Effect of chronic treatment with haloperidol on vasopressin release and behavioral changes by osmotic stimulation of the supraoptic nucleus

Hyponatremia Following Antipsychotic Treatment: In Silico Pharmacodynamics Analysis of Spontaneous Reports From the US Food and Drug Administration Adverse Event Reporting System Database and an Updated Systematic Review

BACKGROUND

Hyponatremia associated with antipsychotic drugs is a rare but potentially life-threatening adverse drug reaction; the underlying pharmacological mechanism has not yet been explained.

METHODS

We investigated the relationship between pharmacological targets of antipsychotic drugs and the occurrence of hyponatremia by conducting a nested case-control study using the Food and Drug Administration Adverse Event Reporting System database. Multiple logistic regression was used to determine the associations between antipsychotics receptor occupancy and hyponatremia. We also performed a systematic review of clinical studies on this association.

RESULTS

Of 139 816 reports involving at least 1 antipsychotic, 1.1% reported hyponatremia. Olanzapine was the most frequently suspected drug (27%). A significant positive association was found between dopamine D3, D4, and hyponatremia, while adrenergic α 1, serotonin 5-HT1A, and 5-HT2A receptor occupancies were negatively associated. A multivariable stepwise regression model showed that dopamine D3 (adj. odds ratio = 1.21; 95% CI = 1.09-1.34; P < .05) predicted the risk for hyponatremia (P < .05), while serotonin 5-HT2A occupancy (Adj. odds ratio = 0.78; 95% CI = 0.68-0.90; P < .01) exhibited a protective effect against hyponatremia. Among the 11 studies included in the systematic review, incidence rates of hyponatremia diverged between 0.003% and 86%, whereas the odds of developing hyponatremia from effect studies ranged between 0.83 and 3.47.

CONCLUSIONS

Antipsychotic drugs having a combined modest occupancy for D3 and 5-HT2A receptors and higher levels of D3 receptor occupancy correspond to different degrees of risk for hyponatremia. Based on the few, relatively large-scale available studies, atypical antipsychotics have a more attenuated risk profile for hyponatremia.

A translational approach for NMDA receptor profiling as a vulnerability biomarker for depression and schizophrenia

NEW FINDINGS

What is the central question of this study? Can the change in plasma arginine vasopressin concentration (P_[AVP] ) in response to osmotic stimulation (P_Osm ) serve as a biomarker for NMDA receptor signalling in schizophrenia and depression and thereby distinguish between these mental illnesses? What is the main finding and its importance? In response to hyperosmotic challenge, depressed subjects showed increased P_[AVP] response compared with healthy control and schizophrenic subjects. However, schizophrenic subjects were not different from healthy control subjects in this small sample. The 'P_[AVP] response to P_Osm ' is a suitable biomarker to distinguish depressed versus schizophrenic patients when used with psychiatric screening. This is the first objective physiological measure for schizophrenia or depression. Altered NMDA receptor activity and glutamate signalling might underlie the pathogenesis of both schizophrenia and depression in subgroups of patients. In schizophrenia, pharmacological modelling, post-mortem and imaging data suggest reduced NMDA signalling. In contrast, recent clinical trials demonstrating the efficacy of the NMDA antagonist ketamine in severely depressed patients suggest increased NMDA receptor signalling. We conducted a proof-of-concept study to assess whether there is any in vivo evidence for an inverse association in depression and schizophrenia with respect to the NMDA receptor function. For this purpose, we used a translational approach, based on findings from animal studies that NMDA receptor is a key mediator of arginine vasopressin (AVP) release into the bloodstream. Using hypertonic saline to increase plasma osmolality (P_Osm ) and thereby induce AVP release, as done in animal studies, we found that in depressed patients the NMDA receptor-mediated AVP release induced by hypertonic saline infusion was significantly increased [0.24 (0.15) pg ml^-1  mosmol^-1 , P < 0.05] compared with schizophrenia patients [0.07 (0.07) pg ml^-1  mosmol^-1 ]. Slopes for healthy control subjects were 0.11 (0.09) pg ml^-1  mosmol^-1 which was less than the depressed group. These findings are consistent with implicated NMDA receptor-related abnormalities in depression and schizophrenia in subgroups of patients and provide the first in vivo evidence of this dichotomy.

Primary cerebral and cerebellar astrocytes display differential sensitivity to extracellular sodium with significant effects on apoptosis

Central pontine myelinolysis is one of the idiopathic or iatrogenic brain dysfunction, and the most common cause is excessively rapid correction of chronic hyponatraemia. While myelin disruption is the main pathology, as the diagnostic name indicates, a previous study has reported that astrocyte death precedes the destruction of the myelin sheath after the rapid correction of chronic low Na(+) levels, and interestingly, certain brain regions (cerebral cortex, hippocampus, etc.) are specifically damaged but not cerebellum. Here, using primary astrocyte cultures derived from rat cerebral cortex and cerebellum, we examined how extracellular Na(+) alterations affect astrocyte death and whether the response is different between the two populations of astrocytes. Twice the amount of extracellular [Na(+) ] and voltage-gated Na(+) channel opening induced substantial apoptosis in both populations of astrocytes, while, in contrast, one half [Na(+) ] prevented apoptosis in cerebellar astrocytes, in which the Na(+) -Ca(2+) exchanger, NCX2, was highly expressed but not in cerebral astrocytes. Strikingly, the rapid correction of chronic one half [Na(+) ] exposure significantly increased apoptosis in cerebellar astrocytes but not in cerebral astrocytes. These results indicate that extracellular [Na(+) ] affects astrocyte apoptosis, and the response to alterations in [Na(+) ] is dependent on the brain region from which the astrocyte is derived.

Atypical antipsychotics and polydipsia: a cause or a treatment?

Primary polydipsia (PP) is a frequent complication that affects many chronic schizophrenic inpatients. Due to possible lethal consequences, for example, hyponatremia, coma and death, it's fundamental for the physician achieving early diagnosis and treating this condition. The first step is identifying polydipsia by clinical, biochemical and pharmacological means. Nowadays, the pathophysiology of PP remains unclear, and this limits the possibility of detecting an appropriate drug treatment. Typical antipsychotics have been associated to a worsening of polydipsic behavior, while more recently atypical antipsychotics have been reported as being useful. However results are still mixed and controversial. It appears that risperidone and olanzapine are not clearly effective; clozapine may improve symptoms, although it is difficult to manage from a therapeutic point of view; quetiapine has been poorly studied so far, nonetheless it has given interesting results. Through a case study analysis, this report presents a brief, yet selective, overview of the current state of psychopharmacology in the treatment of PP with atypical antipsychotics in schizophrenia.