Studies on the role of TRH and corticosterone in the regulation of prolactin and thyrotrophin secretion during lactation

1996 ◽  
Vol 148 (2) ◽  
pp. 325-336 ◽  
Author(s):  
G A C van Haasteren ◽  
H van Toor ◽  
W Klootwijk ◽  
B Handler ◽  
E Linkels ◽  
...  
Keyword(s):  
Litter Size ◽  
Median Eminence ◽  
Plasma Corticosterone ◽  
Adrenal Weight ◽  
Negative Effects ◽  
Mrna Content ◽  
Basal Plasma ◽  
Thyroid Axis ◽  
Acute Changes ◽  
Plasma Prl

Abstract This study describes the effects of litter size and acute suckling on the synthesis and release of hypothalamic TRH, as indirectly estimated by determination of hypothalamic prothyrotrophin-releasing hormone (proTRH) mRNA and median eminence TRH content. The effects of litter size (five or ten pups) were studied throughout lactation, while suckling-induced acute changes were analyzed on day 13 of lactation in dams with ten pups. In view of the enhanced adrenal activity during lactation and recent evidence that corticosteroids have negative effects on hypothalamic TRH, we also studied adrenalectomized (ADX) dams treated with corticosterone to maintain basal plasma corticosterone levels. In addition to an increased plasma level of prolactin (PRL), adrenal weight and plasma corticosterone increased, while plasma TSH, tri-iodothyronine (T3), thyroxine (T4) and free T4 (FT4) levels decreased during lactation. Litter size correlated positively with plasma PRL, adrenal weight and plasma corticosterone. No effect of litter size was observed on plasma T3, but rats with ten pups had lower plasma TSH, T4 and FT4 than rats with a five-pup litter. Compared with dioestrous rats, lactating rats showed an increased hypothalamic proTRH mRNA content on day 2, but not on days 8 and 15 of lactation. Median eminence TRH in lactating rats gradually increased until day 15 and decreased thereafter. Acute suckling, after a 6-h separation of mother and pups, rapidly increased plasma PRL and corticosterone in the mothers, but had no effects on plasma TSH and thyroid hormone levels. Hypothalamic proTRH mRNA increased twofold after 0·5 h of suckling, and then gradually returned to presuckling values after 6 h. Compared with sham-operated rats, corticosterone-substituted ADX rats with ten pups had increased plasma PRL and TSH, hypothalamic proTRH mRNA and pituitary TSH β mRNA on day 15 of lactation. Moreover, while acute suckling did not enhance TSH release in sham-operated rats, it provoked not only PRL but also TSH release in corticosterone-substituted ADX dams. It is concluded that suckling exerts a rapid, positive effect on hypothalamic proTRH mRNA content. However, the concurrent enhanced adrenal activity has negative effects on hypothalamic proTRH gene expression resulting in a suppressed hypophysial-thyroid axis during lactation. While TRH appears to play a role in PRL release during the first days of lactation and during acute suckling, TRH seems not important in maintaining PRL secretion during continued suckling. Journal of Endocrinology (1996) 148, 325–336

Basal and evoked levels of bioassayable growth hormone are altered by hindlimb unloading

2006 ◽  
Vol 100 (3) ◽  
pp. 1037-1042 ◽  
Author(s):  
A. J. Bigbee ◽  
R. E. Grindeland ◽  
R. R. Roy ◽  
H. Zhong ◽  
K. L. Gosselink ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Fiber Type ◽  
Plasma Corticosterone ◽  
Hindlimb Unloading ◽  
Male Rats ◽  
Afferent Fibers ◽  
Basal Plasma ◽  
Proprioceptive Afferents ◽  
Acute Changes

Bioassayable growth hormone (BGH) in rats is released in large quantities from the pituitary in response to the activation of large, proprioceptive afferent fibers from fast and mixed fiber-type hindlimb musculature. We hypothesized that hindlimb unloading (HU) of adult male rats would 1) reduce the basal levels of plasma BGH, and 2) abolish stimulus-induced BGH release. Rats were exposed to HU for 1, 4, or 8 wk. Plasma and pituitaries were collected under isoflurane anesthesia for hormone analyses. Additionally, at 4 and 8 wk, a subset of rats underwent an in situ electrical stimulation (Stim) of tibial nerve proprioceptive afferents. Basal plasma BGH levels were significantly reduced (−51 and −23%) after 1 and 8 wk of HU compared with ambulatory controls (Amb). Although Amb-Stim rats exhibited increased plasma BGH levels (88 and 143%) and decreased pituitary BGH levels (−27 and −22%) at 4 and 8 wk, respectively, stimulation in HU rats had the opposite effect, reducing plasma BGH (−25 and −33%) and increasing pituitary BGH levels (47 and 10%) relative to HU alone at 4 and 8 wk. The 22-kDa form of GH measured by immunoassay and the plasma corticosterone, T3, T4, and testosterone levels were unchanged by HU or Stim at all time points. These data suggest that BGH synthesis and release from the pituitary are sensitive both to chronically reduced neuromuscular loading and to acute changes in neuromuscular activation, independent of changes in other circulating hormones. Thus BGH may play a role in muscle, bone, and metabolic adaptations that occur in response to chronically unloaded states.

Effects of paraventricular lesions on stimulated ACTH release and CRF in stalk-median eminence of the rat

1981 ◽  
Vol 240 (4) ◽  
pp. E441-E446 ◽  
Author(s):  
G. B. Makara ◽  
E. Stark ◽  
M. Karteszi ◽  
M. Palkovits ◽  
G. Rappay
Keyword(s):  
Median Eminence ◽  
Corticosterone Level ◽  
Plasma Corticosterone ◽  
Surgical Trauma ◽  
Acth Level ◽  
Plasma Acth ◽  
Medial Basal Hypothalamus ◽  
Plasma Acth Level ◽  
Basal Plasma ◽  
Corticosterone Response

The effects of destroying the paraventricular nucleus (PVN) of the rat hypothalamus on pituitary-adrenal function were studied. Four days after PVN lesions were placed with a rotating knife, the basal plasma corticosterone level was normal, but the corticosterone response to electrical stimulation of the medial basal hypothalamus, surgical trauma, and ether-venesection stress was significantly inhibited. Four and 8 days after PVN lesioning and adrenalectomy, the basal plasma ACTH level was lower, and the rise of plasma ACTH level elicited by a 3-min ether inhalation was significantly smaller than in the adrenalectomized controls. Corticotropin-releasing factor (CRF) activity in the stalk-median eminence extracts from PVN-lesioned rats was significantly less than in the control extracts. The weight of the adrenals was decreased by both 2 and 4 wk after PVN destruction, and 2 wk after hemiadrenalectomy, the compensatory adrenal hypertrophy was inhibited. The plasma corticosterone response to ether-venesection stress was inhibited only temporarily because it returned to normal by the end of the 4th postoperative week. The results are consistent with the hypothesis that a substantial portion of CRF-containing fibers in the stalk-median eminence region either originate from or run though the PVN or its immediate vicinity.

Starvation-induced changes in the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA and the hypothalamic release of proTRH-derived peptides: role of the adrenal gland

1995 ◽  
Vol 145 (1) ◽  
pp. 143-153 ◽  
Author(s):  
G A C van Haasteren ◽  
E Linkels ◽  
W Klootwijk ◽  
H van Toor ◽  
J M M Rondeel ◽  
...  
Keyword(s):  
Thyroid Hormones ◽  
Thyroid Function ◽  
Food Deprivation ◽  
Median Eminence ◽  
Plasma Corticosterone ◽  
Portal Blood ◽  
Negative Effects ◽  
Releasing Hormone ◽  
Hypophysial Portal ◽  
Adrenalectomized Rats

Abstract The purpose of this study was to investigate the mechanisms involved in the reduced thyroid function in starved, young female rats. Food deprivation for 3 days reduced the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA, the amount of proTRH-derived peptides (TRH and proTRH160–169) in the paraventricular nucleus, the release of proTRH-derived peptides into hypophysial portal blood and the pituitary levels of TSHβ mRNA. Plasma TSH was either not affected or slightly reduced by starvation, but food deprivation induced marked increases in plasma corticosterone and decreases in plasma thyroid hormones. Refeeding after starvation normalized these parameters. Since the molar ratio of TRH and proTRH160–169 in hypophysial portal blood was not affected by food deprivation, it seems unlikely that proTRH processing is altered by starvation. The median eminence content of pGlu-His-Pro-Gly (TRH-Gly, a presumed immediate precursor of TRH), proTRH160–169 or TRH were not affected by food deprivation. Since median eminence TRH-Gly levels were very low compared with other proTRH-derived peptides it is unlikely that α-amidation is a rate-limiting step in hypothalamic TRH synthesis. Possible negative effects of the increased corticosterone levels during starvation on proTRH and TSH synthesis were studied in adrenalectomized rats which were treated with corticosterone in their drinking water (0·2 mg/ml). In this way, the starvation-induced increase in plasma corticosterone could be prevented. Although plasma levels of thyroid hormones remained reduced, food deprivation no longer had negative effects on hypothalamic proTRH mRNA, pituitary TSHβ mRNA and plasma TSH in starved adrenalectomized rats. Thus, high levels of corticosteroids seem to exert negative effects on the synthesis and release of proTRH and TSH. This conclusion is corroborated by the observation that TRH release into hypophysial portal blood became reduced after administration of the synthetic glucocorticosteroid dexamethasone. On the basis of these results, it is suggested that the reduced thyroid function during starvation is due to a reduced synthesis and release of TRH and TSH. Furthermore, the reduced TRH and TSH synthesis during food deprivation are probably caused by the starvation-induced enhanced adrenal secretion of corticosterone. Journal of Endocrinology (1995) 145, 143–153

Possible role of corticosterone in the down-regulation of the hypothalamo-hypophysial-thyroid axis in streptozotocin-induced diabetes mellitus in rats

1997 ◽  
Vol 153 (2) ◽  
pp. 259-267 ◽  
Author(s):  
G A C van Haasteren ◽  
E Sleddens-Linkels ◽  
H van Toor ◽  
W Klootwijk ◽  
F H de Jong ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Median Eminence ◽  
Plasma Corticosterone ◽  
Diabetic Rats ◽  
Type I ◽  
Thyroid Axis ◽  
Streptozotocin Induced Diabetes ◽  
The Difference

Abstract We investigated the effects of diabetes mellitus on the hypothalamo-hypophysial-thyroid axis in male (R×U) F1 and R-Amsterdam rats, which were found to respond to streptozotocin (STZ)-induced diabetes mellitus with no or marked increases, respectively, in plasma corticosterone. Males received STZ (65 mg/kg i.v.) or vehicle, and were killed 1, 2 or 3 weeks later. At all times studied, STZ-induced diabetes mellitus resulted in reduced plasma TSH, thyroxine (T4) and 3,5,3′-tri-iodothyronine (T3). Since the dialyzable T4 fraction increased after STZ, probably as a result of decreased T4-binding prealbumin, plasma free T4 was not altered during diabetes. In contrast, both free T3 and its dialyzable fraction decreased during diabetes, which was associated with an increase in T4-binding globulin. Hepatic activity of type I deiodinase decreased and T4 UDP-glucuronyltransferase increased after STZ treatment. Thus, the lowered plasma T3 during diabetes may be due to decreased hepatic T4 to T3 conversion. Median eminence content of TRH increased after STZ, suggesting that hypothalamic TRH release is reduced during diabetes and that this is not caused by impaired synthesis or axonal transport of TRH to the median eminence. Hypothalamic proTRH mRNA did not change in diabetic (R×U) F1 rats during the period of observation, but was lower in R-Amsterdam rats 3 weeks after STZ. Similarly, pituitary TSH and TSHβ mRNA had decreased in R-Amsterdam rats by 1 week after STZ treatment, but did not change in (R×U) F1 rats. The difference between the responses in diabetic R-Amsterdam and (R×U) F1 rats may be explained on the basis of plasma corticosterone levels which increased in R-Amsterdam rats only. Hypothalamic TRH content was not affected by diabetes mellitus, but the hypothalami of diabetic rats released less TRH in vitro than those of control rats. Moreover, insulin had a positive effect on TRH release in vitro. In conclusion, the reduced hypothalamic TRH release during diabetes is probably not caused by decreases in TRH synthesis or transport to the median eminence, but seems to be due to impaired TRH release from the median eminence which may be related to the lack of insulin. Inhibition of proTRH and TSHβ gene expression in diabetic R-Amsterdam rats is not a primary event but appears to be secondary to enhanced adrenal activity in these animals during diabetes. Journal of Endocrinology (1997) 153, 259–267

scholarly journals A Novel Mouse Model for Acute and Long-Lasting Consequences of Early Life Stress

Endocrinology ◽  
2008 ◽  
Vol 149 (10) ◽  
pp. 4892-4900 ◽  
Author(s):  
Courtney J. Rice ◽  
Curt A. Sandman ◽  
Mohammed R. Lenjavi ◽  
Tallie Z. Baram
Keyword(s):  
Mouse Model ◽  
Paraventricular Nucleus ◽  
Life Stress ◽  
Early Life ◽  
Molecular Mechanisms ◽  
Early Life Stress ◽  
Plasma Corticosterone ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Basal Plasma

Chronic early-life stress (ES) exerts profound acute and long-lasting effects on the hypothalamic-pituitary-adrenal system, with relevance to cognitive function and affective disorders. Our ability to determine the molecular mechanisms underlying these effects should benefit greatly from appropriate mouse models because these would enable use of powerful transgenic methods. Therefore, we have characterized a mouse model of chronic ES, which was provoked in mouse pups by abnormal, fragmented interactions with the dam. Dam-pup interaction was disrupted by limiting the nesting and bedding material in the cages, a manipulation that affected this parameter in a dose-dependent manner. At the end of their week-long rearing in the limited-nesting cages, mouse pups were stressed, as apparent from elevated basal plasma corticosterone levels. In addition, steady-state mRNA levels of CRH in the hypothalamic paraventricular nucleus of ES-experiencing pups were reduced, without significant change in mRNA levels of arginine vasopressin. Rearing mouse pups in this stress-provoking cage environment resulted in enduring effects: basal plasma corticosterone levels were still increased, and CRH mRNA levels in paraventricular nucleus remained reduced in adult ES mice, compared with those of controls. In addition, hippocampus-dependent learning and memory functions were impaired in 4- to 8-month-old ES mice. In summary, this novel, robust model of chronic early life stress in the mouse results in acute and enduring neuroendocrine and cognitive abnormalities. This model should facilitate the examination of the specific genes and molecules involved in the generation of this stress as well as in its consequences.

The influence of vanadate on insulin counter-regulatory hormones in obese fa/fa rats

1991 ◽  
Vol 131 (2) ◽  
pp. 185-191 ◽  
Author(s):  
S. M. Brichard ◽  
L. N. Ongemba ◽  
J. Kolanowski ◽  
J. C. Henquin
Keyword(s):  
Body Weight ◽  
Food Restriction ◽  
Body Weight Gain ◽  
Plasma Corticosterone ◽  
Plasma Glucagon ◽  
Lower Plasma ◽  
Peripheral Tissues ◽  
Insulin Resistant ◽  
Glucose Homoeostasis ◽  
Basal Plasma

ABSTRACT Vanadate has been shown to improve glucose homoeostasis in mildly glucose-intolerant and severely insulin-resistant fa/fa rats. The present study examined whether changes in insulin counter-regulatory hormones contribute to this beneficial effect of vanadate. Since oral administration of Na3VO4 caused a decrease in food intake and stopped the increase in body weight, vanadate-treated fa/fa rats were compared with both controls with food available ad libitum and pair-fed rats. Slightly lower plasma glucose levels were maintained in conjunction with markedly lower plasma insulin levels in vanadatetreated rats, and this effect was not simply due to the smaller body weight of the animals. Compared with control rats, treatment with vanadate affected neither basal plasma glucagon levels nor the increase in glucagon levels observed after insulin-induced hypoglycaemia or after i.v. injection of arginine. Compared with pair-fed rats, treatment with vanadate prevented the fall in basal plasma glucagon and its exaggerated rise in response to insulin that mere food restriction produced. Plasma corticosterone levels were high in fa/fa rats. Vanadate and pair-feeding similarly decreased basal plasma levels of corticosterone as well as nocturnal corticosteronuria. Thus the attenuation of the hypercorticism of fa/fa rats results from the reduction in body weight gain rather than from a specific action of vanadate. Vanadate did not influence urinary excretion of noradrenaline, an index of neural sympathetic activity, but prevented the increase in adrenaline excretion, an index of adrenal medulla activity, that was produced by food restriction in pair-fed rats. In conclusion, vanadate administration has no or little specific effects on three major insulin counter-regulatory hormones. This reinforces the suggestion that the beneficial effects of vanadate on glucose homoeostasis in fa/fa rats are mainly due to a correction of insulin resistance in peripheral tissues. Journal of Endocrinology (1991) 131, 185–191

Sensitizing effect of treatment with estrogens on TSH response to TRH in male rats.

1977 ◽  
Vol 233 (3) ◽  
pp. E235 ◽  
Author(s):  
A De Lean ◽  
F Labrie
Keyword(s):  
Estradiol Benzoate ◽  
Thyroid Stimulating Hormone ◽  
Prolactin Secretion ◽  
Male Rats ◽  
Intact Male ◽  
Basal Plasma ◽  
Prolactin Content ◽  
High Doses ◽  
Sensitizing Effect ◽  
Plasma Prl

Daily administration of estradiol benzoate (10 microgram/100 g body wt) to intact male rats led to a twofold increase of the plasma TSH (thyroid-stimulating hormone) response to thyrotropin-releasing hormone (TRH) after 4 and 7 days of treatment whereas the basal plasma TSH level was not affected. The basal plasma PRL concentration and the PRL response to TRH were both markedly increased by estrogen treatment. The TSH pituitary content remained unchanged, whereas the PRL pituitary content increased in parallel with the effect on PRL secretion. Treatment with estrogens for 1 wk sensitized the TSH secretory response to low doses of TRH (10 ng), whereas no significant effect on the response was found at high doses of the neurohormone. The present data show that the stimulatory effect of estrogens on the TSH response to TRH is due to true sensitization of the thyrotrophs to the action of the neurohormone, whereas that on prolactin secretion can result partly from increased pituitary prolactin content.

scholarly journals Extension of Survival in Bilaterally Adrenalectomized Mice by Implantation of SF-1/Ad4BP-Induced Steroidogenic Cells

Endocrinology ◽  
2020 ◽  
Vol 161 (3) ◽  
Author(s):  
Tomoko Tanaka ◽  
Chikao Aoyagi ◽  
Kuniaki Mukai ◽  
Koshiro Nishimoto ◽  
Shohta Kodama ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Corticosterone Level ◽  
Plasma Corticosterone ◽  
Loading Test ◽  
Steroidogenic Factor 1 ◽  
Basal Plasma ◽  
Steroidogenic Cells ◽  
And Control ◽  
Cell Transplantation Therapy ◽  
Transplantation Therapy

Abstract Mesenchymal stroma/stem cells (MSCs) exist in adult tissues, such as adipose tissue and bone marrow, and differentiate into cells of multiple lineages. In previous studies, we found that MSCs differentiate into steroidogenic cells by forced expression of steroidogenic factor 1 (SF-1)/adrenal 4 binding protein (Ad4BP), the master regulator of steroidogenesis and differentiation of pituitary gonadotrophs, adrenal glands, and gonads. In this study, SF-1/Ad4BP-induced steroidogenic cells derived from mouse adipose tissue–derived MSCs (ADSCs) were implanted under the kidney capsule of bilateral adrenalectomized (bAdx) mice. bAdx mice did not survive after 7 days. However, 4 of 9 bAdx mice implanted with SF-1/Ad4BP-induced steroidogenic cells, 1 of 10 bAdx mice transplanted with control ADSCs, and bAdx mice transplanted with an adrenal gland survived for 30 days. Plasma corticosterone levels in bAdx mice implanted with SF-1/Ad4BP-induced steroidogenic cells and control ADSCs were 5.41 ± 2.26 ng/mL (mean ± SEM) and undetectable at 7 days after implantation, respectively. After removal of the kidney bearing the graft from the surviving mice at 30 days after implantation, plasma corticosterone was not detected in any of the samples. Immunohistochemical staining revealed SF-1/Ad4BP-positive cells under the capsule of the kidney. Although we performed an adrenocorticotropin (ACTH) loading test on bAdx mice implanted with SF-1/Ad4BP-induced steroidogenic cells, ACTH responsiveness was not observed. Implantation of steroidogenic cells derived from ADSCs into bAdx mice increased the basal plasma corticosterone level and extended the survival of bAdx mice, suggesting the capability of restoring steroidogenic cells by cell transplantation therapy for adrenal insufficiency.

Enhanced depressor effect of bromocriptine in the DOCA/NaCl hypertensive rat

1985 ◽  
Vol 249 (1) ◽  
pp. H64-H70 ◽  
Author(s):  
S. Nagahama ◽  
Y. F. Chen ◽  
S. Oparil
Keyword(s):  
Adrenal Medulla ◽  
Dopaminergic System ◽  
Plasma Norepinephrine ◽  
Depressor Response ◽  
Hypertensive Rat ◽  
Basal Plasma ◽  
Plasma Prl ◽  
Depressor Effect ◽  
Dose Dependent

To elucidate the role of the dopaminergic system in the maintenance of hypertension in the deoxycorticosterone acetate (DOCA)/NaCl hypertensive rat, the responses of mean arterial pressure (MAP), plasma norepinephrine (NE), epinephrine (E), and prolactin (PRL) to intravenous (iv) administration of bromocriptine, a dopamine agonist, and hexamethonium bromide, a ganglion blocker, were examined in conscious, unrestrained 4-wk DOCA/NaCl hypertensive rats. Bromocriptine was administered to adrenomedullectomized (ADMX) rats to assess the role of the adrenal medulla in its depressor effect. Bromocriptine (50, 250, and 500 micrograms/kg) and hexamethonium (3 and 30 mg/kg) caused dose-dependent decreases in MAP that were greater in DOCA/NaCl rats than in uninephrectomized controls. Basal plasma NE, E, and PRL were significantly higher in DOCA/NaCl rats than in controls. Bromocriptine (500 micrograms/kg iv) decreased plasma PRL to undetectable levels and increased plasma E significantly without changing NE levels in DOCA/NaCl and uninephrectomized control rats. In ADMX rats bromocriptine (500 micrograms/kg iv) decreased MAP, PRL, and NE without affecting E levels. These results suggest that the depressor response to bromocriptine could be related to inhibition of sympathetic outflow without participation of the adrenal medulla. The hyperprolactinemia and enhanced depressor response to bromocriptine observed in DOCA/NaCl animals suggest that the dopaminergic system might be altered in this model of hypertension.

Mechanism of restoration of ACTH release in rats with long-term lesions of the paraventricular nuclei

1986 ◽  
Vol 111 (1) ◽  
pp. 75-82 ◽  
Author(s):  
J. Dohanics ◽  
G. Kapócs ◽  
T. Janáky ◽  
J. Z. Kiss ◽  
G. Rappay ◽  
...  
Keyword(s):  
Median Eminence ◽  
Plasma Concentrations ◽  
Plasma Acth ◽  
Corticotrophin Releasing Factor ◽  
Paraventricular Nuclei ◽  
Basal Plasma ◽  
Corticosterone Response ◽  
Intact Rats ◽  
Acth Release

ABSTRACT The effects of lesions in the paraventricular nucleus (PVN) on the adrenocortical response to ether stress were investigated in neurohypophysectomized and intact rats. During the first 4 days after placement of lesions in the PVN, the corticosterone response to ether stress was almost completely inhibited. It then gradually increased and, within 4–6 weeks of surgery, was restored to about 60% of that in sham-operated rats. Basal plasma concentrations of corticosterone were low in rats after placement of lesions in the PVN and/or after neurointermediate lobectomy (NILX). Corticosterone responses to ether stress were similar in groups submitted to PVN lesions and/or NILX, and lower than those in the appropriate sham-operated groups. In all lesioned groups, plasma ACTH concentrations after a combination of stressors (ether plus laparotomy) were also lower than those in the sham-operated groups. Six weeks after lesioning of the PVN, immunoreactive rat corticotrophin-releasing factor-41 (rCRF-41) concentrations in stalk-median eminence (SME) extract fell to about 5% of that in sham-operated rats, while immunoreactive arginine vasopressin (AVP) concentrations did not change. Immunohistochemistry revealed a substantial decrease in rCRF-41 immunostaining of the median eminence 6 weeks after lesioning of the PVN, though randomly located clusters of stained terminals were still seen in the whole rostro-caudal extent of the median eminence. A mixture containing synthetic rCRF-41 and AVP, in proportions similar to those in SME extracts from sham-operated rats, caused significantly less release of ACTH from anterior pituitary cell cultures than did SME extracts from sham-operated rats. Extracts of SME from PVN-lesioned rats released as much ACTH as a mixture containing synthetic rCRF-41 and AVP in proportions similar to those in the SME extracts from PVN-lesioned rats. Extracts of SME from either PVN-lesioned or sham-operated rats did not cause a significant increase in the amount of ACTH released when preincubated with antisera to both rCRF-41 and AVP. It is suggested that (1) the restoration of the adrenocortical reponse to ether stress, evident within a few days of placement of lesions in the PVN, occurs independently of neurohypophysial function; (2) the full corticosterone and ACTH response to ether or ether plus laparotomy stress requires not only an intact PVN but also an intact neurointermediate lobe; (3) SME extracts from sham-operated rats contain a factor(s) with the ability to potentiate the ACTHreleasing effect of rCRF-41 and AVP; and (4) the ACTH-releasing activity of SME extract obtained from rats with long-term PVN lesions is probably due to its remaininJ content of rCRF-41 and AVP. J. Endocr. (1986) 111, 75–82

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