Biology subjects

Oliveira, L. M.

Publications and source records attributed to Oliveira, L. M..

7 recordsLinked to original sources

bioRxiv2025

An inspiration-off attractor supports the robust and flexible control of breathing

Breathing is a fundamental motor rhythm necessary to sustain life. The rhythm and pattern of breathing arises from the coordination of a bilaterally symmetric, rostro-caudally extended column of heterogeneous neural populations in the medulla called the Ventral Respiratory Column (VRC). By recording from the extent of the VRC using Neuropixels during optogenetic and physiological manipulations, and projecting the population activity into a dynamical latent space, we find that GABAergic lung-stretch feedback circuits promote rhythmic population activity by creating a temporary stable fixed point in the latent state that terminates diaphragmatic contraction. Stimulation of GABAergic circuits either intrinsic to the VRC (VRCGABA) or via afferent pathways from GABAergic neurons of the Nucleus of the Solitary Tract (NTSGABA) advance or delay breathing when activated with specific respiratory phase through temporary stabilization of this fixed point. Lastly, we show that activation of glutamatergic signaling opposes the effects of inhibitory signaling by destabilizing this expiratory fixed point to promote rapid inspiration. Together, we decompose the functional impact of different respiratory control subpopulations to reveal an integrated network level mechanism for respiratory control in vivo.

neuroscience↗

bioRxiv2025

Functional Modulation of Retrotrapezoid Neurons Drives Fentanyl-Induced Respiratory Depression

The primary cause of death from opioid overdose is opioid-induced respiratory depression (OIRD), characterized by severe suppression of respiratory rate, destabilized breathing patterns, hypercapnia, and heightened risk of apnea. The retrotrapezoid nucleus (RTN), a critical chemosensitive brainstem region in the rostral ventrolateral medullary reticular formation contains Phox2b+/Neuromedin-B (Nmb) propriobulbar neurons. These neurons, stimulated by CO2/H+, regulate breathing to prevent respiratory acidosis. Since the RTN shows limited expression of opioid-receptors, we expected that opioid-induced hypoventilation should activate these neurons to restore ventilation and stabilize arterial blood gases. However, the ability of the RTN to stimulate ventilation during OIRD has never been tested. We used optogenetic and pharmacogenetic approaches, to activate and inhibit RTN Phox2B+/Nmb+ neurons before and after fentanyl administration. As expected, fentanyl (500 {micro}g/kg, ip) suppressed respiratory rate and destabilized breathing. Before fentanyl, optogenetic stimulation of Phox2b+/Nmb+ or chemogenetic inhibition of Nmb+ cells increased and decreased breathing activity, respectively. Surprisingly, optogenetic stimulation after fentanyl administration caused a significantly greater increase in breathing activity compared to pre-fentanyl levels. By contrast chemogenetic ablation of RTN Nmb neurons caused profound hypoventilation and breathing instability after fentanyl. The results suggest that fentanyl does not inhibit the ability of Phox2b+/Nmb+ cells within the RTN region to stimulate breathing. Thus, this study highlights the potential of stimulating RTN neurons as a therapeutic approach to restore respiratory function in cases of OIRD.

physiology↗

bioRxiv2025

Fentanyl blockade of K+ channels contribute to Wooden Chest Syndrome

Fentanyl is a potent synthetic opioid widely used perioperatively and illicitly as a drug of abuse 1,2. It is well established that fentanyl acts as a -opioid receptor agonist, signaling through Gi/o intracellular pathways to inhibit electrical excitability, resulting in analgesia and respiratory depression 3,4. However, fentanyl uniquely also triggers muscle rigidity, including respiratory muscles, hindering the ability to execute central respiratory commands or to receive external resuscitation. This potentially lethal condition is termed Wooden Chest Syndrome (WCS), the mechanisms of which are poorly understood 5-7. Here we show that fentanyl directly blocks a subset of EAG-class potassium channels 8. Our results also demonstrate that these channels are widely expressed in cervical spinal motoneurons, including those innervating the diaphragm. A significant fraction of these motoneurons is excited by fentanyl, concomitant with blockade of voltage-dependent non-inactivating K+ currents. In vivo electromyography revealed a persistent tonic component of diaphragmatic muscle activity elicited by fentanyl, but not morphine. Taken together our results identify a novel off-target mechanism for fentanyl action, independent of -opioid receptor activation, with a paradoxical excitatory effect that may underlie WCS. We anticipate these findings may inform the design of safer analgesics and generalize to other neuronal circuits implicated in fentanyl-related maladaptive behaviors.

neuroscience↗

bioRxiv2024

Ndufs4 inactivation in glutamatergic neurons reveals swallow-breathing discoordination in a mouse model of Leigh Syndrome

Swallowing, both nutritive and non-nutritive, is highly dysfunctional in children with Leigh Syndrome (LS) and contributes to the need for both gastrostomy and tracheostomy tube placement. Without these interventions aspiration of food, liquid, and mucus occur resulting in repeated bouts of respiratory infection. No study has investigated whether mouse models of LS, a neurometabolic disorder, exhibit dysfunctions in neuromuscular activity of swallow and breathing integration. We used a genetic mouse model of LS in which the NDUFS4 gene is knocked out (KO) specifically in Vglut2 or Gad2 neurons. We found increased variability of the swallow motor pattern, disruption in breathing regeneration post swallow, and water-induced apneas only in Vglut2 KO mice. These physiological changes likely contribute to weight loss and premature death seen in this mouse model. Following chronic hypoxia (CH) exposure, swallow motor pattern, breathing regeneration, weight, and life expectancy were not changed in the Vglut2-Ndufs4-KO CH mice compared to control, indicating a rescue of phenotypes. These findings show that like patients with LS, Ndufs4 mouse models of LS exhibit swallow impairments as well as swallow-breathing dyscoordination alongside the other phenotypic traits described in previous studies. Understanding this aspect of LS will open roads for the development of future more efficacious therapeutic intervention for this illness.

neuroscience↗

bioRxiv2023

Chronic Intermittent Hypoxia reveals role of the Postinspiratory Complex in swallow pattern generation

Obstructive sleep apnea (OSA) is a prevalent sleep-related breathing disorder that results in multiple bouts of intermittent hypoxia. OSA has many neurologic and systemic comorbidities including dysphagia, or disordered swallow, and discoordination with breathing. However, the mechanism in which chronic intermittent hypoxia (CIH) causes dysphagia is unknown. Recently we showed the Postinspiratory complex (PiCo) acts as an interface between the swallow pattern generator (SPG) and the inspiratory rhythm generator, the preBotzinger Complex, to regulate proper swallow-breathing coordination (Huff et al., 2023). PiCo is characterized by interneurons co-expressing transporters for glutamate (Vglut2) and acetylcholine (ChAT). Here we show that optogenetic stimulation of ChATcre:Ai32, Vglut2cre:Ai32, and ChATcre:Vglut2FlpO:ChR2 mice exposed to CIH does not alter swallow-breathing coordination, but unexpectedly disrupts swallow behavior via triggering variable swallow motor patterns. This suggests, glutamatergic-cholinergic neurons in PiCo are not only critical for the regulation of swallow-breathing coordination, but also play an important role in the modulation of swallow motor patterning. Our study also suggests that swallow disruption, as seen in OSA, involves central nervous mechanisms interfering with swallow motor patterning and laryngeal activation. These findings are crucial for understanding the mechanisms underlying dysphagia, both in OSA and other breathing and neurological disorders.

neuroscience↗

bioRxiv2023

Three Accessory Gene Clusters Drive Host-Adaptation in Group B Streptococcus

Streptococcus agalactiae (Group B Streptococcus, GBS) is a major pathogen of humans and animals, posing a threat to human health as well as food security. Here, we investigate the role of genomic mechanisms, including homologous recombination and horizontal gene transfer, in shaping the population structure of GBS and its adaptation to three major host groups (humans, cattle, fishes). We demonstrate that the GBS population comprises host-specialist, host-adapted lineages as well as host generalists, and that these categories differ in their level or recombination. Although the accessory genome at large varies by lineage rather than host, genome wide association studies show that host association is driven by three accessory genome clusters, regardless of lineage or breadth of the host spectrum. These genomic clusters (scpB in human GBS, lactose operon in bovine GBS, Locus 3 in fish GBS) are known (scpB, Lac.2) or shown here (Locus 3) to be functionally relevant and are shared with other streptococcal species occupying the same host niche. These findings demonstrate the importance of considering the role of non-human host species in the evolution of GBS, including high risk clones that may lead to interspecies transmission and affect efficacy of future GBS vaccines.

genomics↗

bioRxiv2023

Postinspiratory complex acts as a gating mechanism regulating swallow-breathing coordination and other laryngeal behaviors

Breathing needs to be tightly coordinated with upper airway behaviors, such as swallowing. Discoordination leads to aspiration pneumonia, the leading cause of death in neurodegenerative diseases. Here we study the role of the postinspiratory complex, (PiCo) in coordinating breathing and swallowing. Using optogenetic approaches in freely breathing-anesthetized ChATcre, Vglut2cre and co-transmission of ChATcre/Vglut2FlpO mice reveals this small brainstem microcircuit acts as a central gating mechanism for airway protective behaviors. Activation of PiCo during inspiration or the beginning of postinspiration triggers swallow behavior, while there is a higher probability for stimulating laryngeal activation when activated further into expiration, suggesting PiCos role in swallow-breathing coordination. PiCo triggers consistent swallow behavior and preserves physiologic swallow motor sequence, while stimulates laryngeal activation variable to stimulation duration. Sufficient bilateral PiCo activation is necessary for gating function since activation of only a few PiCo neurons or unilateral activation leads to blurred behavioral response. Viral tracing experiments reveal projections from the caudal nucleus of the solitary tract (cNTS), the presumed swallow pattern generator (SPG), to PiCo and vice versa. However, PiCo does not directly connect to laryngeal muscles. Investigating PiCos role in swallow and laryngeal coordination will aid in understanding discoordination in breathing and neurological diseases.

neuroscience↗