Cerebral sympatholysis: experiments on < em > in vivo < /em > cerebrovascular regulation and < em > ex vivo < /em > cerebral vasomotor control

This study tested the hypothesis that application or removal of a cognitive task during a cold pressor test (CPT) would attenuate and restore decreases in cerebrovascular conductance (CVC), respectively. Middle cerebral artery blood velocity (transcranial Doppler) and mean arterial pressure (finger photoplethysmography) were examined in healthy adults (n=16; 8 F and 8 M) who completed a control CPT, followed by a CPT coupled with a cognitive task administered either A) 30 s after the onset of the CPT and for the duration of the CPT or B) at the onset of the CPT and terminated 30 s prior to the end of the CPT (condition order was counterbalanced). The major finding was that the CPT decreased the index of CVC, and such decreases were abolished when a cognitive task was completed concurrently and restored when the cognitive task was removed. As a secondary experiment, vasomotor interactions between sympathetic transduction pathways (α1 adrenergic and Y1 peptidergic) and compounds implicated in cerebral blood flow control (adenosine, and adenosine triphosphate (ATP)) were explored in isolated porcine cerebral arteries (wire myography). The data reveal α1 receptor agonism potentiated vasorelaxation modestly in response to adenosine, and pre-exposure to ATP attenuated contractile responses to α1 agonism. Overall, the data suggest a cognitive task attenuates decreases in CVC during sympatho-excitation, possibly related to an interaction between purinergic and α1-adrenergic signa...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Source Type: research