Ontogeny of Corticotropin-Releasing Factor and Arginine Vasopressein in the Rat

Rundle, Susan E.; Funder, John W.

doi:10.1159/000124941

Cited by 43 publications

(19 citation statements)

References 20 publications

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“…ACTH secretion is mainly activated by hypothalamic secretagogues; of these CRH and arginine-vasopressin are the most potent [20]. Both neuropeptides are present at very low levels during the SHRP [2,21]. Removal of the mother may elicit an increase in synthesis, transport and/or secretion of these peptides.…”

Section: Discussionmentioning

confidence: 99%

Effects of Maternal Deprivation on the ACTH Stress Response in the Infant Rat

et al. 1993

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Prolonged maternal deprivation during early ontogeny results in increased basal and stress-induced corticosterone levels. In the following experiments we examined whether these increases were due, at least in part, to augmented ACTH secretion. Thus, ACTH levels were measured in 24-hour maternally deprived and nondeprived 6-, 9-, and 12-day-old pups exposed to a mild stressor (i.e. saline injection followed by placement in a novel environment at room temperature). The results showed: (1) nondeprived pups showed a small response to saline – the response of deprived pups, however, was greater than that of nondeprived pups; (2) the magnitude of the response increased with age; (3) ACTH levels remained elevated for at least 30 min. Subsequent experiments examined whether the continuous exposure to novelty and/or loss of body heat could explain the persistence of this response. Neither variable affected the ACTH response to saline. Our results indicate that factors of maternal origin are partly responsible for the regulation of the ACTH response to stress. Furthermore, the persistence of the response suggests that the negative feedback system in the infant is immature.

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Section: Discussionmentioning

confidence: 99%

Effects of Maternal Deprivation on the ACTH Stress Response in the Infant Rat

et al. 1993

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“…There is a clear developmental influence on its secretion in response to hypotension during fetal life in the sheep (1). Also, AVP is present very early in fetal life (10,11) and appears important in the stimulation of ACTH secretion. Its relationship to the appearance of corticotrophin-releasing factor and its function in the stimulation of ACTH secretion change with development in both the sheep (10) and the rat (11).…”

Section: Discussionmentioning

confidence: 99%

“…Also, AVP is present very early in fetal life (10,11) and appears important in the stimulation of ACTH secretion. Its relationship to the appearance of corticotrophin-releasing factor and its function in the stimulation of ACTH secretion change with development in both the sheep (10) and the rat (11). Thus, we speculate that the inhibitory effects reported here are developmentally based.…”

Section: Discussionmentioning

confidence: 99%

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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“…Naturally, line differ ences in translation efficiency and pituitary responsiveness to CRH [9,14] may occur. Differential developmental pat terns of other ACTH secretagogues, such as vasopressin [8,12,18], also cannot be excluded. Alternatively, increased ACTH may result from a diminished corticosterone feed back signal.…”

Section: Ny Rots Et Al/ Developmental Bruiti Research 92 (1996) ì6mentioning

confidence: 99%

Development of divergence in dopamine responsiveness in genetically selected rat lines is preceded by changes in pituitary-adrenal activity

Rots

Workel²,

Oitzl³

et al. 1996

Developmental Brain Research

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A b s tra c tTwo pharmacogenetically selected Wistar rat lines have been used as a model for individual variability in behavioral and neuroendocrine responses. As a selection criterion the behavioral responsiveness For the dopamine agonist apomorphine was used, giving rise to the apomorphine-susceptible (apo-sus) and apomorphine-unsuseeptible (apo-unsus) rat lines. This selection has been maintained over 16 generations. Recent studies have shown that adult rats of these selection lines also show pronounced differences in responsiveness of the hypothalamic-pituitary-adrenal (HPA) system. In this study we analyzed to what extent the divergence in dopamine phenotype and HPA responsiveness, as observed in adult rats, are linked to possible differences, within both systems, during early postnatal development. Therefore, we measured in neonatal female rats of 10 and 18 days of age several parameters of the dopamine and UFA system which show significant differences in adult rats. These include tyrosine hydroxylase (TH) and dopamine D1 and D2 receptor mRNA levels, which were determined within the nigrostriatal system since this system shows the most pronounced differences hot ween adult rats oF both selection lines. As indices of HPA activity we measured CRH mRNA, ACTH and total and free corticosterone plasma concentrations under basal conditions in the morning. Transcripts of the two types of corticosteroid receptors, mineralocorticoid (MR) and glucocorticoid (GR) receptor were measured in hippocampus and paraventricular nucleus. In 10-day-old rats all dopamine and MPA parameters were similar in rats of the two selection lines, except for GR mRNA in the parvocellular neurons of the paraventricular nucleus of the hypothalamus (PVN) of apo-sus rats, which was significantly higher than in apo-unsus rats. Highteeu-day-old apo-sus rats, however, showed significantly higher ACTH, comparable total corticosterone and a trend towards lower Free corticosterone plasma levels. This HPA profile resembles the situation in adult apo-sus rats as compared with adult apo-unsus rats. Hippocampal GR mRNA expression and thymus weight were also higher in apo-sus rats. In addition, these rats showed an age-related increase in hippocampal MR mRNA expression, while in apo-unsus rats M R mRNA levels did not change between pnd 10 and 18. The measures of the nigrostriatal dopfimme system at day 18 were still similar in rats oF both lines. In conclusion, divergence in the dopamine systems of the two pliarmaeogenetieally selected rat lines emerges subsequent to divergence in pituitary-adrenal activity.

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Ontogeny of Corticotropin-Releasing Factor and Arginine Vasopressein in the Rat

Cited by 43 publications

References 20 publications

Effects of Maternal Deprivation on the ACTH Stress Response in the Infant Rat

Effects of Maternal Deprivation on the ACTH Stress Response in the Infant Rat

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

Development of divergence in dopamine responsiveness in genetically selected rat lines is preceded by changes in pituitary-adrenal activity

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