Inhibition of muscle sympathetic nerve activity during yawning.
Yawning is a complex event that depends largely on the autonomic nervous system. Microneurographic techniques were used to study the mechanism involved in yawning. A series of spontaneous yawns displayed by a healthy 39-year-old male offered us the opportunity to study the muscle sympathetic nerve activity (MSNA) during this phenomenon. It was found that 2 s of yawning inhibited the MSNA recorded at the right peroneal nerve in the lateral knee area, while 3 s of slow expiration succeeding a yawn provoked an MSNA discharge. Blood pressure decreased with each slow expiration by 5-6 mmHg, and increased again with the renewed MSNA discharge. We conclude that yawning is associated with a sympathetic suppression that favours a parasympathetic dominance, as indicated by the MSNA and the decrease in blood pressure. The slow expiration following a yawn is associated with a sympathetic activation marked by an MSNA discharge and an increase in blood pressure.
Sleep Medicine Institute, Sheba Medical Centre, Sackler School of Medicine, Tel Aviv University, Israel.
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D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D006801:Humans; D008297:Male; D008839:Microelectrodes; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000502:physiology; D015656:Respiratory Mechanics / Q000502:physiology; D016683:Supine Position / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*; D015000:Yawning / Q000502:physiology*