Prolongation of the laryngeal chemoreflex after inhibition of the rostral ventral medulla in piglets: a role in SIDS?
We tested the hypothesis that inhibition of neurons within the rostral ventral medulla (RVM) would prolong the laryngeal chemoreflex (LCR), a putative stimulus in the sudden infant death syndrome (SIDS). We studied the LCR in 19 piglets, age 3-16 days, by injecting 0.05 ml of saline or water into the larynx during wakefulness, non-rapid eye movement (NREM) sleep, and REM sleep, before and after 1 or 10 mM muscimol dialysis in the RVM. Muscimol prolonged the LCR (P < 0.05), and the prolongation was greater when the LCR was stimulated with water compared with saline (P < 0.02). The LCR was longer during NREM sleep than during wakefulness and longest during REM sleep (REM compared with wakefulness). Muscimol had no effect on the likelihood of arousal from sleep after LCR stimulation. We conclude that the RVM provides a tonic facilitatory drive to ventilation that limits the duration of the LCR, and loss of this drive may contribute to the SIDS when combined with stimuli that inhibit respiration.
Van Der Velde
Liesbeth
L
Departments of Physiology, Medicine, and Pediatrics, Dartmouth Medical School, Lebanon, New Hampshire 03756, USA.
Curran
Aidan K
AK
Filiano
James J
JJ
Darnall
Robert A
RA
Bartlett
Donald
D
Leiter
J C
JC
D000818:Animals; D000831:Animals, Newborn; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D018755:GABA Agonists / Q000494:pharmacology; D006801:Humans; D007223:Infant; D007830:Larynx / Q000187:drug effects*; D008526:Medulla Oblongata / Q000187:drug effects*; D017551:Microdialysis; D009118:Muscimol / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects; D017286:Polysomnography / Q000187:drug effects; D012018:Reflex / Q000187:drug effects*; D015656:Respiratory Mechanics / Q000187:drug effects; D012890:Sleep / Q000502:physiology; D012895:Sleep, REM / Q000502:physiology; D013238:Stereotaxic Techniques; D013398:Sudden Infant Death / Q000473:pathology*; D013552:Swine
D018755:GABA Agonists; D009118:Muscimol