The effect of chronic stress on prenatal development of the central nervous system.

The survival of developing embryos depends on the control and maintenance of homeostasis. Stress caused by chronic immobilization during pregnancy in rats may alter the normal development of the nervous system and increase susceptibility to psychiatric disorders. We investigated the effects of chronic stress on cell proliferation in the forebrains of embryos at 12 days of gestation, and in the hippocampus, dentate gyrus and cortex in embryos at 17 and 21 days of gestation. We examined serial sections of the embryonic brains of control and stressed rats at days 12, 17 and 21 of gestation. Brain sections were immunolabeled with anti-PCNA and stereological analysis was performed on 540 images. The results showed no statistical differences on days 12 and 17 of gestation in the proliferation area of the structures studied, whereas on day 21 of gestation, proliferation decreased in the cortex and dentate gyrus of embryos of the stressed group. These changes were related to decreased prolactin and increased corticosterone concentrations in the plasma.

Chronic stress and its effects on adrenal cortex apoptosis in pregnant rats.

The model of chronic intermittent stress by immobilization during pregnancy may produce alterations in the mechanisms that maintain adrenal gland homeostasis. In earlier investigations using this model, significant variations in plasma prolactin and corticosterone levels, and adrenal gland weights were observed. We hypothesized that chronic stress causes changes in apoptosis in the adrenal glands of pregnant rats. We identified and quantified apoptotic cells in the adrenal cortex and examined their ultrastructural characteristics using transmission electron microscopy. Adrenal glands of pregnant rats at gestation days 12, 17 and 21 were studied for control and experimental (stressed) rats. Immunolabelling techniques, stereological analysis and image quantification of adrenal gland sections were combined to determine differences in apoptosis in the different cell populations of the adrenal cortex. The apoptotic index of the experimental rats showed a significant reduction at gestation day 17, while at days 12 and 21 there were no differences from controls. Moreover, the apoptotic index of the reticular zones in control and experimental animals showed a significant increase compared to the glomerular and fascicular zones at the three gestation times studied. Chronic stress by immobilization reduced the caspase-dependent apoptotic index at gestation day 17, which may be related to variations in plasma concentrations of estrogens and prolactin.

Reproductive response in offspring male rats exposed to prenatal stress and to early postnatal stimulation / Respuestas reproductivas en ratas estresadas prenatalmente, expuestas a estimulación postnatal

Stress in pregnant rats alters the pattern of secretion of corticosterone (COR) and modifies transplacentally hypothalamic-pituitary-adrenal axis (HPA) fetus. Prenatal stress during the critical hypothalamic differentiation is related to decreased fertility of male offspring by an increase in the basal level of COR. This modification could induce long-term changes in the process of apoptosis in the testis. However, early postnatal handling increases maternal behavior and could reverse the effects caused by increased secretion of COR. The aim of this research was to investigate the effects of early postnatal stimulation of male rats prenatal stressed by chronic immobilization during the last two weeks of pregnancy, on the hypothalamic-pituitary-gonadal axis and their relationship with the activity of the HPA. Male Wistar rats 3 month olds, were separated in four groups: (a) prenatally stressed animals by immobilization (IMO), without postnatal stimulation; (b) prenatally stressed animals with postnatal stimulation; (c) control animals without prenatal stress, without postnatal stimulation and (d) control animals without prenatal stress, with postnatal stimulation. In different animals groups plasmatic levels of COR, Testosterone (T) and Luteinizing Hormone (LH) were analyzed. Gonadosomatic index and testicular apoptosis was determined. In conclusion that prenatal stress by IMO increased levels of COR and inhibits the HHG axis obtaining low values of plasmatic LH and T, testicular weight, and induction of apoptosis in testes. On other hand, early postnatal stimulation results in an increase in maternal care to the offspring reversing the effects of prenatal stress on the HPG axis. This effect could be mediated by a mechanism independent of the HPA axis.

El estrés en ratas preñadas altera el patrón de secreción de corticosterona (COR) materna la cual, por vía transplacentaria, produce una alteración del eje Hipotálamo-Hipófiso-Adrenal (HHA) fetal. El estrés prenatal producido durante la etapa crítica de diferenciación hipotalámica, está relacionado con la disminución de la fertilidad en las crías macho, por un aumento en el nivel de COR basal. Esta modificación podría inducir cambios a largo plazo en el proceso de apoptosis testicular. Sin embargo, la estimulación postnatal temprana mejora el comportamiento materno, revirtiendo las alteraciones producidas por el aumento de COR en las crías adultas. El objetivo fue investigar el efecto de la estimulación postnatal temprana sobre el eje Hipotálamo-Hipófiso-Gonadal (HHG) en ratas macho estresadas prenatalmente (EP), por inmovilización crónica durante las dos últimas semanas de la preñez. Se utilizaron crías de 3 meses de edad, que fueron divididas en 4 grupos: (a) individuos EP y sin estimulación postnatal; (b) individuos EP con estimulación postnatal; (c) individuos controles no estresados prenatalmente (CP) y sin estimulación postnatal; y (d) individuos CP con estimulación postnatal. En todos los grupos se midió COR, Testosterona (T) y Hormona Luteinizante (LH). Se determinaron la apoptosis y la Caspasa 3 testicular y el índice gonadosomático. Se concluye que el estrés prenatal por inmovilización aumenta los niveles de COR del eje HHA e inhibe el eje HHG obteniendo valores bajos de LH y T plasmáticas. Se observa disminución del tamaño testicular y aumento de la apoptosis de las células testiculares. Por otro lado, la estimulación postnatal temprana se traduce en un aumento del cuidado materno hacia la cría, lo que revierte los efectos producidos por el estrés prenatal sobre el eje HHG. Este efecto podría estar mediado por algún mecanismo independiente del eje HHA.

Effects of prenatal stress on male offspring sexual maturity

Prenatal stimulations have been shown to have long-term effects on at reproductive activity. We evaluated the influence of the prenatal stress on the hypothalamic-pituitary-gonad (HPG) axis in male offsprings from mothers with high number of offsprings per litter (HNL) and low number of offsprings per litter (LNL) after hypothesizing that the number of offsprings per litter may modify the effect of the prenatal stress on the HPG of adult offsprings. Pregnant Wistar rats were used for this study. Immobilization (IMO) stress was used, 30 min, 3 times per week, from the 5th to 21st day of pregnancy. The weight of adrenal and gonads, and the corticosterone (COR), testosterone (TES) and luteinizing hormone (LH) plasmatic levels were analyzed in the male offspring at 30, 45 and 70 days of age. The offspring males coming from LNL showed a decrease in testicle weight and TES levels, without changes in the plasmatic LH levels. However, the offspring of HNL showed a decrease of LH levels. It is possible to conclude that in LNL prenatal stress would produce alterations to gonadal level, while in HNL the effect of stress would be evident at pituitary level.

Relative Concentrations of Placental Lactogen II and PRL-Like Protein-A in Stressed Rats Placenta / Concentraciones del Lactógeno Placentario II y la Proteína A Ligada a Prolactina en Placentas de Ratas Estresadas

The chronic stress induces functional adaptations in the hypothalamo-pituitary- adrenocortical (HPA) and in the sympathetic-medullary-adrenal axis (SAM). Both axis are considered vital regulators of the homeostasis in vertebrates (Seyle, 1936; Ostrandrer et al, 2006. On the other hand, the placenta provides highly specialized functions during gestation that are critical for the normal development of the embryo/fetus (Soares et al., 1991). We hypothesized that the chronic immobilization (IMO) stress in pregnancy rats produces alterations in prolactin concentrations in placental tissue and also changes in the response of SAM axis. Chronic stress by IMO was applied on days 12, 17 and 21 of pregnancy rats. Relative concentrations and localization of placental lactogen-II (PL-II) and the PRL- like protein A (PLP-A) in chorioalantoic placenta were estimated by Immunoblotting and Immunocytochemical analysis. The levels of catecholamines metabolite, acid 3-metoxi 4-hidroximandélico (VMA), were analyzed in stressed rats urines on 6,12,17,21 days of pregnancy, by HPLC, in order to determine the response of SAM axis. During the days of the pregnancy studied, chronic stress did not induce any changes neither in the localization nor in placental concentrations of PL-II and PLP-A. The VMA values in stressed mothers urines increased on the day 6 respecting the control ones at the same time of pregnancy. VMA values in stressed rats at 21 days of pregnancy are smaller than the respective controls. We conclude that the chronic stressed mothers activated the SAM axis at the beginning of pregnancy and then they diminished the metabolites catecholamines that were interpreted as a stress adaptation coincident with normal concentrations of both placentary prolactines at this stage of the pregnancy.

El estrés crónico induce adaptaciones funcionales en los ejes hipotálamo-pituitario-adrenal (UPA) y en el simpático médulo adrenal (SAM). Ambos ejes son considerados reguladores vitales de la homeostasis en los vertebrados (Seyle, 1936; Ostrandrereí al., 2006). Por otro lado, el desarrollo y crecimiento fetal de los mamíferos dependen en gran medida del buen funcionamiento de la placenta (Soares, 1991). Nosotros hipotetizamos que el estrés crónico por inmovilización (IMO) aplicado a las ratas gestantes produce alteraciones en las concentraciones de las prolactinas en el tejido placentario y cambios en la respuesta del eje SAM. Se le aplicó estrés crónico por IMO a las hembras en los días 12, 17 y 21 de la preñez y se analizó por inmunocitoquímica e inmunoblotting la localización y concentraciones del lactógeno placentario dos (PL-II) y la proteína A ligada a la prolactina (PLP-A) en la placenta. Se analizaron por HPLC, en las orinas de ratas preñadas (6,12,17,21 días), los niveles del metabolito de las catecolaminas, (ácido 3-metoxi 4-hidroximandélico) (VMA), a fin de determinar la respuesta del eje SAM al tratamiento. El estrés crónico no indujo cambios tanto en la localización como en las concentraciones de PL-II y PLP-A en las placentas en los días de la preñez estudiados. Los valores de VMA en las orinas de las madres estresadas se incrementaron en el día 6 con respecto al control del mismo tiempo de preñez. Mientras que a los 21 días los valores de VMA de las ratas estresadas son menores que los controles respectivos. Concluimos que en las madres estresadas crónicamente, no se alteraron las concentraciones de ambas prolactinas placentarias. En cambio se activó el eje SAM al comienzo de la preñez ante el primer estímulo estresante y luego una reducción de la respuesta del eje ante el estrés crónico, a medida que avanza la preñez.

Chronic stress effects on the apoptotic index of the adrenal cortex of pregnant rats

Chronic stress by immobilization during gestation can alter several mechanisms that maintain homeostasis in adrenal gland. The aim of this work was to quantify the apoptotic index of adrenal cortex during mid-pregnancy and to prove cytological characteristics by electron microscopy. The apoptotic index did not present significant differences between the adrenal cortex areas of control and experimental rats in any of the three ages studied. The day of gestation influenced significantly on the apoptotic index in both groups. This index increased as gestation progressed. It may be concluded that chronic stress by immobilization might induce the increase of apoptotic index in adrenal cortex as gestation progresses which might be related variations of plasmatic corticosterone and prolactin, and to the decrease of specific growth factors. On the other hand, it might be concluded that each zone of adrenal cortex behaves independently in regards to apoptosis and cellular proliferation via paracrine and/or autocrine regulatory mechanisms without being affected by other zones.

Renal mechanisms involved in stress-induced antinatriuresis and antidiuresis in rats.

The present study was conducted to investigate if changes in sodium and water excretion in stressed animals were due to modifications in the glomerular filtration rate (GFR) and to determine the participation of angiotensin II (Ang II) and alpha and beta-adrenoceptors on sodium and water renal excretion in rats subjected to immobilization stress (IMO). Male Wistar rats (250-300 g) were randomly separated into five different groups and vehicle (0.9% NaCl) via intraperitoneal (i.p.) or propanolol (3 mg/kg i.p.) or captopril (6 mg/kg i.p.) or yohimbine (3 mg/kg i.p.) or prazosin (1 mg/kg i.p.) were injected respectively. During experimental measurements, the animals were kept in metabolic cages for 6 h and sodium, potassium and water renal excretion and saline (1.5% NaCl) and water intake were determined at day 1 (drug effect) and day 7 (drug + IMO effects). GFR was measured by creatinine clearance in control and IMO rats. A stress-induced antinatriuresis and antidiuresis was reversed by alpha 1 and alpha 2-adrenoceptor antagonists, while captopril inhibited only the antidiuresis and propranolol had no effect on either parameter. No differences were observed in creatinine clearance in the studied groups. Since yohimbine blocks alpha 2-adrenoceptors and prazosin blocks alpha 1-adrenoceptors and alpha 2B-adrenoceptors, the stress-induced renal sodium reabsorption mainly could be attributed to alpha 2B-adrenoceptors. The present results indicate that beta-adrenoceptors do not participate in this response and, Ang II only reverses the antidiuresis and shows a slight participation in antinatriuresis. The increment in sodium and water reabsorption caused by IMO occurred without changes in the glomerular filtration rate.

Renal excretion and saline intake during post-stress immobilization period in rats.

An experiment in which the rats access either to 0.5% or 1.5% saline was designed in order to further characterise the relationship between sodium intake and renal excretion after acute immobilization stress. A saline solution for 3 days was provided to the rats previous to the experimental day. On that day, after finishing acute immobilization stress, all variables under observation were measured every 6 h for 24 h. These periods were denominated as follows: T1 (12.00 to 18.00 h), T2 (18.00 to 24.00 h), T3 (24.00 to 06.00 h) and T4 (06.00 to 12.00 h). Acute immobilization stress reduced sodium renal excretion in both T1 and T2. Sodium intake in acute immobilization stress rats was lower than in control rats during all observed periods, while the urine volume was only reduced in the stressed animals in T1. These results were similar in both saline solution concentrations. A good correlation was observed between sodium intake and sodium excretion in control rats having access to either 0.5% or 1.5% saline as well as in stressed rats having access to 0.5% saline, this correlation was not observed in stressed rats with 1.5% saline. This suggests that stress impaired the renal capability of rats to handle high sodium but not a slight sodium overload. The inability of the kidney to excrete sodium may be critical to reduce sodium intake after acute immobilization stress.

[Cholesterolemia and arterial pressure levels. Relationship with different chronic stress configurations]. / Niveles de colesterolemia y de presión arterial. Su relación con diferentes configuraciones de estrés crónico.

Several experimental studies refer to the relationship between chronic stress, cholesterolaemia levels and variations in the arterial blood pressure. Our objective is to establish a significant statistical correlation between stress factors, hypertension and hypercholesterolaemia in the studied people. 146 agents were tested among teachers an others employees from the National University of Río Cuarto, who voluntarily went clinical control, reporting data such as arterial pressure, cholesterolaemia, patholgoic records; an standized survey was done considering potentially stress factors, grouped in four different types of stress: (1)-psychoalimentary, (2)-pure psychic, (3)-laboral, (4)-psychofamiliar, giving each of them a value whose addition gane a stress potential factor. The results show that 45.89% of the people studied have hypercholesterolaemia (higher 200 mg% with a mean 237.09 +/- 29.97) being significantly higher (P = 0.001) in the group of employees older than 40 years old., 7.53% of the people showed high arterial pressure, and the 90.90% of this people have hypercholesterolaemia. The hypercholesterolaemic group showed a marked incidence of stress rates higher, with respect to the total people in the four types of stress studied. Significative higher values were observed in the laboral and familiar stress types coinciding with the hypertense group of individuals. According to the collected data we conclude that the relationship between cholesterolaemia, arterial pressure and chronic stress varies with the different types of stress considered, and seem adequate index of stressors levels of studied people.

Chronic immobilization stress reduces sodium intake and renal excretion in rats.

The influence of chronic exposure to immobilization (IMO) on sodium appetite as well as sodium and potassium renal excretion in adult male Wistar rats was studied. The animals were individually housed and all variables under observation were measured in metabolic cages the first, seventh, and thirteenth days once the experiment had started. Half of the rats had access to water, and the remainder of the rats had access to both water and saline solution (1.5% NaCl). IMO reduced the intake of saline solution. Renal water, sodium, and potassium excretion in those IMO rats having access to saline were lower than in control rats. The effects of IMO were very similar during all observation days; therefore no evidence of adaptation to repeated stress was found. The present data indicate the following: (i) IMO stress reduced sodium appetite, probably as a secondary effect to the deficit in sodium renal excretion; (ii) IMO caused antidiuresis and antikaliuresis, only in those rats taking saline solution; (iii) no adaptation to repeated IMO stress was found in any of the tested variables. The reduction of sodium appetite observed in stressed rats might be a homeostatic mechanism to maintain sodium balance after impairment of renal sodium excretion caused by stress.

[Effects of parathion on acetylcholinesterase activity in rat kidney]. / Efectos del paration sobre la actividad de acetilcolinesterasa en riñón de rata.

In this work the effects of parathion (a competitive acetylcholinesterase inhibitory agent) on the enzyme activity was studied by cytochemical methods in the kidney of rats; being the doses used not inhibitory of red blood cells acetylcholinesterase (subtoxic dose). Two groups of rats were used: control (CR) and parathion-treated (TR) groups, both submitted to a water deprivation period of 24 h. for induction of primary thirst. The treated-rats group received parathion i.p. at doses of 600 micrograms/100g body weight. For demonstration of acetylcholinesterase activity, renal tissue incubation was performed by the Karnovsky and Roots method with the Tsuji Larabi variation. The results of the five assays of incubation enable us to conclude that there exists a noticeable activity of acetylcholinesterase in the renal cortex of control rats, which is blocked by subtoxic doses of organophosphorus pesticide. We suggest that the natriuretic effect of parathion can be explained by this mechanism.

Atropine enhancement of aldosterone induced renal sodium reabsorption in dogs.

The aim of the present study was to investigate the effect of atropine on renal tubular membranes, as we suggested in a previous work. Mongrel dogs were anesthetized and i.v. infused with isotonic NaCl solutions. Ureters were catheterized and urine samples collected every 10 minutes. Different groups of dogs received single i.v. doses of aldosterone (2 and 4 ug/kg body wt); atropine (1 ug/kg body wt); atropine prior to the low dose of aldosterone; and saline solution (1 ml). The administration of atropine prior to the low dose of aldosterone enhanced the antinatriuretic effect of the latter and furthermore produced an anticipation in time for the effect. The results obtained seem compatible with an atropine effect producing changes in the tubular membranes modifying its permeability or transport capacity.