IS OXYTOCIN RELEVANT FOR THE AFFECTIVE DISORDERS?

Oxytocin: Narrative Expert Review of Current Perspectives on the Relationship with Other Neurotransmitters and the Impact on the Main Psychiatric Disorders

Is a cyclic neuropeptide produced primarily in the hypothalamus and plays an important neuromodulatory role for other neurotransmitter systems, with an impact on behavior, response to danger, stress, and complex social interactions, such as pair bonding and child care. This narrative expert review examines the literature on oxytocin as a brain hormone. We focused on oxytocin structure, distribution, genetics, and the oxytocin receptor system, as well as the relationship of oxytocin with other neurotransmitters and the resulting impacts on the main psychiatric disorders. Oxytocin levels have been correlated over time with mental illness, with numerous studies focusing on oxytocin and the pathophysiology of the main psychiatric disorders, such as autism, schizophrenia, personality disorders, mood, and eating disorders. We highlight the role oxytocin plays in improving symptoms such as anxiety, depression, and social behavior, as the literature suggests. Risk factors and causes for psychiatric disorders range from genetic to environmental and social factors. Oxytocin could impact the latter, being linked with other neurotransmitter systems that are responsible for integrating different situations during the development phases of individuals. Also, these systems have an important role in how the body responds to stressors or bonding with others, helping with the creation of social support groups that could speed up recovery in many situations. Oxytocin has the potential to become a key therapeutic agent for future treatment and prevention strategies concerning the main psychiatric disorders.

Intranasal Oxytocin Attenuates Cognitive Impairment, β-Amyloid Burden and Tau Deposition in Female Rats with Alzheimer's Disease: Interplay of ERK1/2/GSK3β/Caspase-3

Oxytocin is a neuropeptide hormone that plays an important role in social bonding and behavior. Recent studies indicate that oxytocin could be involved in the regulation of neurological disorders. However, its role in modulating cognition in Alzheimer’s disease (AD) has never been explored. Hence, the present study aims to investigate the potential of chronic intranasal oxytocin in halting memory impairment & AD pathology in aluminum chloride-induced AD in female rats. Morris water maze was used to assess cognitive dysfunction in two-time points throughout the treatment period. In addition, neuroprotective effects of oxytocin were examined by assessing hippocampal acetylcholinesterase activity, β-amyloid 1–42 protein, and Tau levels. In addition, ERK1/2, GSK3β, and caspase-3 levels were assessed as chief neurobiochemical mediators in AD. Hippocampi histopathological changes were also evaluated. These findings were compared to the standard drug galantamine alone and combined with oxytocin. Results showed that oxytocin restored cognitive functions and improved animals’ behavior in the Morris test. This was accompanied by a significant decline in acetylcholinesterase activity, 1–42 β-amyloid and Tau proteins levels. Hippocampal ERK1/2 and GSK3β were also reduced, exceeding galantamine effects, thus attenuating AD pathological hallmarks formation. Determination of caspase-3 revealed low cytoplasmic positivity, indicating the ceasing of neuronal death. Histopathological examination confirmed these findings, showing restored hippocampal cells structure. Combined galantamine and oxytocin treatment showed even better biochemical and histopathological profiles. It can be thus concluded that oxytocin possesses promising neuroprotective potential in AD mediated via restoring cognition and suppressing β-amyloid, Tau accumulation, and neuronal death.

Cortisol and Oxytocin Could Predict Covert Aggression in Some Psychotic Patients

Background: The covert or indirect type of aggression has a risk of converting in violent acts and, considering that, it is very important to identify it in order to apply effective preventive measures. In cases of psychotic patients, the risk of becoming violent is harder to predict, as even neuter stimuli may be perceived as threat and trigger aggression. Treating all the psychiatric patients as potential aggressive subjects is not the best preventive measure as only a few of them are aggressive and this measure may further enhance the stigma on mentally ill patients. There is a current need for better understanding of covert aggression and to find objective measures, such as biological markers, that could be indicative of potential violent behavior. In this work, we try to investigate the role of cortisol and oxytocin as potential biomarkers of aggression in patients with psychosis. Material and Methods: We analyzed the level of peripheral oxytocin (pg/mL) and cortisol level (ng/mL) in 28 psychotic patients (they were not on psychotropic treatment at the moment of admission and those with substance abuse or personality disorder were excluded from the study) and correlated it with the intensity of aggression reported by the patient (overt and covert type) using the Overt Covert Aggression Inventory and the level of observed aggression of the patient in the past 7 days (rated by the health care provider) using the Modified Overt Aggression Scale. Results: We found that psychotic patients with a higher level of covert aggression had a lower level of cortisol (61.05 ± 8.04 ng/mL vs. 216.33 ± 12.6.9 ng/mL, p ˂ 0.01) and a higher level of oxytocin (102.87 ± 39.26 vs. 70.01 ± 25.07, p = 0.01) when compared with patients with a lower level of covert aggression. Furthermore, we observed significant negative correlation between cortisol and covert aggression (r = −0.676, p < 0.001) and between oxytocin and covert type of aggression (r = 0.382, p = 0.04). Moreover, we found that a lower level of cortisol together with a higher level of oxytocin are significant predictors of a style of internalized manifestation of aggression, with the predictive model explaining 55% of the variant of the internalized manifestation of aggression (F (2.25) = 17.6, p < 0.001, β = 0.35, R² = 55.2). We did not find significant correlations between cortisol and overt aggression, and neither between oxytocin and overt aggression. Positive correlations were also found between the overt type of self-reported aggression and overt aggression reported by the rater (r = 0.459, p = 0.01). Conclusions: The importance of a predictive model in understanding covert aggression is imperative and the results of our study show that oxytocin and cortisol warrant to be further investigated in establishing a definitive predictive model for covert aggression.

Oxytocin Alleviates MPTP-Induced Neurotoxicity in Mice by Targeting MicroRNA-26a/Death-Associated Protein Kinase 1 Pathway

Neurotoxicity is one of the major pathological changes in multiple neurological disorders, including Alzheimer's disease (AD) and Parkinson's disease (PD), the second popular neurodegenerative disease in aged people. It is known that the AD and PD share the similar neuropathological hallmarks, such as the oxidative stress, loss of specific neurons, and aggregation of specific proteins. However, there are no effective therapeutic drugs for both AD and PD yet. Oxytocin (OXT) is a small peptide with 9 amino acids that is neuroprotective to many neurological disorders. Whether OXT administration confers neuroprotection to 1-methyl-4-phenyl-1, 2, 3, 6- tetrahydropyridine (MPTP)-induced neurotoxicity in mice are still not known. In this study, we first found that the OXT levels are decreased in MPTP mice. Supplementation with OXT effectively rescues the locomotor disabilities and anxiety-like behaviors in MPTP mice. OXT also alleviates the hyperphosphorylation of α-synuclein at S129 site and the loss of dopaminergic neurons in the substantia nigra pars compacta, as well as the oxidative stress in the MPTP mice, and alleviates both oxidative stress and cell cytotoxicity in vitro. Furthermore, we found that OXT could inhibit the miR-26a/DAPK1 signal pathway in MPTP mice. In summary, our study demonstrates protective effects of OXT in MPTP mice and that miR-26a/DAPK1 signaling pathway may play an important role in mediating the protection of OXT.

PLASMATIC LEVELS OF NEUROPEPTIDES, INCLUDING OXYTOCIN, IN CHILDREN WITH AUTISM SPECTRUM DISORDER, CORRELATE WITH THE DISORDER SEVERITY

Context

Oxytocin has been investigated as a potential medication for psychiatric disorders.

Objective and design

This study prospectively investigates correlations between oxytocin and other neuropeptides plasma levels in patients with autism spectrum disorders (ASD) according to severity and treatment, as compared to controls.

Subjects and methods

Thirty-one children (6 neurotypical as control) participated in this study. The patients were classified into mildly and severely-affected, according to Autism Diagnostic Observation Schedule (ADOS) scores. Oxytocin, orexin A and B, α-MSH, β-endorphins, neurotensin and substance P were investigated using a quantitative multiplex assay or a competitive-ELISA method.

Results

Plasma oxytocin levels differed between the groups (F (2, 24) =6.48, p=0.006, η2=0.35, observed power=86%): patients with the mild ASD had higher values of plasma oxytocin than those with the severe form (average difference=74.56±20.74pg/mL, p=0.004).

Conclusions

These results show a negative correlation between plasma levels of oxytocin and the severity of ASD and support the involvement of oxytocinergic mechanisms in ASD.