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Titolo:
Graded and dynamic reflex summation of myelinated and unmyelinated rat aortic baroreceptors
Autore:
Fan, W; Schild, JH; Andresen, MC;
Indirizzi:
Oregon Hlth Sci Univ, Dept Physiol & Pharmacol, Portland, OR 97201 USA Oregon Hlth Sci Univ Portland OR USA 97201 rmacol, Portland, OR 97201 USA
Titolo Testata:
AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY
fascicolo: 3, volume: 46, anno: 1999,
pagine: R748 - R756
SICI:
0363-6119(199909)46:3<R748:GADRSO>2.0.ZU;2-A
Fonte:
ISI
Lingua:
ENG
Soggetto:
GLOSSOPHARYNGEAL SENSORY NEURONS; CAROTID-SINUS BARORECEPTORS; NUCLEUS-TRACTUS-SOLITARIUS; SYMPATHETIC REFLEX; COEXISTENCE; RECEPTORS; DISCHARGE; VAGAL;
Keywords:
baroreflex; C fiber; anodal block;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
37
Recensione:
Indirizzi per estratti:
Indirizzo: Andresen, MC Oregon Hlth Sci Univ, Dept Physiol & Pharmacol, L334, Portland, OR 97201 USA Oregon Hlth Sci Univ L334 Portland OR USA 97201 OR 97201 USA
Citazione:
W. Fan et al., "Graded and dynamic reflex summation of myelinated and unmyelinated rat aortic baroreceptors", AM J P-REG, 46(3), 1999, pp. R748-R756

Abstract

Unmyelinated (C) and myelinated (A) baroreceptor (BR) axons are present inrat aortic depressor nerve (ADN). With graded ADN electrical activation and anodal conduction blockade, reflex responses in anesthetized rats were assessed as changes in mean arterial pressure (MAP) and heart rate (HR). We tested the hypothesis that C-type BR inputs are effective at low frequenciesbecause they outnumber A-type. Anodal current (I-an) reversibly eliminatedall MAP and HR responses to A-selective stimuli. High intensities activated all ADN axone (A + C) and decreased MAP at lower frequencies (<10 Hz) than were effective with A-selective stimulation. I-an reduced only MAP responses to >10-Hz ADN stimulation. Burst patterns significantly augmented A- but not C-selective reflex responses despite identical numbers of shocks per second. A-selective stimuli failed to evoke significant bradycardia even at200 Hz. Maximum intensity stimuli plus I-an (C selective) evoked less bradycardia than without I-an (A+C), indicating supra-additive summation unlikethe occlusive summation for MAP responses. However, activation of reduced numbers of C-type BRs with all A-type BRs suggests a strong A to C interaction in reflex bradycardia responses. Surprisingly, I-an block of A-type conduction eliminated all reflex bradycardia at such submaximal intensities despite C conduction and depressor responses. A- and C-type BRs act synergistically, and A-type activity is absolutely required in cardiac but not in depressor pathways. Thus greater numbers do not appear to account for C-type BR efficacy, and critical interactions between these two sensory subtypes appear to occur differentially across cardiac and systemic baroreflex effector pathways.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 12/07/20 alle ore 12:45:30