A synthesized mouse vasoactive intestinal contractor peptide, which belongs to a novel member of the endothelin family, induced a prolonged contraction in mouse ileum as well as porcine coronary artery in vitro. Studies comparing the effects of vasoactive intestinal contractor and endothelin on different tissues revealed that the maximum ileum contraction of vasoactive intestinal contractor was much higher than that of endothelin in both guinea pig and mouse systems, but that the vasoconstriction activity of vasoactive intestinal contractor was weaker than that of endothelin in porcine artery.These resuts show that vasoactive intestinal contractor might be a novel gastrointestinal hormone.
Abstract-The sympathetic inhibitory mechanism in dog urinary bladder was studied. The bladder contractions induced by electrical stimulation of the pelvic nerve both proximal and distal to the pelvic plexus and by intraarterial administration of tetra methylammonium (TMA) were inhibited by stimulation of the hypogastric nerve and intraarterial injection of catecholamines.The inhibition by hypogastric nerve stimu lation was more potent at the low frequency of pelvic nerve stimulation than at the high frequency. The inhibition of contraction induced by stimulation of the pre-plexal pelvic nerve was antagonized by phentolamine and propranolol, whereas the inhibition of contraction induced by stimulation of the post-plexal pelvic nerve and by TMA treatment were antagonized only by propranolol.It is concluded that inhibition by hypogastric nerve stimulation of bladder contraction induced by pelvic nerve stimulation is composed of two different components.One occurs at the ganglia in the pelvic plexus and is mediated by a-adrenoceptors.The other occurs at the post-plexal pelvic pathway, probably at the ganglia in the bladder wall or on the muscle cells, and is mediated by ~-adrenoceptors.Moreover, the a-adrenergic action facilitated the pelvic nerve excitation in its pathway from the ganglionic cell bodies to the muscle cells.In dogs, the pelvic nerve carries parasympathetic fibres to the urinary bladder via the pelvic plexus located on the lateral surface of the rectum, and its ganglion cells are found in the bladder wall and the plexus (1). Many of these ganglia lie in conjunction with the adrenergic cell clusters and fibres (unpublished data). The present experiments were carried out to determine whether the sympathetic regulatory mechanism which has been found in the superior cervical ganglion (2-4) exists in the bladder ganglion of dogs.
MATERIALS AND METHODSFemale mongrel dogs, weighing 7-15 kg, were anesthetized with 35 mg/kg of i.p. pen tobarbital sodium. The lower abdomen was opened along the midline to fully expose the urinary bladder. A urethral catheter was inserted and secured in place by a ligature around the urethra. The catheter was filled with physiological saline and connected to a pressure transducer (Toyo-Baldwin, LPU-0.1) for recording isometric intravesical pressure developed by the detrusor muscle. The bladder was emptied and then refilled with physiological saline of a volume which caused a resting pressure of about 100 inmH2O. The bladder was carefully packed with a cotton-wool pad soaked in warm saline and kept warm. The ureters were ligated and cut, and the proximal cut end was cannulated with polyethylene
Abstract:Digital radiography (100 pixels/mm2) combined with the technique of 3H-labeled desmethylimipramine deposition was employed to visualize regional blood flow distributions in rabbit left ventricular myocardium. A fluctuated pattern of myocardial flow and its dependence on arterial oxygen tension (PaO2) was evaluated with the coefficient of variation (CV) computed at each step of coarse-graining; flow images were revisualized by increasing pixel area (PA) step by step from 0.01 to 1 mm2. The CV values decreased with hypoxia at all resolution levels, suggesting that there is a vascular regulatory mechanism for making myocardial perfusion uniform in response to decreased PaO2. In both perfusion states, Cl/decreased with increasing PA. The relationship between CV and PA fitted the noninteger power law function, implying an apparent fractality of CV.
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