Early Onset of Ventilatory and Airway Response to Hypercapnia is Mediated by Medullary 5-HT1A Receptors in Infant Rats

Medullary 5-hydroxytryptamine (5-HT) neurons are involved in ventilatory responses to hypercapnia. Underdeveloped medullary 5-HT neurons and reduced 5-HT1A receptor binding activity in the dorsomedial medulla oblongata (DMM) have been found in infants with sudden infant death syndrome (SIDS). The DMM includes the solitary tract nucleus, which receives primary afferent inputs from the lung, and the hypoglossal nucleus, which affects genioglossal muscle tone. We hypothesized that hypercapnia would elicit 5-HT release in the DMM and that local 5-HT1A receptors would affect ventilatory and airway responses to hypercapnia. This hypothesis was investigated in unanesthetized infant Wistar rats by microdialysis of the DMM coupled with double-chamber plethysmography. After microdialysis probe placement, the rats were acclimatized to the chamber for over 5h, and artificial cerebrospinal fluid (aCSF) or a 5-HT1A receptor antagonist, WAY-100635, was then perfused into the DMM, and extracellular fluid was collected. Respiratory flow curves were recorded while the rats inhaled five concentrations of CO2 in O2 for 10 min each (0% [100% O2], 5%, 7%, 9%, and 0% again). 5-HT concentration was measured using high-performance liquid chromatography with electrochemical detection. 5-HT release in the DMM and hypercapnic ventilatory and airway responses increased dose dependently with CO2 concentration during both aCSF and WAY-100635 perfusion, with no difference between groups. However, early-onset ventilatory and airway responses to hypercapnia were significantly delayed or reduced by WAY-100635 perfusion in the DMM. These results suggest that 5-HT release in the DMM is dependent on hypercapnia, while early ventilatory and airway responses to hypercapnia are mediated by 5-HT1A receptors in the DMM. Blunted early onset of hypercapnic ventilatory and airway responses may be one cause of SIDS

Irregular atrial flutter following pulmonary vein isolation for persistent atrial fibrillation

AbstractA 65-year-old man with a history of refractory paroxysmal atrial fibrillation (AF) underwent catheter ablation for persistent AF lasting 2 months. AF was not terminated after complete isolation of the 4 pulmonary veins (PV). Instead, it was transformed to a sustained atrial tachyarrhythmia with beat-to-beat variability in the atrial cycle length. A 12-lead electrocardiogram during tachycardia showed negative flutter-like waves in the inferior leads. Entrainment pacing along the tricuspid annulus confirmed the diagnosis of irregular cavotricuspid isthmus (CTI)-dependent typical atrial flutter (AFL). Linear ablation of the CTI terminated AFL and restored sinus rhythm

Antarctic Study on Tropospheric Aerosol and Snow Chemistry (ASTASC) in JARE Phase X

The Tenth Symposium on Polar Science/Special session: [S] Future plan of Antarctic research: Towards phase X of the Japanese Antarctic Research Project (2022-2028) and beyond, Tue. 3 Dec. / Entrance Hall (1st floor) at National Institute of Polar Research (NIPR

Long-term field experiment for detection and study of climate change in East Antarctica

第6回極域科学シンポジウム[OM] 極域気水圏11月16日（月）　統計数理研究所 セミナー室2（D304