WITHDRAWN: Developmental regulation and lateralization of GABA receptors in the rat hippocampus

Maternal exposure to silicon dioxide nanoparticles reduces hippocampal neurogenesis and synaptogenesis and induces neurodegeneration in rat offspring hippocampus

Silicon dioxide nanoparticles (SiO₂-NPs) are among the most widely used nanoparticles because of their chemical-physical properties. Since most brain maturation occurs in the neonatal period in humans and many mammals, it is important to understand how NPs may affect this process. This study tested the hypothesis that SiO2-NPs from treated dams could affect the hippocampus of neonatal rats during lactation. Twenty-four pregnant rats, after delivery, were divided into three groups of control, SiO₂-NPs (25 mg/kg) and SiO₂-NPs (100 mg/kg). The rats were treated from 2^nd to 21^st days post-delivery by gavage and the effects of these NPs were evaluated in the offspring's hippocampi to reveal the effects of maternal exposure to SiO₂-NPs during lactation on the offspring's hippocampi. The offspring in the SiO₂-NPs groups had higher malondialdehyde concentration and lower antioxidant activity in the hippocampi than the non-treated control group. The mean number of doublecortin positive (DCX⁺) cells and synaptophysin expression in the hippocampi of the SiO₂-NPs groups were significantly lower than the control group, whereas the mean number of dark neurons was significantly higher. Also, animals in the SiO₂-NPs groups had a weak cognitive performance in adulthood. In conclusion, maternal exposure to SiO₂-NPs via breastfeeding could affect offspring's hippocampal neurogenesis and synaptogenesis, leading to impaired cognitive performance.

Laterality and sex differences in the expression of brain-derived neurotrophic factor in developing rat hippocampus

Brain-derived neurotrophic factor (BDNF), as a member of neurotrophin family, plays an important role in neurogenesis, neuronal survival and synaptic plasticity. BDNF is strongly expressed in the hippocampus, where has been associated with memory consolidation, learning, and cognition. In this study, Real-time PCR, immunohistochemistry, and stereology were used to evaluate the gender differences and left-right asymmetries in the expression of BDNF in the developing rat hippocampus during the neurogenesis-active period, at postnatal days P0, P7 and P14. We found the lowest expression of BDNF in the right side and the highest in the left side hippocampi of both male and female neonates at P14 (P ≤ 0.05 each). At the same time, there were significant differences in the hippocampal expression of BDNF between males and females (P ≤ 0.05 each). No important differences in the number of BDNF expressing neurons in different subregions of right/left hippocampus were observed between male and female animals at P0 and P7 (P > 0.05). Furthermore, the highest numerical density of BDNF positive cells was detected in the both sides hippocampal CA₁ in the male/female offspring at P7, and in the CA₂, CA₃ and dentate gyrus at P14 (P ≤ 0.05 each). Based on these findings, it can be concluded that there are prominent sex and interhemispheric differences in the expression of BDNF in the developing rat hippocampus, suggesting a probable mechanism for the control of gender and laterality differences in development, structure, and function of the hippocampus.

The protective role of alpha-lipoic acid on the appearance of fibronectin and laminin in renal tubules following diazinon exposure: An experimental immunohistochemical study

Extracellular matrix (ECM) exerts a major role in maintaining the structure and developmental processes of tissues. To form the tubular basement membrane in the kidney, sulfate proteoglycans, collagen, laminin, fibronectin, and other glycoproteins congregate in the ECM. As an insecticide, diazinon (DZN) may alter the proportion of ECM by cholinesterase activity inhibition and oxidative stress. The naturally, alpha-lipoic acid (ALA) plays an effective and therapeutic role in the treatment of toxicities and diseases in the body. In the current study, an attempt was made to evaluate the impacts of alpha-lipoic acid on the distribution of fibronectin and laminin in the renal tubules of male Wistar rats following exposure to diazinon. In this study, the animal groups comprised 30 adult male Wistar rats (almost three months old) randomly distributed into the following groups; control, DZN (40 mg/kg), DZN + ALA (40 mg/kg+100 mg/kg), ALA (100 mg/kg), and sham. The rats were anesthetized after six weeks. Blood sampling was performed, and kidneys were removed for immunohistochemistry study. Diazinon reduced the distribution of fibronectin and laminin and significantly inhibited cholinesterase activity in the renal tubules. Furthermore, urea and creatinine levels were higher in diazinon than in other groups. ALA in the co-treatment group enhanced cholinesterase activity and distribution of both glycoproteins in the renal tubules. Urea and creatinine levels were meaningfully diminished in the DZN + ALA group. The nephrotoxic effect of diazinon in vivo was the reduced distribution of laminin and fibronectin, probably induced by cholinesterase activity inhibition. As an antioxidant with specific properties, ALA reduces the nephrotoxic effects of diazinon by multifarious mechanisms.

Increased iNOS and Nitrosative Stress in Dopaminergic Neurons of MDMA-Exposed Rats

Several mechanisms underlying 3,4-Methylenedioxy-N-methylamphetamine (MDMA) neurotoxicity have been proposed, including neurochemical alterations and excitotoxicity mediated by reactive oxygen species (ROS), nitric oxide (NO), and reactive nitrogen species (RNS). However, ROS, NO, and RNS sources in the brain are not fully known. We aimed to investigate possible alterations in the expression of the ROS producer NOX enzymes (NOX2, NOX1, and NOX4), NO generators (iNOS, eNOS, and nNOS), markers of oxidative (8-hydroxy-2′-deoxyguanosine, 8OHdG), and nitrosative (3-nitrotyrosine, NT) stress, as well as the colocalization between cells positive for the dopamine transporter (DT1) and cells expressing the neuronal nuclei (NeuN) marker, in the frontal cortex of rats receiving saline or MDMA, sacrificed 6 h, 16 h, or 24 h after its administration. MDMA did not affect NOX2, NOX1, and NOX4 immunoreactivity, whereas iNOS expression was enhanced. The number of NT-positive cells was increased in MDMA-exposed animals, whereas no differences were detected in 8OHdG expression among experimental groups. MDMA and NT markers colocalized with DT1 positive cells. DT1 immunostaining was found in NeuN-positive stained cells. Virtually no colocalization was observed with microglia and astrocytes. Moreover, MDMA immunostaining was not found in NOX2-positive cells. Our results suggest that iNOS-derived nitrosative stress, but not NOX enzymes, may have a crucial role in the pathogenesis of MDMA-induced neurotoxicity, highlighting the specificity of different enzymatic systems in the development of neuropathological alterations induced by the abuse of this psychoactive compound.