title: Diving and exercise: the interaction of trigeminal receptors and muscle metaboreceptors on muscle sympathetic nerve activity in humans.
abstract: Swimming involves muscular activity and submersion, creating a conflict of autonomic reflexes elicited by the trigeminal receptors and skeletal muscle afferents. We sought to determine the autonomic cardiovascular responses to separate and concurrent stimulation of the trigeminal cutaneous receptors and metabolically sensitive skeletal muscle afferents (muscle metaboreflex). In eight healthy men (30 ± 2 yr) muscle sympathetic nerve activity (MSNA; microneurography), mean arterial pressure (MAP; Finometer), femoral artery blood flow (duplex Doppler ultrasonography), and femoral vascular conductance (femoral artery blood flow/MAP) were assessed during the following three experimental conditions: 1) facial cooling (trigeminal nerve stimulation), 2) postexercise ischemia (PEI; muscle metaboreflex activation) following isometric handgrip, and 3) trigeminal nerve stimulation with concurrent PEI. Trigeminal nerve stimulation produced significant increases in MSNA total activity (Δ347 ± 167%) and MAP (Δ21 ± 5%) and a reduction in femoral artery vascular conductance (Δ-17 ± 9%). PEI also evoked significant increases in MSNA total activity (Δ234 ± 83%) and MAP (Δ36 ± 4%) and a slight nonsignificant reduction in femoral artery vascular conductance (Δ-9 ± 12%). Trigeminal nerve stimulation with concurrent PEI evoked changes in MSNA total activity (Δ341 ± 96%), MAP (Δ39 ± 4%), and femoral artery vascular conductance (Δ-20 ± 9%) that were similar to those evoked by either separate trigeminal nerve stimulation or separate PEI. Thus, excitatory inputs from the trigeminal nerve and metabolically sensitive skeletal muscle afferents do not summate algebraically in eliciting a MSNA and cardiovascular response but rather exhibit synaptic occlusion, suggesting a high degree of convergent inputs on output neurons.
authors.affiliation: School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom; j.p.fisher@bham.ac.uk.
authors.forename: James P
authors.initials: JP
authors.lastname: Fisher
authors.affiliation: Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil; and.
authors.forename: Igor A
authors.initials: IA
authors.lastname: Fernandes
authors.affiliation: Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil; and.
authors.forename: Thales C
authors.initials: TC
authors.lastname: Barbosa
authors.affiliation: Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil; and.
authors.forename: Eliza
authors.initials: E
authors.lastname: Prodel
authors.affiliation: School of Clinical and Experimental Medicine, College of Medicine and Dentistry, University of Birmingham, Birmingham, United Kingdom.
authors.forename: John H
authors.initials: JH
authors.lastname: Coote
authors.affiliation: Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil; and.
authors.forename: Antonio Claudio L
authors.initials: AC
authors.lastname: Nóbrega
authors.affiliation: Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil; and.
authors.forename: Lauro C
authors.initials: LC
authors.lastname: Vianna
mesh_terms: D000328:Adult; D001794:Blood Pressure; D004242:Diving / Q000502:physiology; D065508:Diving Reflex; D015444:Exercise / Q000502:physiology*; D005263:Femoral Artery / Q000502:physiology; D018737:Hand Strength; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000166:cytology / Q000294:innervation / Q000502:physiology*; D012039:Regional Blood Flow; D011984:Sensory Receptor Cells / Q000502:physiology*; D012881:Skin Temperature; D013564:Sympathetic Nervous System / Q000166:cytology / Q000502:physiology*; D014276:Trigeminal Nerve / Q000166:cytology / Q000502:physiology*
keywords: autonomic; cardiovascular; diving response