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Parasympathetic Cholinergic Vasodilator Mechanism in the Terminal Liver Microcirculation in Rats
Author(s) -
Koo Anthony,
Liang Isabella Y. S.
Publication year - 1979
Publication title -
quarterly journal of experimental physiology and cognate medical sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0033-5541
DOI - 10.1113/expphysiol.1979.sp002468
Subject(s) - acetylcholine , atropine , physostigmine , cholinergic , stimulation , vagus nerve , endocrinology , medicine , chemistry , parasympathetic nervous system , vasodilation , vagus nerve stimulation , autonomic nervous system , heart rate , blood pressure
Changes in the diameter of liver sinusoids were studied by an intravital television microscope method in pentobarbital-anaesthetized rats. Dilatation of liver sinusoids was observed during parasympathetic neural stimulation and during acetylcholine administration. Frequency-dependent stimulation-effect relationships were obtained by electrical excitation of intact vagus nerves at supramaximal intensity from 2 to 8 Hz. Acetylcholine concentration-effect relationships were also obtained by intraportal venous infusions of acetylcholine 30 microliter for 5 s from 10(-9) to 10(-2) mol.1(-1). Systemic cholinergic receptor blockade with atropine (1 mg.kg-1) markedly reduced dilatation of liver sinusoids produced by both vagus nerve stimulation and acetylcholine administration. Changes in diameter of liver sinusoids with frequency of neural stimulation and with concentration of administered acetylcholine were also expressed as percentage of observed maximum effect and the respective stimulation-effect curves were constructed such that at a certain percentage of diameter change, the equivalent level of vagus nerve activity was represented by a given concentration of administered acetylcholine. Liver plasma concentration of acetylcholine presumably released during electrical vagal stimulation and reaching liver sinusoids was also estimated and found to be within physiological range. It is therefore proposed that rat liver sinusoids have the capacity for parasympathetic cholinergic vasodilatation.