Developmental regulation and lateralization of GABA receptors in the rat hippocampus

Grape seed extract protects rat offspring hippocampus from the silicon dioxide nanoparticles' neurotoxicity

Silicon dioxide nanoparticles (SiO2-NPs) can be found in many products, such as composites, paints, ceramics, consumer products, and food additives. We recently demonstrated that via breastfeeding, SiO2-NPs transfer to the offspring's brain, interfering negatively with hippocampus development. In this work, we evaluated the protective effect of grape seed extract (GSE) against the adverse effects of SiO2-NPs. After delivery, animals were administered 25 mg/kg SiO2-NPs with/without GSE (300 mg/kg) for 20 days (from 2nd to 21st days post-delivery) by gavage. SiO2-NPs increased malondialdehyde concentration and decreased antioxidant activity in the offspring's hippocampi. The mean number of dark neurons (DNs) was significantly higher in the hippocampi of the SiO2-NPs group, whereas the mean number of DCX + cells was significantly lower than in the control group. The offspring in the SiO2-NPs groups had a weak cognitive performance in adulthood. Interestingly, these adverse effects of SiO2-NPs were alleviated in the GSE-treated groups. Therefore, GSE can attenuate the damaging effects of maternal exposure to SiO2-NPs during lactation.

Hippocampal toxicity of metal base nanoparticles. Is there a relationship between nanoparticles and psychiatric disorders?

Metal base nanoparticles are widely produced all over the world and used in many fields and products such as medicine, electronics, cosmetics, paints, ceramics, toys, kitchen utensils and toothpastes. They are able to enter the body through digestive, respiratory, and alimentary systems. These nanoparticles can also cross the blood brain barrier, enter the brain and aggregate in the hippocampus. After entering the hippocampus, they induce oxidative stress, neuro-inflammation, mitochondrial dysfunction, and gene expression alteration in hippocampal cells, which finally lead to neuronal apoptosis. Metal base nanoparticles can also affect hippocampal neurogenesis and synaptic plasticity that both of them play crucial role in memory and learning. On the one hand, hippocampal cells are severely vulnerable due to their high metabolic activity, and on the other hand, metal base nanoparticles have high potential to damage hippocampus through variety of mechanisms and affect its functions. This review discusses, in detail, nanoparticles' detrimental effects on the hippocampus in cellular, molecular and functional levels to reveal that according to the present information, which types of nanoparticles have more potential to induce hippocampal toxicity and psychiatric disorders and which types should be more evaluated in the future studies.

Keeping the Balance: GABAB Receptors in the Developing Brain and Beyond

The main neurotransmitter in the brain responsible for the inhibition of neuronal activity is γ-aminobutyric acid (GABA). It plays a crucial role in circuit formation during development, both via its primary effects as a neurotransmitter and also as a trophic factor. The GABA_B receptors (GABA_BRs) are G protein-coupled metabotropic receptors; on one hand, they can influence proliferation and migration; and, on the other, they can inhibit cells by modulating the function of K⁺ and Ca²⁺ channels, doing so on a slower time scale and with a longer-lasting effect compared to ionotropic GABA_A receptors. GABA_BRs are expressed pre- and post-synaptically, at both glutamatergic and GABAergic terminals, thus being able to shape neuronal activity, plasticity, and the balance between excitatory and inhibitory synaptic transmission in response to varying levels of extracellular GABA concentration. Furthermore, given their subunit composition and their ability to form complexes with several associated proteins, GABA_BRs display heterogeneity with regard to their function, which makes them a promising target for pharmacological interventions. This review will describe (i) the latest results concerning GABA_BRs/GABA_BR-complex structures, their function, and the developmental time course of their appearance and functional integration in the brain, (ii) their involvement in manifestation of various pathophysiological conditions, and (iii) the current status of preclinical and clinical studies involving GABA_BR-targeting drugs.

Paradoxical Enhancement of Spatial Learning Induced by Right Hippocampal Lesion in Rats

The left–right hemispheric differences in some brain functions are well known in humans. Among them, savant syndrome has unique features, such as exceptional abilities in vision, memory, computation, and music, despite brain abnormalities. In cases of acquired savant and transient savant, brain damage or inhibition is often seen in the left hemisphere, suggesting a link between left hemispheric dysfunction and these talents. On the other hand, some functional left–right differences have been reported in rodent brains, and therefore, unilateral damage in rodents may also result in savant-like enhancements. In the present study, we examined the effects of hippocampal damage on spatial learning in rats with left, right, or bilateral hippocampal lesion. The results showed that learning performance was impaired in the bilateral lesion group, and there was no significant difference in the left lesion group, while performance was enhanced in the right lesion group. These results suggest that damage to the right hippocampus in rats may lead to savant-like enhancement in learning and memory. The construction of the savant model through these results will contribute to the neuroscientific elucidation of the paradoxical phenomenon observed in savants, that some abilities are enhanced despite their brain dysfunction.

Developmental regulation and lateralization of N-methyl-d-aspartate (NMDA) receptors in the rat hippocampus

N-methyl-d-aspartate receptors (NMDARs) are expressed abundantly in the brain and play a crucial role in the regulation of central nervous system (CNS) development, learning, and memory. During early neuronal development, NMDARs modulate neurogenesis, neuronal differentiation and migration, and synaptogenesis. The present study aimed to examine the developmental expression of NMDARs subunits, NR1 and NR2B, in the developing hippocampus of neonatal rats during the first two postnatal weeks. Fifty-four male offspring were randomly divided into three age groups, postnatal days (P) 0, 7, and 14. Real-time-PCR, western blotting, and immunohistochemistry (IHC) analyses were employed to examine and compare the hippocampal expression of the NMDA receptor subunits. The highest mRNA expression of NR1 and NR2B subunits was observed at P7, regardless of its laterality. The mRNA expression of both subunits in the right hippocampus was significantly higher than that of the left one at P0 and P7. Similarly, the highest protein level expression of NR1 and NR2B subunits was also observed at P7 in both sides hippocampi. Although the protein expression of NR1 was significantly higher on the right side in all studied days, the NR2B was significantly higher in the right hippocampus only at P7. The analysis of optical density (OD) has shown a marked increase in the distribution pattern of the NR1 and NR2B subunits at P7 in all hippocampal subregions. In conclusion, there is a marked right-left asymmetry in the expression of NR1 and NR2B subunits in the developing rat hippocampus, which might be considered as a probable mechanism for the lateral differences in the structure and function of the hippocampus in rats.

Cell and molecular toxicity of lanthanum nanoparticles: are there possible risks to humans?

Lanthanum nanoparticles are widely used in industry, agriculture, and biomedicine. Over 900 kg of lanthanum is annually released into the environment only in Europe, 50 times higher than the metals, mercury, and cadmium's environmental spread. Human health risk associated with long-term exposure to the abundant lanthanum nanoparticles is a concerning environmental issue. Due to lanthanum's ability to disrupt the main biological barriers and interrupt various cells' hemostasis, they seem to cause severe disruptions to various tissues. This review opens a new perspective regarding the cellular and molecular interaction of nanosized and ionic lanthanum with the possible toxicity on the nervous system and other tissues that would show lanthanum nanoparticles' potential danger to follow in toxicological science.

Hippocampal asymmetry and regional dispersal of nAChRs alpha4 and alpha7 subtypes in the adult rat

To better comprehend the relationship between left/right (L/R) differences and hippocampus functions is necessary knowledge of lateral asymmetry and regional distribution. This research was design to examine hippocampal L/R asymmetry and regional distribution profile of the alpha7 and alpha4 subtypes of nicotinic acetylcholine receptors (nAChRs) in the adult rat. 10-12-week-old twenty-four male wistar rats were randomly selected. After removing the brains, immunohistochemistry, real-time PCR, and western blot methods were applied to distinguish the presence of the receptors in the hippocampus. Outcomes stated that the mentioned receptors expression profile was spatial-dependent. As, the hippocampal dispersal of alpha7 and alpha4 subtypes in the left hippocampus (LH) was remarkably maximum compare with the right hippocampus (RH) (p = 0.001, p = 0.005 respectively). Furthermore, the alpha7 optical density (OD) was not significantly different in the diverse regions in hippocampus of adult rat (p = 0.057), while the maximum OD of the alpha4 was detected in the hippocampal dentate gyrus and CA3 regions of LH (p = 0.007, p = 0.009 respectively) and the minimum OD was in the CA1 of the RH (p = 0.019). In real time PCR evaluation, there is a significantly higher expression of alpha7 and alpha4 in LH compared to RH (p = 0.043, p = 0.049 respectively), also, for western blot (p = 0.042, p = 0.030 respectively). According to present data, the alpha7 and alpha4 nAChR subtypes expression profile demonstrated lateral asymmetry, the uniform regional dispersal for alpha7 and different regional dispersal for alpha4 in the adult rat hippocampus.

Grape seed extract effects on hippocampal neurogenesis, synaptogenesis and dark neurons production in old mice. Can this extract improve learning and memory in aged animals?

BACKGROUND

During the elderly, hippocampal neurogenesis and synaptogenesis reduce and dark neurons (DNs) increase, leading to cognitive impairment. It is believed that natural products can protect the neural cells and system by protecting from damages or promoting regeneration. Therefore, the effects of grape seed extract (GSE) on the hippocampus of aged mice were investigated in this study.

METHODS

twelve old mice were divided into two groups of control and GSE. Animals in the GSE group received 300 mg/kg of GSE for eight weeks via gavage. At the end of treatment, cognition performance was evaluated by Morris water maze (MWM) and passive avoidance tests. Hippocampal neurogenesis, synaptogenesis and DNs production were evaluated with immunohistochemistry and histological evaluations on 5-micron coronal tissue sections.

RESULTS

The hippocampal mean number of double cortin positive cells (DCX⁺) per unit area, as well as synaptophysin expression in the GSE group, were significantly higher than the control group (p < 0.01). The frequency of DNs in the GSE group was lower than the control group (p < 0.05). Behavioral tests showed that GSE improves memory and learning performance.

CONCLUSION

Consuming GSE in the elderly can potentially alleviate the age-related reduction of hippocampal neurogenesis and synaptogenesis. It is also able to decrease hippocampal DNs production and increase memory and learning.

The protective effect of alpha-lipoic acid on the expression of collagen IV, renal function, and oxidative stress induced by diazinon in the renal parenchyma of rat

Diazinon (DZN) is an organophosphate pesticide that is commonly used in agriculture worldwide, including in Iran, and unfortunately, it leads to a variety of negative effects on the environment, animals, and humans. Alpha-lipoic acid (ALA) is an antioxidant agent that acts via scavenging of oxygen-free radicals. Collagen IV is a component of the main base membrane structure and DZN may also affect the expression of this key protein. The aim of this study was to evaluate antioxidant properties of ALA on the expression of collagen IV, renal function, and oxidative stress induced by DZN in renal tissue. In this experimental study, 30 adult male Wistar rats were randomly divided into five groups (n = 6) including: the control group, DZN (40 mg/kg) group, ALA (100 mg/kg) group, ALA (100 mg/kg) + DZN (40 mg/kg) group, and sham group. On day 0 and after 6 weeks, the urine and blood samples were collected to measure glomerular filtration rate (GFR). After 6 weeks, the rats were anesthetized and the left kidney was used for immunohistochemistry study and the right kidney was used to evaluate the oxidative stress parameters. The results have shown that ALA significantly improved the biochemical parameters including superoxide dismutase, glutathione peroxidase, glutathione S-transferase, glutathione reductase, and GFR. In addition, ALA significantly prevented the expression of collagen IV that was changed by DZN administration in rats. We concluded that when exposed to DZN, depletion of antioxidant enzymes is accompanied by the induction of oxidative stress that might be beneficial in monitoring DZN toxicity and alpha-lipoic acid, as an antioxidant can overcome the toxicity induced by DZN in the kidney.