摘要:

Intact segments of mesenteric resistance arteries (200 µm) from 5-month-old spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats were tested for norepinephrine (NE) sensitivity. Dose-response curves were obtained both before and after adrenergic denervation produced by short-term, in vitro, 6-hydroxydopamine (6-OHDA) treatment. NE sensitivities of innervated vessels were the same in SHR and WKY rats, however, after 6-OHDA, not only did both ED50s show significant decreases (8.7- and 3.8-fold, respectively), but the ED50 of SHR vessels was half that of WKY (NE sensitivity increased twofold). In addition there was a 33% increase in wall tension generated in response to maximum NE stimulation, and a 44% increase in neuronal NE uptake in the SHR vessels. These results show that several important alterations have occurred in resistance vessels from SHR rats in the established phase of hypertension. The relationship of the increase in neuronal uptake to the increased total peripheral resistance and increased vascular reactivity commonly seen in SHR perfused beds and whole animals is unknown. However, the increases in NE sensitivity and in maximum NE wall tension could contribute to increases in both of these characteristics

ISSN:1018-1172    

DOI:10.1159/000158230

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Longitudinal strips isolated from canine distributing muscular arteries were relaxed by noradrenaline and contracted by papaverine. This paradoxical relaxation and contraction may be due to a helical and circular arrangement of smooth muscle in the wall which is incompressible. Various vasoconstrictive agents, including noradrenaline, produced a circumferential contraction and longitudinal relaxation in muscular arteries. Vasodilator agents produced the opposite effect. The direction and magnitude of response of a helical strip to a vasoactive substance depended upon its sectioning angle from the transverse axis of the vessel.

ISSN:1018-1172    

DOI:10.1159/000158231

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The reactivity to sympathetic nerve activation and the metabolism of 3H-norepinephrine were compared in isolated saphenous veins of dogs and rabbits. The veins of both species were equally sensitive to electrical stimulation, but the magnitude of the contractile responses to such stimulation was larger in the dog. The response to depolarization of the adrenergic nerve endings by high K+ solutions was depressed by phentolamine to a greater extent in the dog than in the rabbit vein. After incubation with 3H-norepinephrine, electrical stimulation caused a greater evoked release of tritiated transmitter in the dog than in the rabbit veins. These experiments suggest that the former are more densely innervated. In resting conditions and during electrical stimulation, the dog veins and the rabbit veins degraded 3H norepinephrine in a different way. In both species, neuronal uptake appeared to be of minor importance in the disposition of 3H-norepinephrine released during continuous electrical stimulation. The reactivity to exogenous catecholamines and acetylcholine were also compared in both veins. The apparent sensitivity to exogenous norepinephrine was greater in rabbit than in dog veins. This difference disappeared after inhibition of neuronal uptake with cocaine, suggesting that it is due to the difference in density of adrenergic innervation. There was no interspecies difference in the sensitivity of the β-adrenoceptors, but the maximal effect of β-adrenergic activation by isoproterenol was larger in the dog than in the rabbit veins. In both species acetylcholine caused inhibition of adrenergic neurotransmission, and direct activation of the venous smooth muscle cells. As regards the latter effect, dog veins were less sensitive to acetylcholine but their response was stronger than that of rabbit veins. These results suggest that the density of adrenergic innervation modulates mainly the apparent sensitivity of the venous smooth muscle to α-adrenergic activati

ISSN:1018-1172    

DOI:10.1159/000158232

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The sudanophilic lesions around the aortic ostia of 10 fetuses, 10 newborns and 10 children aged up to 1 year were studied using a polar coordinate mapping method. The periorificial sudanophilic lesions develop initially distal to the orifices and show a continuous increase with age in percentage and extent. In children the lesions nearly completely surround all the ostia with a significant distal peak. There was no sex difference; the involvement of the right and left side was comparable. The comparison of the morphological data from the parents and children with anamnestics showed no relationship.

ISSN:1018-1172    

DOI:10.1159/000158233

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Use of the method of transmural nerve stimulation depends on the assumption that stimulation parameters can be chosen to selectively and maximally activate nerves without stimulating vascular smooth muscle directly. When commercial stimulators are used with low impedance electrodes, it may not be possible to validate this assumption, due to the limited current output in this situation. To circumvent this limitation a coupling device which provides a very low source impedance to the electrodes is described. Using this device in experiments on preparations of rabbit ear artery, we have demonstrated that it is possible to selectively activate nerves, without stimulating smooth muscle directly. Adrenergic nerve activation was blocked with guanethidine, phentolamine or tetrodotoxin, while responses to direct smooth muscle activation persist in the presence of these drugs. Appropriate parameters for supramaximal nerve stimulation vary with the type of preparation and electrode arrangement. The possibility of variation with tissue and species is also discussed.

ISSN:1018-1172    

DOI:10.1159/000158234

出版商:S. Karger AG    

年代:1980

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158235

出版商:S. Karger AG    

年代:1980

数据来源: Karger