The effect of different maternal deprivation paradigms on the expression of hippocampal glucocorticoid receptors, calretinin and calbindin-D28k in male and female adolescent rats
Highlights
► We compare three different maternal deprivation (MD) paradigms in this study. ► We examine changes in the hippocampal expression of three proteins in rats on PND21. ► They were glucocorticoid receptors (GRs), calretinin (CALR) and calbindin-D28k (CALB). ► All the three proteins were much more abundantly expressed in females than in males. ► MD paradigms affected CALR and CALB in both genders but affected GRs only in males.
Introduction
Both animal and human behavioral studies have shown that the brain is particularly sensitive to stress during early childhood. Stressful events that occur during this time may induce permanent alterations in neurodevelopment (Plotsky and Meaney, 1993) that may in turn be associated with an increased risk of psychopathology during adulthood (Heim and Nemeroff, 1999, Heim and Nemeroff, 2001). Maternal deprivation (MD) has proven to be an adverse event that can induce significant stress responses in rat pups, even during the stress hyporesponsive period (SHRP) (Lephart and Watson, 1999, Lupien et al., 2009). The maternal deprivation paradigm, which involves the single or repeated separation of newborn pups from their dam for a specific period of time, is a well-established protocol that is used to investigate neurochemical changes associated with the etiology of and vulnerability to psychiatric diseases in animal models (Cirulli, 2003).
Stress triggers the activation of the hypothalamus–pituitary–adrenal (HPA) axis, culminating in the production of glucocorticoids (GCs) by the adrenal glands. An abnormally high level of GCs negatively impacts the functioning of brain regions that regulate GC receptor levels (Csernansky et al., 2006, de et al., 2005, Elgh et al., 2006, Eliner et al., 1995, Lephart and Watson, 1999, Mizoguchi et al., 2008). Because of the high number of glucocorticoid receptors (GRs) located there, one area of the brain that is particularly sensitive to stress and stress-related hormones is the hippocampus, which is involved in learning and memory, behavioral adaptation and regulation of the HPA axis.
An increase in the number of GRs has also been shown to regulate Ca2+ influx into neurons (Karst and Joëls, 2007, Thibault et al., 2007). Calretinin (CALR) and calbindin-D28k (CALB) are two calcium-binding proteins that are implicated in neurogenesis and neuronal survival. They are both widely expressed throughout the nervous system and are considered to be modulators of intracellular calcium concentration (Müller et al., 2005, Schwaller et al., 2002). A recent study demonstrated that that the density of both CALR and CALB increases in the hippocampus of maternally deprived rats when compared to controls (Gruss et al., 2008).
However, the mechanism underlying stress-induced, Ca2+-related neurobiochemical changes in the hippocampus remains unknown. Although the psychophysiological effects of adverse stimuli (such as MD) are well documented in animals, neither the minimum effective intensity of these stimuli nor the molecular basis of their action has been addressed. In this study, we investigated the contribution of the timing and duration of the MD paradigm on stress-induced hippocampal changes in rats. Both GRs and calcium-binding proteins have been reported to play a crucial role in the stress response in rats, and there are no previous data regarding possible alterations in the expression of these proteins when rats of both genders are subjected to different MD paradigms; therefore, we studied the effects of different MD paradigms on the expression of hippocampal GRs, CALR and CALB during the SHRP in male and female adolescent rats.
Section snippets
Animals and maternal deprivation paradigms
Pregnant Sprague–Dawley rats were housed in single cages (40 × 25 × 20 cm) under controlled conditions of temperature (21 ± 1 °C), humidity (55 ± 5%) and light (12-h light/dark cycle beginning at 8:00) and were allowed free access to food and water. They were checked for litters daily. The day of birth was designated as postnatal day zero (PND0). All pups were weaned at PND21 and subsequently housed in sex-matched groups of eight per cage (40 × 25 × 20 cm).
Each litter was randomly assigned as a whole to one
GR expression in the hippocampus
As shown in Fig. 1, GR levels were significantly higher in female vs. male rats [F(1,47) = 63.29, p < 0.001]. Male rats in groups MD and MD9 experienced a significant upregulation of GR when compared to controls (p < 0.05 and p < 0.001, respectively); however, no significant change in GR expression was found among female rats that underwent any of the maternal deprivation paradigms (Fig. 1A and B).
CALR expression in the hippocampus
CALR expression in the hippocampus of male rats was significantly lower than in female rats [F(1,47) = 74.8,
Discussion
The secretion of GC hormones is governed by the activation of the hypothalamic–pituitary–adrenal (HPA) axis during a stressful situation. Our data demonstrated that the abundance of GRs in the hippocampus of female rats was significantly higher than males at PND21, which might be attributed to the greater influence of female-specific gonadal steroids. Females predominantly produce estrogens, whereas androgens are the major sex hormone in males. Female laboratory rodents tend to secrete higher
References (40)
Early disruption of the mother–infant relationship: effects on brain plasticity and implications for psychopathology
Neurosci. Biobehav. Rev.
(2003)- et al.
Cognitive dysfunction, hippocampal atrophy and glucocorticoid feedback in Alzheimer’s disease
Biol. Psychiatry
(2006) - et al.
Early maternal deprivation as an animal model for schizophrenia
Clin. Neurosci. Res.
(2003) - et al.
Corticosterone impairs hippocampal neuronal calcium regulation—possible mediating mechanisms
Brain Res.
(1993) - et al.
Sex differences in cell proliferation, cell death and defensive behavior following acute predator odor stress in adult rats
Brain Research
(2003) - et al.
Maternal deprivation and early handling affect density of calcium binding protein-containing neurons in selected brain regions and emotional behavior in periadolescent rats
Neuroscience
(2007) - et al.
Maternal separation during a specific postnatal time window prevents reinforcement of hippocampal long-term potentiation in adolescent rats
Neuroscience
(2008) - et al.
The impact of early adverse experiences on brain systems involved in the pathophysiology of anxiety and affective disorders
Biol. Psychiatry
(1999) - et al.
The role of childhood trauma in the neurobiology of mood and anxiety disorders: preclinical and clinical studies
Biol. Psychiatry
(2001) Corticosteroids in relation to fear, anxiety and psychopathology
Neurosci. Biobehav. Rev.
(2001)
Anxiolytic-like effects of selective mineralocorticoid and glucocorticoid antagonists on fear-enhanced behavior in the elevated plus-maze
Psychoneuroendocrinology
Dimorphic expression of calbindin-D28K in the medial basal hypothalamus from perinatal male and female rats
Dev. Brain Res.
Maternal separation: hypothalamic-preoptic area and hippocampal calbindin-D28K and calretinin in male and female infantile rats
Neurosci. Lett.
Role of resocialization and of 5-HT1A receptor activation on the anxiogenic effects induced by isolation in the elevated plus-maze test
Physiol. Behav.
Calcium as sculptor and destroyer of neural circuitry
Exp. Gerontol.
Suppression of glucocorticoid secretion enhances cholinergic transmission in rat hippocampus
Brain Res. Bull.
Alterations in hippocampal calcium-binding neurons induced by stress models of depression: a preliminary assessment
Pharmacol. Rep.
Maternal separation in neonatal rats elicits activation of the hypothalamic-pituitary-adrenocortical axis: a putative role for corticotropin-releasing factor
Psychoneuroendocrinology
Early, postnatal experience alters hypothalamic corticotropin-releasing factor (CRF) mRNA, median eminence CRF content and stress-induced release in adult rats
Brain Res. Mol. Brain Res.
Housing familiar male wildtype rats together reduces the long-term adverse behavioural and physiological effects of social defeat
Psychoneuroendocrinology
Cited by (13)
Sex-dependence and comorbidities of the early-life adversity induced mental and metabolic disease risks: Where are we at?
2022, Neuroscience and Biobehavioral ReviewsThe impact of early life stress on the central oxytocin system and susceptibility for drug addiction: Applicability of oxytocin as a pharmacotherapy
2020, Neuroscience and Biobehavioral ReviewsCitation Excerpt :When rodent pups underwent MD for 24 h ranging from PND 3 to PND 20, ACTH and cortisol plasma levels were higher basally and following exposure to an additional stressor when compared to pups that were not maternally deprived (Stanton et al., 1988; Rots et al., 1996; Dent et al., 2000; Avishai-Eliner et al., 1995). Whilst the MD paradigm is a valid model for schizophrenia when conducted at PND 9 (Xu et al., 2011), it appears that a single 24 h episode of MD at any point across the first three weeks of life is sufficient to elicit changes in the HPA axis that are consistent with the MS and NI models of early life stress. The early postnatal stress models discussed thus far have involved either single or intermittent exposure to early life stress.
Suppressed Calbindin Levels in Hippocampal Excitatory Neurons Mediate Stress-Induced Memory Loss
2017, Cell ReportsCitation Excerpt :This transient increase falls in a critical developmental period of the hippocampus (Liao et al., 2014; Liu et al., 2016). Similar to previous findings (Seidel et al., 2008; Xu et al., 2011), we found that stress exposure during this critical period reduced calbindin levels in subtypes of CA1 and DG neurons in adulthood. Although inconsistent results have been reported (Giachino et al., 2007), these and our data are not mutually exclusive considering the differences in experimental animals and stress paradigms.
The maternal deprivation animal model revisited
2015, Neuroscience and Biobehavioral ReviewsCitation Excerpt :Regarding the proposed effect on intracellular Ca2+ levels it is worth mentioning that MD has also been reported to affect the expression of certain calcium-binding proteins, in particular, Calretinin (CALR) and Calbindin (CALB), two modulators of intracellular calcium concentration that are widely expressed in the nervous system (Muller et al., 2005; Schwaller et al., 2002). Xu et al. (2011) reported sex dependent changes in the expression levels of these two proteins, with effects being significant exclusively for females among which an increase in CALR levels was observed as well as a marked decrease in CALB expression levels (Xu et al., 2011). However, further studies are needed to dissect the neurobiological targets of the increase in corticosterone during this critical neonatal period, i.e. SHRP.
Maternal deprivation effects on brain plasticity and recognition memory in adolescent male and female rats
2013, NeuropharmacologyCitation Excerpt :More recently, sex differences in the effects of MD in the hippocampal expression of calcium-binding proteins (calretinin and calbindin) have been reported. MD provoked an increase in both calretinin and calbindin proteins in the hippocampus of males, while MD females experienced an increase in calretinin levels but a notable decrease in calbindin expression (Xu et al., 2011). Since a decline in calbindin levels may represent alterations in the neuroprotective properties against apoptosis (Nowak et al., 2010), this sexually dimorphic effect may account for the presently observed sex differences in NeuN expression, and consequently in the differential effects of MD on males and females' cognitive function.
Maternal Deprivation in Rats Decreases the Expression of Interneuron Markers in the Neocortex and Hippocampus
2021, Frontiers in Neuroanatomy