La separación materna durante la lactancia altera los niveles basales del sistema neuroendocrino en ratas adolescentes y adultas / Maternal separation during nursing alters basal neuroendocrine levels in juvenile and adult rats

Introducción. En diversos modelos animales, incluido el de la separación materna durante la lactancia, se ha demostrado que las experiencias tempranas adversas, como el maltrato, el abandono materno y el estrés psicosocial, pueden favorecer el desarrollo de algunas enfermedades mentales, pero no se han descrito completamente varios de los cambios que se producen en el sistema neuroendocrino. Objetivo. Determinar si la separación materna durante la lactancia modificaba los niveles basales de neurohormonas como la corticosterona, la corticotropina (ACTH), la oxitocina y la vasopresina (ADH), en ratas jóvenes (35 días) y adultas (90 días). Materiales y métodos. Se separaron ratas Wistar de sus madres durante dos periodos de tres horas diarias a lo largo de los 21 días de lactancia. A los 35 y 90 días se tomaron muestras de los grupos de las ratas de control y de las separadas de la madre, para obtener el suero y posteriormente medir cada una de las hormonas mediante un ensayo inmunoenzimático. Resultados. Las concentraciones de corticosterona fueron mayores en las hembras adultas de control que en el resto de los grupos, y menores en los machos adultos de control. Las de ACTH fueron mayores en los machos y hembras jóvenes separadas de la madre que en los grupos de adultos. Los niveles de oxitocina fueron significativamente mayores en las hembras adultas separadas de la madre que en los otros grupos y significativamente menores en los machos adultos. En cuanto a la vasopresina, los grupos separados de la madre tuvieron concentraciones menores, en comparación con los grupos de jóvenes y adultos de control. Conclusiones. Estos resultados muestran que el estrés temprano al que fueron sometidas las ratas, produjo cambios en las respuestas del eje hipotálamo-hipófisis-suprarrenal, las cuales variaron según el sexo y la edad.

Introduction: Work with different animal models including that of maternal separation during nursing has shown that early adverse experiences such as abuse, maternal abandonment and psychosocial stress may favor the development of various psychopathologies. However, several neuroendocrine changes have not been completely described yet. Objective: To establish whether maternal separation during nursing modifies the basal levels of neurohormones such as corticosterone, ACTH, oxytocin and vasopressin in juvenile and adult rats (aged 35 and 90 days, respectively). Materials and methods: Wistar rats were separated from their mothers for two periods of 3 hours per day during the 21 days of nursing. Once these rats had reached 35 and then 90 days of age, blood samples were taken from both the separated and control groups to obtain serum for immunoenzymatic assays and measure the levels of each of the hormones. Results: Concentrations of corticosterone were higher in control adult females in comparison with the rest of the groups and lower in the control adult males. Those of ACTH were higher in the separated young males and females than in the adult groups. Oxytocin levels were significantly higher in the separated adult females in comparison with the other groups and significantly lower in the adult males. With respect to vasopressin, the separated groups had lower concentrations than the young and adult control groups. Conclusions: These results show that the early stress to which rats were submitted produced changes in the basal responses of the hypothalamic-pituitary-adrenal axis, that these responses were distinct in males and females and that they also differed according to age.

MDCK cells express serotonin-regulable 11beta-hydroxysteroiddehydrogenase type 2

Prior to this work, we found that adrenal as well as extra-adrenal factors activate the response of renal 11beta-hydroxysteroid dehydrogenase 2 to stressful situations. These results -showing ways through which the organism hinders the pathological occupation of mineralocorticoid receptors by glucocorticoids leading to sodium retention and hypertension- prompted the present study on the nature of the above-mentioned extra-adrenal factors. Serotonin was chosen because of its properties as a widely distributed neurohormone, known to interact with glucocorticoids at many sites, also exhibiting increased levels and effects under stressful situations. We studied serotonin effects on 11beta-hydroxysteroiddehydrogenase 2 activity in a cell line derived from distal nephronpolarized-epithelium, employing 3H-corticosterone as substrate. The end-product, 3H- 11 -dehydrocorticosterone was separated from the substrate by HPLC and quantified. Serotonin stimulated 1I beta-hydroxysteroiddehydrogenase 2 activity only at 2nM and 25pM, the magnitude of the responsedepending also on substrate concentration. The stimulation was blocked by thespecific inhibitors methiothepin and ketanserin. We postulate that the organism partially prevents renal mineralocorticoid receptor occupancy by glucocorticoids, circulating at enhanced levels under stressful situations, through serotonin-mediated catabolic regulation of the 11beta-hydroxysteroid dehydrogenase 2 activity. Given many, mostly positive, interactions between both hormones, this might eventually pave the way to studies on a new regulatory axis.

Age-related changes in the in vivo adrenocortical production of cAMP and corticosterone in response to exogenous ACTH in long-evans female rats

Ageing effects on the in vivo cyclic 3, 5'- adenosine monophosphate [cAMP] production by the adrenal cortex were studied in the rat. Materials and Methods: Eleven old [from 23 to 29 months] and 13 young [from 4 to 5 months], dexamethasone pre-treated Long-Evans female rats received 5.0 mu.i. [1-24] ACTH/100g b.w. by intravenous injection. The plasma concentration of corticosterone as well as the adrenal contents in cAMP and corticosterone were measured, by radioimmunoassay, just before and 45 min after the [1-24] ACTH injection. Results: The basal plasma corticosterone level and the adrenal contents in corticosterone and cAMP were low and no group difference was observed. The [1-24] ACTH injection causes significant increases in the plasma corticosterone level and the glandular contents in corticosterone and cAMP, which were lesser in the old animals than in the young ones; the differences aged/young were approximately -37%, -18% and -55% respectively. Conclusions: These results suggest that the reduced stero‹dogene response of the adrenal cortex in the old rat, to an acute ACTH administration is at least partly due to a decrease in the cellular production of the principal second messenger of this hormone, i.e. the cAMP

Adrenocortical involvement during diverse stress in soft-shelled turtle Lissemys p. punctata Bonnoterre.

Adrenocortical responses to diverse stressful situations (dehydration, formaldehyde treatment and salt loading) were studied in the adult female soft-shelled turtle, Lissenmys p. punctata. Dehydration, formaldehyde treatment (formalin, 1%: 0.1 ml/100 g body weight daily) or salt loading (NaCl, 1%: 0.1 ml/100 g body weight daily) treatments consecutively for 7 days caused hypertrophy of the adrenocortical cells with their nuclear diameter increased, and depletions of adrenal cholesterol and ascorbic acid concentrations followed by decreased acid phosphatase and alkaline phosphatase activities in turtles. Corticosterone levels were elevated in both the adrenal gland and serum of turtles after dehydration and formalin stress, but the hormone level remained unaltered after salt loading in turtles. The results suggest active involvement of adrenal cortex in stress for homeostasis in Lissemys turtles.

Metabolic markers following beta-adrenoceptor agonist infusion in footshock-stressed rats

Stress hormones can alter metabolic functions in adipose tissue and liver, as well as the sensitivity of rat white adipocytes and rat atrial responses to ß-adrenergic agonists. In this study, we examined the effects of three daily footshock stress sessions on the plasma corticosterone, glucose, glycerol and triacylglycerol levels of fed, conscious male rats, and on the plasma glucose, glycerol and triacylglycerol levels of the same rats following iv infusions of ß-adrenergic agonists (isoproterenol: 0.4 nmol kg-1 min-1, noradrenaline: 5.0 æg kg-1 day-1, and BRL 37344 ([+ or -]-[4-(2-[(2-[3-chlorophenyl]-2-hydroxyethyl)amino]propyl)phenoxy]acetic acid), a selective ß3-adrenoceptor agonist: 0.4 nmol kg-1 min-1). Plasma corticosterone levels increased significantly after each stress session, while triacylglycerol levels increased after the first session and glucose increased after the second and third sessions. Glycerol levels were unaltered after stress. These results suggest that repeated footshock stress may induce a metabolic shift from triacylglycerol biosynthesis to glucose release by hepatic tissue, with glycerol serving as one of the substrates in both pathways. Stressed rats were more sensitive to infusion of noradrenaline plus prazosin and to infusion of isoproterenol, with elevated plasma glucose, glycerol and triacylglycerol levels. The higher sensitivity of stressed rats to isoproterenol and noradrenaline was probably related to the permissive effect of plasma corticosterone. Only BRL 37344 increased plasma glycerol levels in stressed rats, probably because ß3-adrenoceptors are not involved in hepatic triacylglycerol synthesis, thus allowing glycerol to accumulate in plasma

Role of dopamine in the modulation of adrenal gland responses in the osmotically stressed pigeons, Columba livia.

Salt loading on pigeons (C. livia) had stimulatory effects on brain amines (dopamine and 5-hydroxytryptamine), corticosterone, norepinephrine and epinephrine contents of adrenal gland. Conjoint administration of dopamine with hypertonic saline restored the brain amines and corticosterone of adrenal gland, but had no effect on catecholamine (CAM) contents of adrenal medulla. The excessive release of CAM in the plasma indicates sympathetic stimulation after both the treatments.

Influence of Antedorsal Thalamic nuclei on the hypophyseal-adrenal axis and cardiac beta receptors in tars submitted to vatriable chronic stress

The limbic structures play an important role in the control of the neuroendocrine and sympathical adrenal function in basal and stress conditions. This work was undertaken to evaluate plasma ACTH, adrenocortical activity, cardiac adrenoceptors density and affnity response to variable chronic stress (VCS) in anterodorsal thalamic nuclei (ADTN) lesioned rats. Thirty days after lesion, shamlesioned stressed animals increased plasma ACTH and corticosterone as compared to sham-lesioned unstressed animals (p<0.05); lesioned rats increased ACTH levels after VCS (p<0.05) as compared unstressed-lesioned rats. Whereas in sham-lesion plasma corticosterone (C) increased after stress. in lesioned animals (C) remained unchanged as compared to unstressed-lesioned animals. In the stressed groups, adrenal C contents were below those found in unstressed rats. Beta-receptors affinity, in all the experimental groups, was similar, but VCS sham-lesioned animals underwent a significant increase in cardiac D-adrenergic receptors density when compared with basal and lesioned groups (P<0.001). Our findings would demonstrate that the increment in cardiac Beta adrenoceptors density appears as a consequence of the increase in ACTH, plasma corticosterone and sympathetic response provoked by stress situations. ADTN lesion attenuated this hipophisoadrenal system response to chronic stress as well as the above mentioned cardiac beta adrenoceptors density increment.

Regulation of nephron acidification by costicosteroids

The present paper reviews work from our laboratories evaluating the importance of adrenal cortical hormones in acidification by proximal and cortical distal tubules. Proximal acidification was determined by stationary microperfusion, and measurement of bicarbonate reabsorption using luminal pH determination was performed with H+ -ion-sensitive microelectrodes. Rats were adrenalectomized (ADX) 48 h before the experiments, and corticosteroids (aldosterone(A), corticosterone(B), and 18-OH corticosterone (18-OH-B)) were injected intramuscularly 100 and 40 min before the experiments. In ADX rats stationary pH increased significantly to 7.03 as compared to sham-operated rats (6.78). Bicarbonate reabsorption decreased from 2.65 + 0.18 in sham-operated rats to 0.50 + 0.07 mmol cm-2 S(-1) after ADX. The administration of the three hormones stimulated proximal tubule acidification, reaching, however, only 47.2 per cent of the sham values in aldosterone-treated rats. Distal nephron acidification was studied by measuring urine minus blood pCO2 differences (U-B pCO2) in bicarbonate-loaded rats treated as above. This pCO2 difference is used as a measure of the distal nephron ability to secrete H+ ions into an alkaline urine. U-B pCO2 decreased significantly from 39.9 + 1.26 to 11.9 + 1.99 mmHg in ADX rats. When corticosteroids were given to ADX rats before the experiment, U-B pCO2 increased significantly, but reached control levels only when aldosterone (two 3-mug doses per rat) plus corticosterone (220 mug) were given together. In order to control for the effect of aldosterone on distal transepithelial potential difference one group of rats was treated with amiloride, which blocks distal sodium channels. Amiloride-treated rats still showed a significant reduction in U-B pCO2 after ADX. Only corticosterone and 18-OH-B but not aldosterone increased U-B pCO2 back to the levels of sham-operated rats. These results show that corticosteroids stimulate renal tubule acidification both in proximal and distal nephrons and provide some clues about the mechanism of action of these steroids.

Effect of verapamil and diltiazem on basal and acth-induced corticosterone secretion in the rat

It has been proposed that calcium plays an important role in endocrine reactions such as hormone biosynthesis, release, secretion and action on tarhet organs. The aim of this study was to evaluate the effects of the ca++ channel blockers [verapamil and diltiazem] on basal and ACTH induced corticosterone secretion in the rat. ACTH produced an increase in the plama level of both corticosterone and glucose with peak effect occurring one and two hours respectively. In this respect, administration of verapamil [20 mg kg-1; p.o.] and diltiazem 20 mg kg-1;p.o.] to rats for 8 days produced nonisgnificant change in both basal or stimulated corticosterone levels after challenge doses of ACTH [4 units kg-1 s.c.]. similarly the fasting plasma glucose level was not significantly modified by neither verapamil nor diltiazem as compared with the control group. These results suggest that the ca++ channels blocked by verapamil and diltiazem may not be directly involved in steroidogenesis, at least in the rat. Further studies may however be needed to fully characterize the role of the ca++ channels and drugs of different chemical groups which modulate such channels

Influence of anterodorsal thalamic nuclei on adrenal function in rats

La estimulación bilateral de lo núcleos anterodorsales talámicos (NADT) produjo una significativa disminución en la concentración de corticosterona plasmática y adrenal. Las ratas con lesión bilateral de NADT mostraran una mayor respuesta de corticosterona plasmática al estrés agudo que las ratas control (falsa lesión). Las ratas controles estresadas presentan valores de cortiscosterona adrenal más altos que las no estresadas mientras que en las lesionadas estresadas los valores fueron significativamente más bajos que en las lesionadas no estresadas. Las concentraciones de catecolaminas adrenalaes, Noradrenalina (NA) y Adrenalina (A), en las ratas control no se modifcan por el estrés. En las ratas lesionadas estresadas las glándulas adrenales contienen cuatro veces más de NA y dos veces más de A que las glándulas adrenales de las lesionadas no estresadas

Peso corporal y funcion adrenal en ratas con madres adoptivas desde el momento de su nacimiento / Body weigth and adrenal function in rats with foster mothers from the moment of their births

Se estudió, en ratas, el efecto de la separación de su madre sobre el peso corporal y los niveles de hormonas adrenales, corticosterona adrenal y plasmática y catecolaminas adrenales. Las crías se agruparon en lotes: a) mantenidad con su madre biológica y b) con madres intercambiada inmediatamente después del nacimiento (madrea adoptiva). Todas las ratas madres amamantaban. En el lote b, el peso corporal fue inferior (p < 0.001) al de los controles, grupo a, desde los 14 a los 28 días de edad; a partir de entonces se recupera. La concentración de corticosterona adrenal es superior (p < 0.01) en el grupo b, no así los de corticosterona plasmática que se asemejan a los del grupo control, a. Con respecto a las catecolaminas, en las ratas criadas con "madre adoptiva" los valores de noradrenalina son superiores (p < 0.001), mientras que los de adrenalina son inferiores (p < 0.01) a los de los controles

Ether and immobilization stress effects on pituitary adrenal function in hemidecorticate rats

Hemidecortication (HD) (left cerebral hemisphere) performed in rats with the aim of analyzing the modulating effect of the cerebral cortex on the hypothalamic-pituitary-adrenal axis. Corticosterone release induced either by or immobilization stress was evaluated in control (C) and HD rats. The percentage increase in corticosterone was greater in HD than in C rats after 15 min of ether stress (HD = 142%, C = 50%) and after 60 min of immobilization stress (HD = 197%, C = 126%). An in vitro test showed that the release of ACTH induced by corticotropin releasing hormone (CRH) from hemipituitary fragments from HD rats was not different from that in control rats. These results suggest an inhibitory effect of the cerebral cortex on the hypothalamus which may modulate the secretion of corticoptropin releasing peptides

Receptores para glucocorticoides y concentración de corticosterona en cerebro / Glucocorticoid receptors and corticosterone concentration in brain

El presente trabajo de investigación, presentado con el título completo de "Correlación entre receptores para glucocorticoides y concentración de corticosterona en regiones cerebrales: Sus implicancias para el estudio del estrés", fue desarrollado por las Dras. Ana María Magariños y Mónica Ferrini y el Dr. Alejandro F. de Nicola en el Laboratorio de Bioquímica Neuroendócrina del Instituto de Biológia y Medicina Experimental, cocn el apoyo de la Fundación Raquel Guedikian de Estudios sobre el Estrés. En él se analiza la concentración de corticosterona (CORT) en varias regiones cerebrales de rata y su correlación con el contenido de receptores para glucocorticoides (GC). Los resultados son importantes para localizar los sitios de acción hormonal en el cerebro durante los estados de hiperfunción adrenal, típico del estrés

Corticosterone secretion by rats after adrenalectomy

Se determinaron los niveles plasmáticos de corticosteroma de ratas en diferentes períodos después de la adrenalectomía, utilizando cromatografía líquida de alta presión (HPLC) y/o cromatografía gas-líquido (GLC). Se encontraron niveles mínimos 24 a 48 horas después de la operación