The Role of Centralα1- andα2-Adrenoceptors in the Regulation of Vasopressin Release and the Cardiovascular System*

Kimura, Tokihisa; Miyake, Shoji; Iitake, Kazuhiro; Ota, Kozo; Matsui, Kuniaki; Yoshinaga, Kaoru

doi:10.1210/endo-114-4-1426

Cited by 59 publications

(19 citation statements)

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“…Numerous experiments in a variety of animal models have ascribed both stimulatory and inhibitory roles to the a-1 and a-2 adrenoceptors located on the AVP secreting neurons of the hypothalamus (3,5,6,(12)(13)(14). It is possible that the differences between these studies and ours could be from the basis of interspecies variation as well as from a difference in the developmental stage of the subjects.…”

Section: Discussionmentioning

confidence: 80%

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Central α-1-Adrenergic Control of Vasopressin Secretion in Newborn Lambs

1991

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ABSTRACT. The hypothesis that central a-1 adrenoceptors are inhibitory to the hypotension-induced secretion of vasopressin was tested by subjecting lambs that were instrumented for a long term to varying degrees of hypotension after intracerebroventricular injections of prazosin or placebo. Eight lambs in the 1st wk of life treated with intracerebroventricular injections of placebo had their mean arterial blood pressures decreased 14 and 21% by i.v. infusion of nitroprusside. Arginine vasopressin levels rose to 7.3 1 2.4 pmol/L only with the greater degree of hypotension. When the lambs were treated with intracerebroventricular injections of 1 pg/kg of prazosin, the blood pressures were decreased 13 and 23%, and the vasopressin levels were 15.4 2 16.6 and 27.5 2 20.3 pmol/L, respectively. A relationship was shown between the degree of hypotension and the plasma arginine vasopressin levels with both the placebo and prazosin, the slope being much steeper for the prazosin treatment (-1.11) than for the placebo treatment (-0.31). Plasma renin activity was increased a similar amount in both groups, and there was no change in plasma cortisol levels. We conclude that a-1 adrenoceptors in the brain are inhibitory to the secretion of arginine vasopressin. These results differ from observationsh adult rats and dogs and may be accounted for by developmental or species differences. (Pediatr Res 30: 50-54,1991) Abbreviations AVP, arginine vasopressin CSF, cerebrospinal fluid HR, heart rate ICV, intracerebroventricular MABP, mean arterial blood pressure PE, phenylephrine PRA, plasma renin activity AVP has been shown to have a role in fetal and neonatal cardiovascular homeostasis as a "stress" hormone (1-3). Neonatal and fetal AVP secretion may be induced by hypoxia, hypotension, and acidosis. Levels of this hormone are particularly high around the time of delivery, especially in the case of fetal asphyxia (3).Although there is an increasing body of knowledge concerning the control of AVP secretion in adult animals, little is known about the neonate. CNS a-1 and a-2 adrenoceptors are involved in the regulation of AVP secretion in adult animals (4-6). We have previously reported that lamb fetuses treated with i.v. prazosin, an a-1 adrenoceptor blocker, and subsequently subjected to hypotensive hemorrhage had excessive levels of AVP when compared with similar hemorrhagic hypotension without prazosin (7). This observation led us to hypothesize that hypothalamic a-1 receptors exert an inhibitory influence on the secretion of AVP in response to hypotension in the near-term lamb fetus. In the neonatal lamb, AVP levels after hemorrhage were similar with prazosin and with vehicle, but the relative decrease in blood pressure was less in the prazosin-treated lambs and may have been subthreshold for the secretion of AVP (2). To prove our hypothesis, we designed an experiment in which CNS a-1 adrenoceptor blockade was achieved in the newborn lamb by ICV injection, rather than i.v. injection of prazosin. In so doing, we hoped to avoid t...

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Section: Discussionmentioning

confidence: 80%

“…In addition to the a-1 adrenergic system, other receptors have been shown to be involved (5,6). The rapid changes occurring in AVP-related mechanisms in the nearterm fetus raise important questions about the development of this system.…”

Section: Discussionmentioning

confidence: 99%

Central α-1-Adrenergic Control of Vasopressin Secretion in Newborn Lambs

1991

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“…These results suggest that the hypotensive and bradycardic actions of L-dopa are mediated by stimulation of central a 2 -adrenergic receptors, and again, this conclusion is consistent with previous reports. 6 -21 " 23 The decreases in blood pressure and heart rate produced by L-dopa are thought to result from a reduction in sympathetic neural activity and an increase in cardiac vagal activity.…”

Section: Inhibition Of Vasopressin Secretion By L-dopa/fo/rf Et Almentioning

confidence: 99%

“…5 " 9 Although there is general agreement that central catecholamines are involved in the control of vasopressin release, there is still controversy concerning the nature of this control. Many investigators have concluded that brain catecholamines act to inhibit vasopressin release, 6 ' '• 10~15 while others have presented evidence for a stimulatory effect. 8 ' l6~18 In addition, the relative importance of dopamine and norepinephrine is not clear.…”

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confidence: 99%

Role of dopamine in the inhibition of vasopressin secretion by L-dopa in carbidopa-treated dogs.

Reid¹,

Chou²,

Chang³

et al. 1986

Hypertension

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SUMMARY Elevation of brain catecholamine levels by systemic administration of L-dopa in dogs pretreated with the dopa decarboxylase inhibitor carbidopa inhibits the secretion of vasopressin and adrenocorticotropic hormone (ACTH) and decreases arterial blood pressure. The aim of the present study was to determine 1) whether the inhibition of vasopressin secretion is mediated by dopamine or norepinephrine, both of which have been implicated in the control of vasopressin secretion, and 2) whether the decrease in vasopressin secretion contributes to the suppression of ACTH secretion and fall in blood pressure produced by L-dopa. This was accomplished by comparing the effects of dopamine and a-adrenergic receptor antagonists on vasopressin, ACTH, and blood pressure responses to L-dopa. The effect of a specific antagonist of the vasoconstrictor action of vasopressin also was studied. Injection of L-dopa (20 mg/kg i.v.) in dogs pretreated with carbidopa (20 mg/kg i.v.) caused reductions in plasma vasopressin concentration (from 16.0 ± 4.8 to 3.8 ± 0.9 pg/ml; p<0.05), plasma ACTH concentration (from 96.0 ± 20.4 to 49.2 ± 10.0 pg/ml; p<0.05), and mean arterial pressure (from 121 ± 6 to 78 ± 5 mm Hg; p<0.05). Pretreatment with pimozide (1 mg/kg i.p.) completely blocked the inhibition of vasopressin secretion by L-dopa but failed to block the suppression of ACTH secretion (57.6 ± 11.8 to 34.0 ± 5.1 pg/ml; p<0.05) or the decrease in mean arterial pressure (126 ± 5 to 93 ± 7 mm Hg; p<0.05). The antihypertensive effect of L-dopa was reduced by prazosin (97 ± 3 to 82 ± 6 mm Hg; p<0.05) and blocked by yohimbine, but neither drug blocked the suppression of plasma vasopressin or ACTH. Administration of a vasopressin antagonist did not decrease arterial pressure and caused only a small, delayed reduction in plasma ACTH concentration. These studies provide evidence that the inhibition of vasopressin secretion by L-dopa is mediated by dopamine rather than by norepinephrine. The failure of a vasopressin antagonist to significantly decrease blood pressure or ACTH secretion and the dissociation of the effects of L-dopa on vasopressin release, blood pressure, and ACTH secretion argue against a major role for vasopressin in the blood pressure and ACTH responses to L-dopa. Received December 13, 1985; accepted April 15, 1986. variety of stimuli. 3 4 In addition, the release of vasopressin can be altered by central administration of catecholamines, other adrenergic agonists, and adrenergic blocking drugs.5 " 9 Although there is general agreement that central catecholamines are involved in the control of vasopressin release, there is still controversy concerning the nature of this control. Many investigators have concluded that brain catecholamines act to inhibit vasopressin release, 6 ' '• 10~15 while others have presented evidence for a stimulatory effect. 8 ' l6~18 In addition, the relative importance of dopamine and norepinephrine is not clear.In a previous investigation in this laboratory, we reported that intravenous administratio...

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“…NE can increase the central and peripheral release of neuropeptides mainly via the involvement of HA-ergic neurons [67]. Nevertheless, NE has also been reported to inhibit AVP release [71][72][73]. Correlative roles of AVP and 5-HT [31] and/or NE [56] in various aspects of emotional or social behavior or the related disorders have likewise been described.…”

Section: Discussionmentioning

confidence: 99%

Study of neurogenic involvement in arginine-vasopressin and oxytocin release under basal and environmentally stimulated conditions

Nagyéri¹

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The Role of Centralα₁- andα₂-Adrenoceptors in the Regulation of Vasopressin Release and the Cardiovascular System^*

Cited by 59 publications

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Central α-1-Adrenergic Control of Vasopressin Secretion in Newborn Lambs

Central α-1-Adrenergic Control of Vasopressin Secretion in Newborn Lambs

Role of dopamine in the inhibition of vasopressin secretion by L-dopa in carbidopa-treated dogs.

Study of neurogenic involvement in arginine-vasopressin and oxytocin release under basal and environmentally stimulated conditions

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