Patricia Durando

Effect of maternal separation and chronic stress on hippocampal-dependent memory in young adult rats: evidence for the match-mismatch hypothesis.

Abstract Adverse experiences early in life may sensitize the hippocampus to subsequent stressors throughout the individuals life. We analyzed in male rats, whether, the interaction between early maternal separation and chronic stress affects: (1) the volume of the dorsal hippocampus, (2) CA1, CA2/3 and dentate gyrus (DG) and (Figure 3) hippocampal-dependent memory in adulthood. Male Wistar rats were subjected to daily maternal separation for 4.5 h between postnatal days 1–21. From postnatal day 50, animals were exposed to a chronic unpredictable stress paradigm during 24 days. The volumes of the dorsal hippocampus, their areas or strata did not reveal significant differences between treatments. Non-maternally separated and stressed animals showed poor hippocampal performance in a contextual fear conditioning test, with a significant reduction in freezing behavior during post-conditioning compared with control and maternally separated and stressed animals. Also, memory retrieval 24 h after conditioning was significantly weaker in this group than in control animals. Memory performance in maternally separated and stressed rats was similar to control animals. Our results show an interaction between early environment experiences and chronic variable stress in young adulthood as evidence that early stressful experiences do not necessarily lead to a negative outcome but can help in maintaining brain plasticity and increase fitness when animals reach adulthood.

In Vitro Effect of α-MSH Administration on Steroidogenesis of Prepubertal Ovaries

Abstract The effects of α-MSH on ovarian progesterone (P) and estradiol (E 2 ) release were investigated. To this purpose, different doses of α-MSH were administered to prepubertal ovaries incubated under the following conditions: ten 5 min-pulses of perfusion medium (PM) plus LH at 160 ng/ml each one followed by a 25-min period of PM. The medium of the treated group contained α-MSH (0.1, 1, 5, or 10 μg/ml, in saline solution) and the control group saline solution. PM was assayed for P and E 2 release. The area under the curve, pulse amplitude and width, and basal hormonal release were calculated for each hormone profile. With respect to P release, an increase in the areas under the curve could be observed in ovaries treated with 1, 5 and 10 μg α-MSH/ml. This increment generally coincided with an increase in P pulse amplitude and/or basal P release. The P pulse width was not modified. No significant variations were observed in the parameters under analysis with regard to E 2 release. It is concluded that α-MSH administered to prepubertal ovaries could exert a physiological role through stimulation of P release.

Maternal separation in early life modifies anxious behavior and Fos and glucocorticoid receptor expression in limbic neurons after chronic stress in rats: effects of tianeptine.

Abstract Early-life adversity can lead to long-term consequence persisting into adulthood. Here, we assess the implications of an adverse early environment on vulnerability to stress during adulthood. We hypothesized that the interplay between early and late stress would result in a differential phenotype regarding the number of neurons immunoreactive for glucocorticoid receptor (GR-ir) and neuronal activity as assessed by Fos immunoreactivity (Fos-ir) in brain areas related to stress responses and anxiety-like behavior. We also expected that the antidepressant tianeptine could correct some of the alterations induced in our model. Male Wistar rats were subjected to daily maternal separation (MS) for 4.5 h during the first 3 weeks of life. As adults, the rats were exposed to chronic stress for 24 d and they were treated daily with tianeptine (10 mg/kg intraperitoneal) or vehicle (isotonic saline). Fos-ir was increased by MS in all structures analyzed. Chronic stress reduced Fos-ir in the hippocampus, but increased it in the paraventricular nucleus. Furthermore, chronic stress increased GR-ir in hippocampus (CA1) and amygdala in control non-MS rats. By contrast, when MS and chronic stress were combined, GR-ir was decreased in these structures. Additionally, whereas tianeptine did not affect Fos-ir, it regulated GR-ir in a region-dependent manner, in hippocampus and amygdala opposing in some cases the stress or MS effects. Furthermore, tianeptine reversed the MS- or stress-induced anxious behavior. The interplay between MS and chronic stress observed indicates that MS rats have a modified phenotype, which is expressed when they are challenged by stress in later life.

Effects of carbamazepine on cortisol levels and behavioral responses to stress in the fish Jenynsia multidentata

Carbamazepine (CBZ) is an anticonvulsant drug, prescribed worldwide for the treatment of epilepsy, bipolar disorder and trigeminal neuralgia, which has been frequently detected in aquatic environments. The objective of this study was to analyze if CBZ modifies scototaxis and shoaling behaviors and/or whole-body cortisol levels of the one-sided livebearing fish Jenynsia multidentata under stress condition. Female adults of J. multidentata were exposed to 0, 10, 50 and 200μgCBZ/L during 14days. After CBZ exposure, fish were subjected to restraint stress during 15min. Control animals were not exposed to CBZ or stress. In the light/dark preference test (scototaxis), the individuals under acute restraint stress (without CBZ) exhibited a significant increase in the mean speed and in the time spent both in the light compartment and in the bottom of the tank with respect to controls. They also showed a tendency to stay longer frozen in the light compartment. Fish exposed to 10 and 50μgCBZ/L showed a significant reduction in mean speed compared to stressed fish without CBZ. A reduction in the time spent in the bottom of the tank was also observed in fish exposed to 10μgCBZ/L. Fish exposed to 200μgCBZ/L showed a decreasing tendency in all behavioral endpoints (time spent in the light compartment, mean speed, time spent at the bottom and freezing) in comparison to stressed fish not exposed to CBZ. Considering whole-body cortisol results, fish under acute restraint stress (without CBZ) significantly increased their hormone levels with respect to the control group, while fish exposed to CBZ and acute restraint stress, significantly decreased their whole-body cortisol levels. There were no significant changes in shoaling behavior due to either stress or CBZ exposure and no significant differences in whole-body cortisol levels between experimental groups. Considering that the light/dark and shoaling tests measure different stress response behaviors regulated by different neuroendocrine systems, these results could indicate that CBZ has a differential effect on fish behavioral stress response and cortisol levels, depending on the behavioral test used and stressor applied.

Effects of α-MSH on progesterone and nitric oxide release by cultured ovarian granulosa cells in experimental rat autoimmune oophoritis

The peptide α-melanocyte-stimulating hormone (α-MSH) occurs within the pituitary, brain, skin, ovary and other tissues, and has poten anti-inflammatory activity. For this reason, we examined its effects on an autoimmune disease: the experimental autoimmune-oophoritis (EAO). We analyzed the effect of the peptide on the release of nitric oxide (NO) and progesterone from cultured ovarian granulosa (GL) cells at 0, 7, 14, 21 and 28 days after sensitization of the rats. On day 0 the progesterone levels were higher in estrous rats than those in proestrus and diestrus. The NO amount did not differ among the diverse days of the cycles. The administration of α-MSH induced a decrease of NO in estrus and diestrus, but did not affect progesterone release. The EAO rats showed a period of constant diestrus ranging from about 7 to 14 days after immunization. At the onset (day 7) and the end of this period (day 14), the NO significantly increased in estrous rats which was correlated with a reduction in progesterone concentration. This effect was reverted by α-MSH. At 21 and 28 days, progesterone release increased only when the rats were in proestrus, while NO production was similar to that on day 0. Administration of α-MSH reduced progesterone release when the rats were in proestrus and these results were correlated with an increase in NO only at day 14. The results obtained suggest that α-MSH could act as a modulator of EAO, specially when the rats are in estrus.ResumenLa hormona α-estimulante de los melanocitos (α-MSH) se puede encontrar en hipófisis, cerebro, piel, ovario y otros tejidos. Dada su potente actividad antiinflamatoria, se considera de interés el estudio de su efecto sobre una enfermedad autoinmune, la ooforitis experimental autoinmune (EAO). En este trabajo, se analiza el efecto de la α-MSH sobre la liberación de óxido nítrico (NO) y progesterona por células granulosas (GL) ováricas en cultivo a los 0, 7, 14, 21 y 28 días posteriores a la inmunización de las ratas. En el día 0 del tratamiento, los niveles de progesterona son mayores en ratas en estro que en proestro y diestro, mientras que los de NO no muestran diferencias. La administración de α-MSH produce disminución de la producción de NO en ratas en estro y diestro, sin que se observen cambios sobre la progesterona. La inmunización induce un periodo de diestros continuos que se extiende aproximadamente entre los días 7 y 14 del periodo experimental. Al inicio y al final de este período, los niveles de NO aumentan y los de progesterona disminuyen cuando las ratas se encuentran en estro, siendo revertido este efecto por α-MSH. La producción de progesterona se incrementa a los 21 y 28 días sólo cuando las ratas se encuentran en proestro, lo que es revertido por α-MSH. Los datos obtenidos sugieren que la α-MSH actuaría como un modulador del desarrollo de la OEA, fundamentalmente cuando las ratas se encuentran en estro.

Differential effects of tianeptine on the dorsal hippocampal volume of rats submitted to maternal separation followed by chronic unpredictable stress in adulthood

Abstract Early maternal separation (MS) may produce lasting effects in the dorsal hippocampus (DH) that can change its response to chronic stress in adulthood. Chronic stress affects DH morphology and function, but tianeptine (an anti-depressant) can reverse the stress-induced morphological impairments. Morphologic alterations of hippocampus can affect contextual memory. Therefore, we evaluated the effect of tianeptine in MS and chronically stressed rats on: 1) volume of the DH and its areas using stereology and 2) hippocampal-dependent memory using a fear conditioning test. Male Wistar rats were subjected to daily MS for 4.5 h between postnatal days (PND) 1–21, or to animal facility rearing (AFR). Between (PND) days 50 and 74, rats were exposed to chronic unpredictable stress and were treated daily with tianeptine (10 mg/kg) or vehicle, providing eight groups: AFR-unstressed/vehicle (n = 5 for stereology, n = 18 for fear conditioning test); AFR unstressed/tianeptine (n = 6 and n = 10); AFR-chronic stress/vehicle (n = 6 and n = 14); AFR-chronic stress/tianeptine (n = 6 and n = 10), MS-unstressed/vehicle (n = 5 and n = 19), MS-unstressed/tianeptine (n = 6 and n = 10), MS-chronic stress/vehicle (n = 6 and n = 18), and MS-chronic stress/tianeptine (n = 6 and n = 10). MS-chronic stress/tianeptine rats showed a diminished CA1 area than the corresponding MS-unstressed/tianeptine rats. The combination of stressors produced a freezing response similar to those of the control group during postconditioning. During retrieval, MS led to a diminished freezing response compared to the AFR-unstressed groups. Tianeptine had no effect on freezing behavior. Our results show that tianeptine can affect the CA1 area volume differently depending on the nature and quantity of stressors but cannot alter freezing to context.

A double-hit model of stress dysregulation in rats: implications for limbic corticosteroid receptors and anxious behavior under amitriptyline treatment

Abstract Adversity during early life can lead to diverging endocrine and behavioral responses to stress in adulthood. In our laboratory, we evaluated the long-term effects of early life adversity and its interaction with chronic stress during adulthood. We propose this as a model of vulnerability to dysregulation of the stress response. We hypothesized that rats subjected to both protocols would show differential expression of corticosteroid receptors measured as number of neurons immunoreactive for glucocorticoid receptors (GR) or mineralocorticoid receptors (MR), in limbic areas related to the control of anxiety-like behavior. We also evaluated the effect of amitriptyline expecting to prevent the outcomes of the model. Male Wistar rats were separated from the mother (MS) for 4.5 h every day for the first 3 weeks of life. From postnatal day 50, rats were subjected to chronic variable stress (CVS) during 24 d (five types of stressor at different times of day). During the stress protocol, the rats were administered amitriptyline (10 mg/kg i.p.) daily. MS evoked lower MR expression in the central amygdaloid nucleus and this was reversed by amitriptyline. Furthermore, CVS increased MR immunoreactivity in the hippocampal area CA2 and increased anxious behavior; both effects were prevented by the antidepressant. When MS was combined with CVS during adulthood, there was a reduction of locomotor activity, with no corrective effect of amitriptyline. The differential effects among groups could mean that MS would promote an alternative phenotype that is expressed when facing CVS (a double hit) later in life.