ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY This report reviews a number of significant developments in the fields of noradrenergic transmission and adrenergic receptors which suggest that, hi addition to the classical postsynaptic adrenoceptors, there are also presynaptic adrenoceptors that help modulate tbe release of norepinephrine (NE) from peripheral as well as central noradrenergic nerve endings during nerve stimulation. In particular, stimulation of presynaptic a-adrenoceptors reduces this release of transmitter and tbe reverse is observed after blockade of these receptors. Clearcut pharmacological differences exist between the postsynaptic aradrenoceptors that mediate the responses of certain organs and the presynaptic aradrenoceptors that modulate the NE release during nerve stimulation. Therefore, subdassification of a-adrenoceptors into a, and a, subtypes is warranted but must be considered to be independent of the anatomical location of these receptors.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY The role of the kidney in handling the biologically acthe, nnconjugated endogenous catecholamines epinephrine (E), noreptnephrine (NE), dopamlne (DA), and the O-methylated metabolite of NE, normetanephrine (NM), was studied in the anesthetized dog before and after Toloroe expansion with iaotonk saline by measuring renal arterial deUrery, urinary excretion rate, and renal Tenons return of these materials. Net turnover in the renal metabolic compartment was estimated by comparing arterial delivery to urinary excretion and renal Tenons return. The kidney extracted E and produced NE, DA, and NM before and after Tolume expansion. After Tolume expansion a significant decrease in the extraction of E, an Increase in the production of DA, and no change in the production of NE or NM was seen. Clearance of catecbolamlnes and NM through the kidneys appeared to increase with Tolume expansion. The clearance of DA exceeded the clearance of creatinine (Cr) after volume expansion, while the clearance of NM exceeded that of Cr before and after volume expansion, indicating that urinary DA and NM are derived, in part, from processes other than glomerular filtration. These observations suggest an important role for the kidney in the modulation of the excretion of catecholamines and metabolites. This role must be considered before the urinary excretion rate of N, E, DA, and NM can be related to generalized sympathetic function. The observed increases in renal DA production after saline infusion suggest a possible natriuretic function of intrarenal DA.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY Bromocriptine (Br) was used to test the hypothesis that central dopaminergic mechanisms modulate sympathetic nerve tone, and that when dopaminergic control is deficient there may result enhanced noradrenergic activity and elevated blood pressure (BP) in some patients with primary hypertension. Seven hypertensive patients (age 29 ± 3 years) were studied after a single oral dose of Br (2.5-5.0 mg) and after 1 week of treatment with Br (5-15 mg/day). The data were compared to those obtained during respective placebo periods. The Br reduced systolic blood pressure (SBP) and diastolic blood pressure (DBP) during supine, sitting, and standing positions and mild mental stress but not during isometric handgrip exercise. Orthostatic hypotension occurred in all patients after the first dose of Br but was present only In one patient after 1 week of treatment. Pretreatment levels of plasma norepinephrine (NE) in supine and standing positions were elevated as compared to previously obtained data of normal controls. After 1 week of Br therapy, plasma NE was reduced 40% to 50% in supine, sitting, and standing positions, and during isometric handgrip exercise (p< 0.05). Plasma NE after a single dose of Br was not different from that found after 1 week of the drug. Excretion rates of urinary NE and normetanephrine (NM) were lower (p< 0.002 andp< 0.005 respectively) during Br as compared to pretreatment values. Sodium excretion tended to be higher and plasma renin activity (PRA) lower after 1 week of Br, but the differences were not significant. Dopaminergic stimulation by Br, probably central in location, reduces sympathetic outflow and thereby might contribute to lowering of BP in primary hypertension. These findings support the hypothesis that reduced central dopaminergic activity may be a factor in the cause and maintenance of primary hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY The cardiovascular effects of opioid peptides have been studied. Leudne-enkephalln (Leu- ENK) produced blood pressure (BP) increases following administration into the lateral brain ventricles (i.v.t.), into the cisterns magna (i.e.!.), and following Intravenous (I.Y.) administration. Heart rate (HR) increases were observed following all routes of administration (threshold for BP and HR effects at 03 nmole, maximum at 360 nmoles). The cardiovascular effects were independent of generalized seizures, which may occur at higher doses of enkephaiins (ENK).

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY Although evidence exists for exaggerated sympathetic nervous system activity in spontaneously hypertensive rats (SHR), there are no studies in conscious animals that directly demonstrate that this increased activity is functionally involved in the elevated vascular resistance of these animals. In our present study, 8-week-old and 13-week-old SHR and Wistar Kyoto controls (WKY) were chronically Instrumented with arterial and venous catheters and miniaturized pulsed Doppler flow probes on the renal and mesenteric arteries and lower abdominal aorta. While the rats were conscious and unrestrained, bexamethonium was administered intravenously to block sympathetic nervous system transmission. Prior to bexamethonlum, the mean arterial pressure of young SHR and WKY averaged 123 ± 5 and 109 ± 4 nun Hg respectively (p< 0.05), while adult SHR and WKY averaged 159 ± 7 and 128 ± 3 mm Hg respectively (p< 0.05). Hexamethonium produced an equivalent fall in arterial pressure of young SHR (-32%) and WKY (-30%) and adult SHR (-39%) and WKY (-41%). Vascular resistance was reduced by hexamethonium in the kidney, gut, and hindquarters, but the percent changes were not significant between SHR and WKY. These data suggest that, in both young and adult SHR, vascular resistance and arterial pressure are sustained at elevated levels by some other mechanism than aeurally-derived vasoconstrictor tone.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY The purposes of this study were to determine whether 1) cerebral vessels undergo hypertrophy during chronic hypertension and 2) sympathetic nenes contribute to cerebral vascular changes In chronic hypertension. Morphometiic studies were undertaken in stroke-prone spontaneously hypertensive rats (SP-SHR) and normotenslve Wistar-Kyoto (WKY) rats. Unilateral superior cerrical gangUonectomy was performed in the SP-SHR at 8 weeks of age. When the rats were approximately 13 months old, they were killed and the brain was fixed with formalin at a perfusion pressure of 80% of the rat's systolic pressure. Wall/lumen ratio was measured in approximately 1200 arteries and arterioles. In parenchymal, but not pial, cerebral vessels there was pronounced vascular hypertrophy in SP-SHR: wall/lumen ratio was 0.08 in WKY and 0.14 in SP-SHR (p< 0.05). Sympathetic denervation attenuated the development of vascular hypertrophy in SP-SHR: wall/lumen ratio was 0.14 in the innervated parenchymal vessels, and 0.10 in denervated vessels (p< 0.05). We conclude that cerebral vessels undergo hypertrophy in stroke-prone SHR and speculate that vascular hypertrophy may protect cerebral vessels by reducing wall stress in chronic hypertension. Sympathetic nerves appear to exert a trophic effect on cerebral vascular muscle in chronic hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY To further characterize the role of rasopressin in DOC-salt hypertension, four groups of unilaterally nephrectomized rats were studied: control rats giren no further treatment, rats treated with DOC and giren 1% saline to drink, or rats treated with only DOC, or 1% saline. Only rats treated with DOC or DOC- salt became hypertensive. Control rats and rats treated with only DOC or 1% saline had similar pressor responses to exogenous rasopressin and angiotensin II. Within the DOC-salt group, two populations of rats were identified: one with normal pressor responsiveness to rasopressin, and one with markedly enhanced pressor responsireness to rasopressin. Incidence of enhanced responsiveness increased with duration of treatment. Urinary excretion of rasopressin was elerated in the 1% saline and DOC-salt groups after 1 week of treatment, and in the DOC group after 4 weeks. Howerer, the plasma rasopressin concentration was elerated only in the rats treated with both DOC and saline. It is suggested that rasopressin is essential for the expansion of blood rolume in the early stages of DOC-salt hypertension, and functions as a direct pressor agent only in the later stages.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY The presence of a renln-angiotensin system in the central nervous system (CNS) has been demonstrated by several investigators, but little is known regarding the origin of its components. In this study we have compared the immunological and physical-chemical nature of angiotensinogen in plasma and cerebrospinal fluid (CSF) of human subjects and explored whether differences are present in CSF angiotensinogen concentrations of normal and hypertensive subjects. No significant differences in the nature of plasma and CSF angiotensinogen was observed with respect to molecular weight (65-70,000) electrophoretic mobility (Rfaib − 0.67 ± 0.003) or angiotensin I (AI) generated (pi = 6.6). Following isoelectric focusing, the plasma angiotensinogen was shown to consist of a single component with an isoionic point of 4.40 ± 0.04. CSF angiotensinogen, on the other hand, resolved into three components (pi = 4.76 ± 0.02; 5.16 ± 0.04; 5.76 ± 0.04). Although no correlations were observed between angiotensinogen levels in the CSF or plasma with blood pressure (BP), a statistically significant difference in angiotensinogen concentration of both plasma and CSF was observed between normotensive and hypertensive subjects. The differences in the chemical and immunological nature of human plasma and CSF angiotensinogens suggest that the angiotensinogen of CSF is not of peripheral origin.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID

摘要:

SUMMARY The effects of dietary sodium on the central actions of angiotensin II (All) and on "I-AII binding to brain membranes were investigated in rats fed a low-sodium or control diet and Implanted with a permanent cannula into the lateral cerebral ventrtde. Blood pressure (BP) responses to All injections intracerebroventricularly (I.v.t.) were blunted in sodium-deficient rats compared with controls. The BP increases in response to i.v.t.-injected Carbacbol were the same in the two groups. In sodium-depleted rats, water intake was lower than in controls after All given i.v.t.; higher after 1.5% NtCl i.v.t; and unchanged after Carbachol i.r.t. Tbe pressor response to AQ given I.v.t. was higher hi spontaneously hypertensive rats (SHR) than Wistar- Kyoto (WKY) control rats. This hyperresponsiveness to central All was abolished by feeding a low-sodium diet. Specific1UI-AII binding in vitro to brain membranes was consistently lower hi sodium-depleted rats. The results suggest that sodium depletion modifies the central actions of AH. This may be related in part to changes in the binding properties of All receptors in the brain.

ISSN:0194-911X    

出版商:OVID    

年代:1980

数据来源: OVID