ISSN:
1432-1912
Keywords:
Human Ventricular Myocardium
;
Endogenous Acetylcholine
;
Hemicholinium
;
Tetrodotoxin
;
Parasympathetic Nerve Fibres
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The release of endogenous acetylcholine (ACh) has been investigated in 9 human papillary muscles. In the isolated preparation, transmitter substances were released by high voltage stimulation and simultaneous application of trains of stimuli during the abolute refractory period of the myocardium. In the pharmacologically untreatet human heart muscle the negative inotropic effect of ACh was superimposed on the positive inotropic effect of simultaneously released catecholamines. After treatment with guanethidine, high voltage stimulation reduced the amplitude of isometric contraction by an average of 14%. After contractility had been increased by noradrenaline, isoprenaline, orciprenaline or theophylline high voltage stimulation reduced the amplitude of contraction by 23%. These negative inotropic effects were increased up to 47% by neostigmine, diminished by hemicholinium and prevented by atropine, Blockade of intramural nerve endings by tetrodotoxin abolished completely the positive as well as negative inotropic effects of high voltage stimuli. These findings indicate the possibility of a release of endogenous ACh from intramural nerve endings also in human ventricular myocardium. The negative inotropic effect of endogenous ACh is most pronounced during positive inotropic effects of sympathominetic agents or of theophylline.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00501193
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