Aberrant regulation of oxytocin signaling is associated with the etiology of neurodevelopmental disorders. Synaptic dysfunctions in neurodevelopmental disorders are becoming increasingly known, and their pathogenic mechanisms could be a target of potential therapeutic intervention. Therefore, it is important to pay attention to the role of oxytocin and its receptor in synapse structure, function, and neuron connectivity. An early alteration in oxytocin signaling may disturb neuronal maturation and may have short-term and long-term pathological consequences. At the molecular level, neurodevelopmental disorders include alterations in cytoskeletal rearrangement and neuritogenesis resulting in a diversity of synaptopathies. The presence of oxytocin receptors in the presynaptic and postsynaptic membranes and the direct effects of oxytocin on neuronal excitability by regulating the activity of ion channels in the cell membrane implicate that alterations in oxytocin signaling could be involved in synaptopathies. The ability of oxytocin to modulate neurogenesis, synaptic plasticity, and certain parameters of cytoskeletal arrangement is discussed in the present review.
ObjectiveOxytocin (OT) has been implicated to play an important role in autism spectrum disorders (ASD) etiology. We aimed to find out the differences in plasma OT levels between children with autism and healthy children, the associations of OT levels with particular autism symptoms and the associations of particular parental autistic traits with their ASD children OT levels.MethodsWe included 19 boys with autism and 44 healthy age-matched boys. OT levels were analyzed by ELISA method. Children with autism were scored by Childhood Autism Rating Scale and Autism Diagnostic Interview (ADI), adjusted research version. Autism Spectrum Quotient (AQ), Systemizing Quotient (SQ) and Empathizing Quotient were completed by parents of children with autism.ResultsChildren with autism had significantly lower plasma OT levels than controls. OT levels positively correlated with ADI Reciprocal Interaction and Communication scores. AQ and SQ of fathers positively correlated with children plasma OT level.ConclusionOur results support the hypothesis of OT deficiency in autism. The "paradoxical" associations of OT levels and social skills in children with autism indicate disturbances at various levels of OT system. We first reported associations of OT levels in children with autism and behavioral measures in fathers indicating that OT abnormalities stay between parental autistic traits and autism symptoms in their children.
It is known that the development and plasticity of the neuroendocrine system can be affected by many factors, and that adverse events during the prenatal period can result in long-lasting changes in adulthood. This study was aimed at evaluating the possible consequences for offspring from chronic inflammation during pregnancy. Chronic inflammation was simulated by treatment with increasing doses of lipopolysaccharide (LPS) to dams on days 15 through 19 of pregnancy. Attempts were made to prevent possible negative alterations by keeping animals in an enriched environment (EE). Maternal exposure to LPS resulted in a significant reduction of body weight of male offspring during the weaning period. This difference remained until the age of 63 days in controls (C), but not in animals reared in EE. The content of dopamine in the nucleus accumbens was found to be lower in prenatally stressed (PS) adult males. Furthermore, prenatal exposure to maternal immune challenge was associated with lower locomotor activity in elevated plus maze and increased number of skips in the beam-walking test, as observed in female offspring. No differences in ACTH and corticosterone concentrations with regard to prenatal treatment were found; however, both groups kept in EE showed increased levels of corticosterone as well as enlarged adrenal glands. Thus, immune activation during pregnancy may induce long-term changes in brain catecholamines and behavior, but it is not harmful to basal hormone secretion in the offspring.
Autism spectrum disorder is a heterogeneous disease, and numerous alterations of gene expression come into play to attempt to explain potential molecular and pathophysiological causes. Abnormalities of brain development and connectivity associated with alterations in cytoskeletal rearrangement, neuritogenesis and elongation of axons and dendrites might represent or contribute to the structural basis of autism pathology. Slit/Robo signaling regulates cytoskeletal remodeling related to axonal and dendritic branching. Components of its signaling pathway (ABL and Cdc42) are suspected to be molecular bases of alterations of normal development. The present review describes the most important mechanisms underlying neuritogenesis, axon pathfinding and the role of GTPases in neurite outgrowth, with special emphasis on alterations associated with autism spectrum disorders. On the basis of analysis of publicly available microarray data, potential biomarkers of autism are discussed.
Brain oxytocin regulates a variety of social and affiliative behaviors and affects also learning and memory. However, mechanisms of its action at the level of neuronal circuits are not fully understood. The present study tests the hypothesis that molecular factors required for memory formation and synaptic plasticity, including brain-derived neurotrophic factor, neural growth factor, nestin, microtubule-associated protein 2 (MAP2), and synapsin I, are enhanced by central administration of oxytocin. We also investigated whether oxytocin enhances object recognition and acts as anxiolytic agent. Therefore, male Wistar rats were infused continuously with oxytocin (20 ng/µl) via an osmotic minipump into the lateral cerebral ventricle for 7 days; controls were infused with vehicle. The object recognition test, open field test, and elevated plus maze test were performed on the sixth, seventh, and eighth days from starting the infusion. No significant effects of oxytocin on anxious-like behavior were observed. The object recognition test showed that oxytocin-treated rats significantly preferred unknown objects. Oxytocin treatment significantly increased gene expression and protein levels of neurotrophins, MAP2, and synapsin I in the hippocampus. No changes were observed in nestin expression. Our results provide the first direct evidence implicating oxytocin as a regulator of brain plasticity at the level of changes of neuronal growth factors, cytoskeletal proteins, and behavior. The data support assumption that oxytocin is important for short-term hippocampus-dependent memory.
The aim of this study was to investigate the impact of chronic treatment with eplerenone, a mineralocorticoid receptor antagonist and clinically used antihypertensive drug, on animal correlates of mood disorders, namely anxiety-like behaviour, stress hormones release and brain plasticity. Male rats (n = 40) were injected subcutaneously twice daily with eplerenone (50 mg/kg body weight) or vehicle for 11 days. Open-field and elevated plus-maze tests were used as both anxiety-related paradigms and stress stimuli to evaluate hormone responses. Eplerenone-treated rats showed reduced anxiety-like behaviour manifested by both conventional and ethological parameters related to exploration and risk assessment behaviour in the elevated plus-maze test and partially in the open-field test. Eplerenone treatment resulted in an elevation of plasma aldosterone and oxytocin levels. Chronic treatment with eplerenone prevented the stress-induced rise in plasma corticosterone levels and vasopressin concentrations in the posterior pituitary. Eplerenone treatment failed to induce substantial changes in hippocampal brain derived neurotrophic factor protein concentrations. In conclusions, chronic treatment with eplerenone (1) exerts anxiolytic effects and (2) influences corticosterone, oxytocin and vasopressin concentrations in a manner consistent with the anxiolytic outcome.
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