and hydroxyl groups.

Automated cell-specific laser detection and ablation of neural circuits in neonatal brain tissue.

A key feature of neurodegenerative disease is the pathological loss of neurons that participate in generating behaviour. To investigate network properties of neural circuits and provide a complementary tool to study neurodegeneration in vitro or in situ, we developed an automated cell-specific laser detection and ablation system. The instrument consists of a two-photon and visible-wavelength confocal imaging setup, controlled by executive software, that identifies neurons in preparations based on genetically encoded fluorescent proteins or Ca(2+) imaging, and then sequentially ablates cell targets while monitoring network function concurrently.

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

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.

Preparation and characterisation of solid state forms of paracetamol-O-glucuronide.

The synthesis and crystallisation of the pharmaceutically important metabolite, paracetamol-O-glucuronide, is described. Hydrated and anhydrous forms of the target molecule have been characterised by PXRD, DSC and TGA. In addition, a methanol solvate has been analysed, including single crystal analysis, which represents the first structure solution for this system.

Clonal analysis by distinct viral vectors identifies bona fide neural stem cells in the adult zebrafish telencephalon and characterizes their division properties and fate.

Neurogenesis is widespread in the zebrafish adult brain through the maintenance of active germinal niches. To characterize which progenitor properties correlate with this extensive neurogenic potential, we set up a method that allows progenitor cell transduction and tracing in the adult zebrafish brain using GFP-encoding retro- and lentiviruses. The telencephalic germinal zone of the zebrafish comprises quiescent radial glial progenitors and actively dividing neuroblasts.

Dendritic calcium activity precedes inspiratory bursts in preBotzinger complex neurons.

Medullary interneurons of the preBötzinger complex assemble excitatory networks that produce inspiratory-related neural rhythms, but the importance of somatodendritic conductances in rhythm generation is still incompletely understood. Synaptic input may cause Ca(2+) accumulation postsynaptically to evoke a Ca(2+)-activated inward current that contributes to inspiratory burst generation. We measured Ca(2+) transients by two-photon imaging dendrites while recording neuronal somata electrophysiologically.

Synaptically activated burst-generating conductances may underlie a group-pacemaker mechanism for respiratory rhythm generation in mammals.

Breathing, chewing, and walking are critical life-sustaining behaviors in mammals that consist essentially of simple rhythmic movements. Breathing movements in particular involve the diaphragm, thorax, and airways but emanate from a network in the lower brain stem. This network can be studied in reduced preparations in vitro and using simplified mathematical models that make testable predictions.

Developmental origin of preBötzinger complex respiratory neurons.

A subset of preBötzinger Complex (preBötC) neurokinin 1 receptor (NK1R) and somatostatin peptide (SST)-expressing neurons are necessary for breathing in adult rats, in vivo. Their developmental origins and relationship to other preBötC glutamatergic neurons are unknown. Here we show, in mice, that the "core" of preBötC SST(+)/NK1R(+)/SST 2a receptor(+) (SST2aR) neurons, are derived from Dbx1-expressing progenitors.

Calcium-activated nonspecific cation current and synaptic depression promote network-dependent burst oscillations.

Central pattern generators (CPGs) produce neural-motor rhythms that often depend on specialized cellular or synaptic properties such as pacemaker neurons or alternating phases of synaptic inhibition. Motivated by experimental evidence suggesting that activity in the mammalian respiratory CPG, the preBötzinger complex, does not require either of these components, we present and analyze a mathematical model demonstrating an unconventional mechanism of rhythm generation in which glutamatergic synapses and the short-term depression of excitatory transmission play key rhythmogenic roles. Recurrent synaptic excitation triggers postsynaptic Ca(2+)-activated nonspecific cation current (I(CAN)) to initiate a network-wide burst.

Asymmetric control of inspiratory and expiratory phases by excitability in the respiratory network of neonatal mice in vitro.

Rhythmic motor behaviours consist of alternating movements, e.g. swing-stance in stepping, jaw opening and closing during chewing, and inspiration-expiration in breathing, which must be labile in frequency, and in some cases, in the duration of individual phases, to adjust to physiological demands.

4-Aminopyridine-sensitive outward currents in preBötzinger complex neurons influence respiratory rhythm generation in neonatal mice.

We measured a low-threshold, inactivating K+ current, i.e. A-current (I(A)), in respiratory neurons of the preBötzinger complex (preBötC) in rhythmically active slice preparations from neonatal C57BL/6 mice.

What role do pacemakers play in the generation of respiratory rhythm?

The pacemaker hypothesis that specialized neurons with conditional oscillatory- bursting properties are obligatory for respiratory rhythm generation in vitro has gained widespread acceptance, despite lack of direct proof. Here we critique the pacemaker hypothesis and provide an alternative explanation for rhythmogenesis based on emergent network properties. Pacemaker neurons in the preBötC depend on either persistent Na+ current I(NaP) or Ca(2+)-activated nonspecific cationic current (I(CAN)).