Background & Objectives: Many researches have been conducted on autoregulation of cerebral blood flow (CBF), but its possible variations coincidence with postvagal tachycardia have not yet been studied. The present study searched for the effect of this phenomenon on CBF in young and middle-aged persons.

 Methods: 52 healthy volunteers including 13 young males (mean age 23.9±0.8), 13 young females (mean age 24.2±0.7), 13 middle-aged males (mean age 58±0.9) and 13 middle-aged females (mean age 56.4±0.7) went under the study. Flow velocity in middle cerebral artery (MCA) was assessed using transcranial Doppler (TCD) ultrasonography apparatus. Eckberg’s neck suction device was utilized to stimulate carotid baroreceptors. The data were analyzed using Minitab and SPSS software (rel. 10).

 Results: Concomitant to the carotid baroreceptors stimulation there was a significant reduction in heart rate in all groups (p<0.05), but mean cerebral blood flow did not change significantly. After ending the carotid baroreceptors stimulation and concomitant to PVT, mean cerebral blood flow increased in all groups except middle-aged males. This increase in CBF became significant in middle-aged females (p<0.05).

 Conclusion: The results of the present study indicate that cerebral blood flow autoregulation act effectively concomitant to acute stimulation of carotid baroreceptors and this efficacy is maintained until the middle-age, but when faced with PVT, cerebral blood flow autoregulation dose not act effectively.