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.
J. J. M. Askenasy1 
 and N. Askenasy2
| (1)  | Sleep Medicine Institute, Sheba Medical Centre (affiliated to Sackler School of Medicine, Tel Aviv University), Israel | 
| (2)  | Department of Internal Medicine E, Asaf Harofeh Medical Centre, Israel | 
| (3)  | Sleep Medicine Institute, Sheba Medical Centre, 52621 Tel Hashomer, Israel | 
Received: 15 November 1995  Accepted: 26 April 1996