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Reappraisal of Inhibition and Summation with a Single Conditioning Stimulus in Man
Author(s) -
SAIHARA SHINICHIRO,
INOUE HIROSHI,
TODA IKU,
USUI MASAHIRO,
SUGIMOTO TSUNEAKI
Publication year - 1990
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1990.tb05064.x
Subject(s) - stimulus (psychology) , medicine , conditioning , audiology , refractory period , neutral stimulus , summation , anesthesia , stimulus control , psychology , stimulation , cognitive psychology , mathematics , statistics , nicotine
A noncapturing conditioning stimulus is known to exert inhibitory effect on a subsequent supru‐threshold stimulus, while summation occurs rarely in man. The present study was conducted to revaluate whether conditioning stimulus at a relatively low intensity produced inhibition and summation in man. Thirteen patients with various arrhythmias, 47 ± 19 years old, were studied. Basic ventricular driving stimuli (S 1 S 1 = 600 msec), a conditioning stimulus (Sc), and extrastimulus (S 2 ) were introduced from a catheter electrode. Sc at an intensity of twice the late diastolic threshold inhibited suprathreshold S 2 from evoking a response in all 13 patients. The ScS 2 interval producing inhibition was from 11 ± 4 to 38 ± 26 msec. When Sc preceded S 2 by 5 msec, effective refractory period was shortened by 16 ± 7 msec in 7 of 23 patients, a phenomenon of summation. The present study demonstrates that inhibition and summation are common phenomena with a single conditioning stimulus at relatively low intensities.