Riley-DiPaolo, A. | Search bioRxiv

bioRxiv2026

Glutamate co-release from catecholaminergic neurons shapes breathing and is inhibited during opioid-induced respiratory depression

Breathing is controlled by a distributed brainstem network that includes multiple catecholaminergic nuclei. The locus coeruleus (LC), the brains primary source of noradrenaline (NA), projects to several respiratory centers, including the Kolliker-Fuse (KF) nucleus in the pons. While LC neurons are predominantly noradrenergic (NAergic), many co-release glutamate, which may contribute to the state-dependent modulation of breathing, particularly during opioid exposure. Here, we examined how opioids affect NAergic and glutamatergic signaling in the LC-KF circuit using optogenetics and whole-cell patch clamp recordings in mouse brain slices. Optogenetic activation of LC terminals evoked glutamatergic excitatory postsynaptic currents (EPSCs) in KF neurons that were presynaptically inhibited by the opioid receptor agonist Met-enkephalin. Additionally, [~]36% of glutamate-responsive KF neurons exhibited postsynaptic opioid inhibition via GIRK currents, while KF neurons receiving excitatory NAergic input showed minimal opioid sensitivity. To assess the behavioral role of glutamate release from all catecholaminergic neurons, we compared breathing in awake VGluT2fl/fl::TH-Cre mice (lacking VGluT2 in tyrosine hydroxylase-positive neurons) to control littermates and TH-Cre hemizygous mice using whole-body plethysmography. The conditional VGluT2 knockout mice exhibited prolonged inspiratory duration, increased tidal volume, and reduced respiratory rate during baseline breathing, with state-dependent differences emerging during hypercapnia. Systemic morphine administration diminished these genotype differences, and machine learning analysis using dynamic time warping confirmed that genotype-specific breathing patterns were distinguishable at baseline, but not after morphine. These findings demonstrate that glutamate co-release from catecholaminergic neurons modulates respiratory patterning in a state-dependent manner and is selectively vulnerable to opioid inhibition.

neuroscience↗

bioRxiv2023

The LRRK2 kinase substrates Rab8a and Rab10 contribute complementary but distinct disease-relevant phenotypes in human neurons

Mutations in the LRRK2 gene cause familial Parkinsons disease presenting with pleomorphic neuropathology that can involve -synuclein or tau accumulation. LRRK2 mutations are thought to converge toward a pathogenic increase in LRRK2 kinase activity. A subset of small Rab GTPases have been identified as LRRK2 substrates, with LRRK2-dependent phosphorylation resulting in Rab inactivation. We used CRISPR/Cas9 genome editing to generate a novel series of isogenic iPSC lines deficient in the two most well validated LRRK2 substrates, Rab8a and Rab10, from two independent, deeply phenotyped healthy control lines. Thorough characterization of NGN2-induced neurons revealed divergent effects of Rab8a and Rab10 deficiency on lysosomal pH, LAMP1 association with Golgi, -synuclein insolubility and tau phosphorylation, while parallel effects on lysosomal numbers and Golgi clustering were observed. Our data demonstrate largely antagonistic effects of genetic Rab8a or Rab10 inactivation which provide discrete insight into the pathologic features of their biochemical inactivation by pathogenic LRRK2 mutation. HighlightsO_LIRab8a and Rab10 deficiency induce lysosomal and Golgi defects C_LIO_LIRab8a and Rab10 deficiency induce opposing effects on lysosomal pH C_LIO_LIRab8a KO and Rab10 KO neurons show divergent effects on synuclein and tau proteostasis C_LIO_LIInactivation of different Rab GTPases can induce distinct disease-relevant phenotypes C_LI

neuroscience↗