ISSN:
1432-2013
Keywords:
Mammalian Ventricular Myocardium
;
Cholinergic Innervation
;
Endogenous Acetylcholine
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The effect of endogenous acetylcholine (ACh) on the isometric force of contraction has been investigated on 40 papillary muscles of the cat right ventricle and on 20 strips of the chicken right ventricle. ACh was released from intramural cholinergic nerve endings by high voltage stimulation and simultaneous application of trains of stimuli during the absolute refractory period of the myocardium. In the pharmacologically untreated heart muscle the negative inotropic effect of sndogenous ACh was generally superimposed on the positive inotropic effect of simultaneously released catecholamines. During trains of high voltage stimuli, cat papillary muscles pretreated with reserpine showed a significant reduction in amplitude (average 19%) only if contractility had been increased by previous application of noradrenaline or isoprenaline. With guanethidine pretreatment high voltage stimulation reduced the amplitude significantly by 34%. In ventricular myocardium of chicken the negative inotropic effect of endogenous ACh was more impressive even in the absence of an increased contractility due to catecholamines. It is concluded from the following findings, that the negative inotropic substance is ACh: the negative inotropic effect was intensified by neostigmine and prevented by atropine; liquid, sampled from the bath during trains of high voltage stimuli was able to induce a contracture of frog rectus; under trains of high voltage stimuli the radio-activity in the perfusion liquid of preparations, pretreated with ratio-active ACh, was increased during the wash-out period. Moreover, the existence of cholinergic nerve fibers could be detected in cat papillary muscles as well as in chicken heart preparations by means of histochemical identification.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00586040
