Local and distant manifestations of the venoarteriolar reflex

Abstract

The venoarteriolar reflex (VAR) is considered a good example of local vasomotor control depending on both myogenic and neural mechanisms. The presence of a neural component suggests generalized effects in‐so‐far as the sensory input may reach systemic vasomotor regulatory centers. The objective of the present study was to find out whether such distant effects are really present. In order to do this we compared the changes in the blood flow of the contralateral arm while inducing the VAR in the ipsilateral one. The VAR was elicited by a local orthostatic stress – lowering of the ipsilateral arm 40 cm below heart level. During the procedure the subject was in supine position with the other arm at heart level. Index finger photoplethysmography from both arms was simultaneously recorded before, during, and after the orthostatic stimulation using PPG100C transducer coupled to a TSD200 amplifier (Biopac Systems Inc.). Precordial single channel ECG was also recorded. The VAR was evaluated by the changes in the amplitude of the photoplethysmography.The results showed the existence of contralateral VAR although less pronounced and more transient than the ipsilateral one. It is concluded that the local orthostatic stress does evoke more widespread changes affecting distant vascular beds.The present study was supported by the Research Committee of Saba University School of Medicine.