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Role of autoinhibitory feedback in cardiac sympathetic transmission

Journal Article · · Clin. Exp. Hypertens.; (United States)
; ; ; ;
The relationship between two indices of transmitter release measured simultaneously and the frequency of 4 field pulses (0.125-2 Hz) were obtained from superfused guinea pig right atria after labelling with /sup 3/H-noradrenaline. The relationships between /sup 3/H-efflux or rate responses and frequency were hyperbolic. Autoinhibitory feedback did not play a role since phentolamine (1 microM) did not alter the /sup 3/H-efflux or rate responses to 4 field pulses that gave 50-60% of the maximum rate response. In the presence of neuronal uptake block (desipramine (0.1 microM) phentolamine enhanced /sup 3/H-efflux and rate responses to 4 field pulses at all frequencies. In the absence of desipramine prolonged trains of field pulses (8-12 pulses) at low frequency (0.25 Hz) were not sufficient to activate autoinhibitory feedback. At 2 Hz phentolamine enhanced both responses at 12 field pulses. We conclude that in the right atrium autoinhibitory feedback plays little role in the modulation of transmitter release at levels of stimulation that cause 50-60% of maximum tissue response. The presence of neuronal uptake inhibition or high stimulus strengths are necessary to evoke autoinhibitory feedback.
Research Organization:
Baker Medical Research Institute, Prahran, Victoria, Australia
OSTI ID:
6966149
Journal Information:
Clin. Exp. Hypertens.; (United States), Journal Name: Clin. Exp. Hypertens.; (United States) Vol. 6:1-2; ISSN CEHYD
Country of Publication:
United States
Language:
English

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Related Subjects

550101 -- Behavioral Biology-- Tracer Techniques
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59 BASIC BIOLOGICAL SCIENCES
ADRENAL HORMONES
ANIMALS
ANTIDEPRESSANTS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMICAL REACTION KINETICS
BODY
CARDIOTONICS
CARDIOVASCULAR AGENTS
CARDIOVASCULAR SYSTEM
CENTRAL NERVOUS SYSTEM AGENTS
DRUGS
GUINEA PIGS
HEART
HORMONES
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
NEUROREGULATORS
NORADRENALINE
ORGANS
PSYCHOTROPIC DRUGS
REACTION KINETICS
RODENTS
STEROID HORMONES
SYMPATHOLYTICS
SYMPATHOMIMETICS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES