Brain stem serotonin protects blood pressure in neonatal rats exposed to episodic anoxia

Hsiao T. Yang, Kevin J. Cummings
2013 Journal of applied physiology  
Yang HT, Cummings KJ. Brain stem serotonin protects blood pressure in neonatal rats exposed to episodic anoxia. In neonatal rodents, a loss of brain stem serotonin [5-hydroxytryptamine (5-HT)] in utero or at birth compromises anoxia-induced gasping and the recovery of heart rate (HR) and breathing with reoxygenation (i.e., autoresuscitation). How mean arterial pressure (MAP) is influenced after an acute loss of brain stem 5-HT content is unknown. We hypothesized that a loss of 5-HT for ϳ1 day
more » ... uld compromise MAP during episodic anoxia. We injected 6-fluorotryptophan (20 mg/kg ip) into rat pups (postnatal days 9 -10 or 11-13, n ϭ 22 treated, 24 control), causing a ϳ70% loss of brain stem 5-HT. Pups were exposed to a maximum of 15 anoxic episodes, separated by 5 min of room air to allow autoresuscitation. In younger pups, we measured breathing frequency and tidal volume using "head-out" plethysmography and HR from the electrocardiogram. In older pups, we used whole body plethysmography to detect gasping, while monitoring MAP. Gasp latency and the time required for respiratory, HR, and MAP recovery following each episode were determined. Despite normal gasp latency, breathing frequency and a larger tidal volume (P Ͻ 0.001), 5-HT-deficient pups survived onehalf the number of episodes as controls (P Ͻ 0.001). The anoxiainduced decrease in MAP experienced by 5-HT-deficient pups was double that of controls (P ϭ 0.017), despite the same drop in HR (P ϭ 0.48). MAP recovery was delayed ϳ10 s by 5-HT deficiency (P ϭ 0.001). Our data suggest a loss of brain stem 5-HT leads to a pronounced, premature loss of MAP in response to episodic anoxia. These data may help explain why some sudden infant death syndrome cases die from what appears to be cardiovascular collapse during apparent severe hypoxia.
doi:10.1152/japplphysiol.00970.2013 pmid:24136109 fatcat:be6lt6vasregldqpdx3s7uawga