Relative contributions of sympathetic, cholinergic, and myogenic mechanisms to cerebral autoregulation.
OBJECTIVE
Prior work aimed at improving our understanding of human cerebral autoregulation has explored individual physiological mechanisms of autoregulation in isolation, but none has attempted to consolidate the individual roles of these mechanisms into a comprehensive model of the overall cerebral pressure-flow relationship.


METHODS
We retrospectively analyzed this relationship before and after pharmacological blockade of α-adrenergic-, muscarinic-, and calcium channel-mediated mechanisms in 43 healthy volunteers to determine the relative contributions of the sympathetic, cholinergic, and myogenic controllers to cerebral autoregulation. Projection pursuit regression was used to assess the effect of pharmacological blockade on the cerebral pressure-flow relationship. Subsequently, ANCOVA decomposition was used to determine the cumulative effect of these 3 mechanisms on cerebral autoregulation and whether they can fully explain it.


RESULTS
Sympathetic, cholinergic, and myogenic mechanisms together accounted for 62% of the cerebral pressure-flow relationship (P<0.05), with significant and distinct contributions from each of the 3 effectors. ANCOVA decomposition demonstrated that myogenic effectors were the largest determinant of the cerebral pressure-flow relationship, but their effect was outside of the autoregulatory region where neurogenic control appeared prepotent.


CONCLUSIONS
Our results suggest that myogenic effects occur outside the active region of autoregulation, whereas neurogenic influences are largely responsible for cerebral blood flow control within it. However, our model of cerebral autoregulation left 38% of the cerebral pressure-flow relationship unexplained, suggesting that there are other physiological mechanisms that contribute to cerebral autoregulation.
From the Cardiovascular Research Laboratory, Spaulding Rehabilitation Hospital, Boston, MA (J.W.H., C.O.T.); and Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA (C.O.T.).
J W
JW
Hamner
From the Cardiovascular Research Laboratory, Spaulding Rehabilitation Hospital, Boston, MA (J.W.H., C.O.T.); and Department of Physical Medicine and Rehabilitation, Harvard Medical School, Boston, MA (C.O.T.). cotan@partners.org.
Can Ozan
CO
Tan
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage; D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology / Q000528:radiation effects; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002121:Calcium Channel Blockers / Q000008:administration & dosage; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D018680:Cholinergic Antagonists / Q000008:administration & dosage; D005260:Female; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008297:Male; D008955:Models, Cardiovascular; D018727:Muscarinic Antagonists / Q000008:administration & dosage; D013564:Sympathetic Nervous System / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D002121:Calcium Channel Blockers; D018680:Cholinergic Antagonists; D018727:Muscarinic Antagonists
autonomic pathways; cerebrovascular circulation; stroke