ISSN:1018-1172    

DOI:10.1159/000158675

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158676

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The field stimulation induced release of 3H-norepinephrine (NE) from the isolated portal vein and endogenous NE from the isolated caudal artery and perfused mesenteric arterial bed of spontaneously hypertensive rats (SHR) and age-matched normotensive rats (Wistar-Kyoto or Sprague-Dawley) was studied. There was a significantly greater release of NE from all three preparations obtained from 10- to 12-week-old SHR compared to normotensive animals. In addition, there was a greater release of NE from the caudal artery of 5- to 6-week-old SHR compared to controls. No differences were seen in the evoked release of NE from portal vein or caudal artery obtained from renal or DOCA salt hypertensives compared to vessels obtained from sham controls. Neuropeptide Y (NPY) produced a concentration-dependent decrease in the field stimulation induced release of NE from the perfused mesenteric artery. Low concentrations of NPY decreased while higher concentrations potentiated the increase in perfusion pressure. The NPY induced inhibition of evoked NE release was not altered by α1- or α2-adrenoceptor antagonists while the α1-adrenoceptor antagonist, prazosin, prevented the postjunctional response. These results are consistent with there being an alteration of NE release at the vascular neuroeffector junction in SHR which may contribute to the development or maintenance of hypertension. NPY exerts a modulatory role in noradrenergic transmission at the vascular neuroeffector juncti

ISSN:1018-1172    

DOI:10.1159/000158677

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

There is a substantial body of indirect pharmacologic evidence which has been interpreted as indicating that presynaptic receptor-mediated modulation of noradrenergic vascular neurotransmission is altered in the mesenteric vasculature of SHR. Enhanced release of either total 3H or 3H-NE after prelabeling with 3H-NE has been demonstrated to occur from the mesenteric vasculature of SHR after administration of isoproterenol or angiotensin II. However, evidence has now been obtained in the mesenteric vasculature demonstrating that there are no differences in the release of endogenous NE from adult SHR preparations versus that from adult WKY preparations.

ISSN:1018-1172    

DOI:10.1159/000158678

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Okadaic acid (OA) isolated from black sponge (Halichondria) caused tonic contractions of human umbilical arteries and rabbit aorta both in the presence and absence of Ca2+. This tonic contraction was not affected by Ca2+ chelator, Ca2+ entry blockers and La3+. In addition, the antagonists of alpha-adrenoceptors, histamine, serotonin and ACh receptors had no effect on the OA-induced contraction. High K, ouabain and indomethacin failed to inhibit the response to OA. However, the combination of anaerobic conditions and absence of glucose abolished the response to OA. OA had no effect on the myosin B ATPase and saponin-treated skinned fibers of rabbit aorta. The contractile action of OA may not also be related to calmodulin-related PDE and mitochondrial respiration. In conclusion, although the precise mode of action is not evident at the present time, OA, in its unique pharmacological action – that of producing sustained contraction independent of extracellular Ca2+ -may alter the handling of Ca2+ to intracellular store site

ISSN:1018-1172    

DOI:10.1159/000158679

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

A review of research on the relationship between the regulation of cellular sensitivity to drugs and transmitters and membrane potential is presented, with an emphasis on experiments with the rabbit saphenous artery. Chronic depression of the adrenergic innervation to the saphenous artery induces an adaptive and nonspecific increase in sensitivity which appears with a delay of 3 days. Coincident with the supersensitivity, the smooth muscle cells undergo a partial depolarization which brings the resting potential closer to the threshold potential for contraction. The evidence is that the depolarization is due to the loss of electrogenic Na+, K+ pumping and is the primary factor responsible for the supersensitivity.

ISSN:1018-1172    

DOI:10.1159/000158680

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The adrenergic neuroeffector mechanism of blood vessels in Fischer 344 rats was studied from young adulthood to senescence. Norepinephrine (NE) content is maintained through senescence in all veins studied as well as in the superior mesenteric artery. In contrast, NE content declined at 27 months of age in all other arteries studied. Nevertheless, vascular reactivity in vitro to adrenergic nerve stimulation and to NE was well maintained. As to beta-adrenergic responsiveness, this showed a marked decline in arteries from 1 to 6 months of age, but was unchanged in the jugular vein from 3 to 27 months. Overall, then, adrenergic responsiveness of vascular smooth muscle is well maintained in aged rats. However, this study focuses on a discrete aspect of blood pressure control in a species where atherosclerosis is not prominent. Alterations at other sites could be responsible for changes in the overall function of adrenergic cardiovascular control.

ISSN:1018-1172    

DOI:10.1159/000158681

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Endothelial thromboxane A2 (TXA2) in maintaining the resting tone and producing the contractile response to acetylcholine (ACh) and arachidonic acid was studied in canine cerebral artery. The spontaneous release of TXB2 from cerebral artery was about tenfold higher than that of coronary, mesenteric and saphenous arteries. The resting tone, the release of TXB2 and the contraction produced by arachidonic acid were decreased by the presence of cyclooxygenase inhibitor, TXA2 synthetase inhibitor, TXA2 antagonist and rubbing of the luminal side of preparations. The contraction produced by ACh was inhibited by the presence of the above inhibitors and rubbing of the preparations without decreasing the release of TXB2. These results suggest that the resting tone of canine cerebral artery and the contractile response to arachidonic acid are related to activation of TXA2 synthesis in the endothelium.

ISSN:1018-1172    

DOI:10.1159/000158682

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Recent studies from several laboratories have suggested that the cardiovascular system may be considered a new target organ system for parathyroid hormone (PTH). PTH caused a sharp, dose-dependent reduction in blood pressure of several mammalian models. This hypotensive response was mediated by direct interaction of PTH with the vascular smooth muscle of arteries and resistance vascular beds. Increases in intracellular cyclic AMP concentrations were temporally and quantitatively correlated with smooth muscle relaxation by PTH. Direct (nonreflex) positive inotropic and chronotropic effects have been observed in cardiac tissue after treatment with PTH. Considering these and other observations, a physiological role for PTH as a homeostatic regulator of the cardiovascular system may be speculated.

ISSN:1018-1172    

DOI:10.1159/000158683

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Electrical field stimulation of the rat caudal artery (0.5-ms pulses at 8 Hz for 3 min) results in the release of norepinephrine (quantified by HPLC-electrochemical detection) and adenyl purines including ATP, ADP and AMP (quantified by HPLC-fluorescence detection). The amount of ATP released from the tissue exceeded the amount of norepinephrine. Because postjunctional α1-adrenoceptor stimulation with methoxamine also causes release of ATP, both neuronal and extraneuronal sites may contribute to the overflow of ATP. Results with the α1-adrenoceptor antagonist prazosin lend support to this notion. Prazosin (10–6M) completely blocked the release of ATP by methoxamine but only partially reduced the release of ATP by field stimulat

ISSN:1018-1172    

DOI:10.1159/000158684

出版商:S. Karger AG    

年代:1987

数据来源: Karger