Hurricanes and other Physiological Stressors: Effects on Phrenic Motor Plasticity

Phrenic long-term facilitation (pLTF) is a form of respiratory motor plasticity elicited by moderate acute intermittent hypoxia (mAIH). Although certain factors such as aging and inflammation undermine AIH-induced pLTF, little is known concerning the effects of physiological stress. Anecdotal evidence from our laboratory suggests that low-frequency vibrations from construction ( e.g. jackhammers) near the animal facility undermine mAIH-induced pLTF and causes unstable phrenic bursting with periodic phrenic nerve “apneas” post-AIH for unknown reasons. In the past 2 years, we identified other sources of stress, such as circadian disruption with similar effects on phrenic nerve activity. Here we report that approaching hurricanes destabilize phrenic nerve activity. Extreme weather events produce low-frequency sound waves ( i.e. infrasound), which induce stress responses in rats and other species; infrasound serves as a signal to ‘flee’ from danger. During the 2024 hurricane season, we tested the hypothesis that hurricanes ±7 days from landfall in Florida: 1) elevate serum corticosterone, 2) undermine pLTF, and 3) destabilize phrenic nerve activity. Anesthetized, vagotomized, paralyzed and ventilated adult (3-4 months) male Sprague-Dawley rats were prepared by 3 investigators, and presented with: 1) mAIH (15,1 min or 3,5 min episodes); 2) mAIH with hypercapnia (mAIHH; 15, 1 min episodes; arterial PCO 2 = 5-10mmHg above baseline); or 3) moderate acute sustained hypoxia (mASH; 1, 20 min hypoxic episode; arterial PO 2 = 40-50mmHg). Regardless of protocol or phase of the diurnal cycle, rats studied ±7 days of landfall for 3 hurricanes (n = 15 rats) expressed minimal pLTF and exhibited periodic phrenic nerve “apneas” during stable baseline conditions post-hypoxia. Control rats studied ±7 days of hurricane landfall that did not receive hypoxia expressed neither pLTF (as expected) nor periodic apneas (n = 4 rats). Serum stress hormones were elevated within ± 7 days of hurricane landfall (Corticosterone: 76.8±5.6 µg/dL) vs control (6.9±1.5 µg/dL, *p<0.001). This finding is consistent with prior observations in circadian disrupted rats. Physiological stressors including approaching hurricanes, nearby construction and circadian disruption appear to increase stress hormones that undermine mAIH-induced pLTF and destabilize baseline phrenic nerve activity regardless of time-of-day or hypoxia protocol used. NIH K99HL175029 (ABM), Parker B. Francis Foundation (ABM), NIH F32HL176048 (ALEB), NIH R01HL149800 (GSM) and NIH R01HL148030 (GSM) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.