title: Selective α1-adrenergic blockade disturbs the regional distribution of cerebral blood flow during static handgrip exercise.
abstract: Handgrip-induced increases in blood flow through the contralateral artery that supplies the cortical representation of the arm have been hypothesized as a consequence of neurovascular coupling and a resultant metabolic attenuation of sympathetic cerebral vasoconstriction. In contrast, sympathetic restraint, in theory, inhibits changes in perfusion of the cerebral ipsilateral blood vessels. To confirm whether sympathetic nerve activity modulates cerebral blood flow distribution during static handgrip (SHG) exercise, beat-to-beat contra- and ipsilateral internal carotid artery blood flow (ICA; Doppler) and mean arterial pressure (MAP; Finometer) were simultaneously assessed in nine healthy men (27 ± 5 yr), both at rest and during a 2-min SHG bout (30% maximal voluntary contraction), under two experimental conditions: 1) control and 2) α1-adrenergic receptor blockade. End-tidal carbon dioxide (rebreathing system) was clamped throughout the study. SHG induced increases in MAP (+31.4 ± 10.7 mmHg, P < 0.05) and contralateral ICA blood flow (+80.9 ± 62.5 ml/min, P < 0.05), while no changes were observed in the ipsilateral vessel (-9.8 ± 39.3 ml/min, P > 0.05). The reduction in ipsilateral ICA vascular conductance (VC) was greater compared with contralateral ICA (contralateral: -0.8 ± 0.8 vs. ipsilateral: -2.6 ± 1.3 ml·min(-1)·mmHg(-1), P < 0.05). Prazosin was effective to induce α1-blockade since phenylephrine-induced increases in MAP were greatly reduced (P < 0.05). Under α1-adrenergic receptor blockade, SHG evoked smaller MAP responses (+19.4 ± 9.2, P < 0.05) but similar increases in ICAs blood flow (contralateral: +58.4 ± 21.5 vs. ipsilateral: +54.3 ± 46.2 ml/min, P > 0.05) and decreases in VC (contralateral: -0.4 ± 0.7 vs. ipsilateral: -0.4 ± 1.0 ml·min(-1)·mmHg(-1), P > 0.05). These findings indicate a role of sympathetic nerve activity in the regulation of cerebral blood flow distribution during SHG.
authors.affiliation: Laboratory of Exercise Sciences, Department of Physiology and Pharmacology, Fluminense Federal University, Rio de Janeiro, Brazil; and iafernandes@id.uff.br.
authors.forename: Igor A
authors.initials: IA
authors.lastname: Fernandes
authors.affiliation: Laboratory of Exercise Sciences, Department of Physiology and Pharmacology, Fluminense Federal University, Rio de Janeiro, Brazil; and.
authors.forename: João D
authors.initials: JD
authors.lastname: Mattos
authors.affiliation: Laboratory of Exercise Sciences, Department of Physiology and Pharmacology, Fluminense Federal University, Rio de Janeiro, Brazil; and.
authors.forename: Monique O
authors.initials: MO
authors.lastname: Campos
authors.affiliation: Laboratory of Exercise Sciences, Department of Physiology and Pharmacology, Fluminense Federal University, Rio de Janeiro, Brazil; and.
authors.forename: Alessandro C
authors.initials: AC
authors.lastname: Machado
authors.affiliation: Laboratory of Exercise Sciences, Department of Physiology and Pharmacology, Fluminense Federal University, Rio de Janeiro, Brazil; and.
authors.forename: Marcos P
authors.initials: MP
authors.lastname: Rocha
authors.affiliation: Laboratory of Exercise Sciences, Department of Physiology and Pharmacology, Fluminense Federal University, Rio de Janeiro, Brazil; and.
authors.forename: Natalia G
authors.initials: NG
authors.lastname: Rocha
authors.affiliation: Faculty of Physical Education, University of Brasilia, Distrito Federal, Brazil.
authors.forename: Lauro C
authors.initials: LC
authors.lastname: Vianna
authors.affiliation: Laboratory of Exercise Sciences, Department of Physiology and Pharmacology, Fluminense Federal University, Rio de Janeiro, Brazil; and.
authors.forename: Antonio C L
authors.initials: AC
authors.lastname: Nobrega
mesh_terms: D058668:Adrenergic alpha-1 Receptor Antagonists / Q000008:administration & dosage*; D000328:Adult; D062186:Arterial Pressure; D001783:Blood Flow Velocity; D002343:Carotid Artery, Internal / Q000294:innervation*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D005542:Forearm; D018737:Hand Strength; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000294:innervation*; D000069336:Neurovascular Coupling / Q000187:drug effects*; D011224:Prazosin / Q000008:administration & dosage*; D018342:Receptors, Adrenergic, beta-1 / Q000187:drug effects* / Q000378:metabolism; D012039:Regional Blood Flow; D013564:Sympathetic Nervous System / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects*; D055815:Young Adult
chemical_list: C547787:ADRB1 protein, human; D058668:Adrenergic alpha-1 Receptor Antagonists; D018342:Receptors, Adrenergic, beta-1; D011224:Prazosin
keywords: brain; cerebral blood flow; forearm exercise; neurovascular coupling; sympathetic nerve activity