The Path to New Therapies for Schizophrenia and Bipolar Illness

A spatial model of autophosphorylation of CaMKII in a glutamatergic spine suggests a network-driven kinetic mechanism for bistable changes in synaptic strength

Activation of N-methyl-D-aspartate-type glutamate receptors (NMDARs) at synapses in the CNS triggers changes in synaptic strength that underlie memory formation in response to strong synaptic stimuli. The primary target of Ca2+ flowing through NMDARs is Ca2+/calmodulin-dependent protein kinase II (CaMKII) which forms dodecameric holoenzymes that are highly concentrated at the postsynaptic site. Activation of CaMKII is necessary to trigger long-term potentiation of synaptic strength (LTP), and is prolonged by autophosphorylation of subunits within the holoenzyme. Here we use MCell4, an agent-based, stochastic, modeling platform to model CaMKII holoenzymes placed within a realistic spine geometry. We show how two mechanisms of regulation of CaMKII, 'Ca2+-calmodulin-trapping (CaM-trapping)' and dephosphorylation by protein phosphatase-1 (PP1) shape the autophosphorylation response during a repeated high-frequency stimulus. Our simulation results suggest that autophosphorylation of CaMKII does not constitute a bistable switch. Instead, prolonged but temporary, autophosphorylation of CaMKII may contribute to a biochemical-network-based 'kinetic proof-reading" mechanism that controls induction of synaptic plasticity.

Advances toward precision medicine for bipolar disorder: mechanisms & molecules

Given its chronicity, contribution to disability and morbidity, and prevalence of more than 2%, the effective treatment, and prevention of bipolar disorder represents an area of significant unmet medical need. While more than half a century has passed since the introduction of lithium into widespread use at the birth of modern psychopharmacology, that medication remains a mainstay for the acute treatment and prevention of recurrent mania/hypomania and depression that characterize bipolar disorder. However, the continued limited understanding of how lithium modulates affective behavior and lack of validated cellular and animal models have resulted in obstacles to discovering more effective mood stabilizers with fewer adverse side effects. In particular, while there has been progress in developing new pharmacotherapy for mania, developing effective treatments for acute bipolar depression remain inadequate. Recent large-scale human genetic studies have confirmed the complex, polygenic nature of the risk architecture of bipolar disorder, and its overlap with other major neuropsychiatric disorders. Such discoveries have begun to shed light on the pathophysiology of bipolar disorder. Coupled with broader advances in human neurobiology, neuropharmacology, noninvasive neuromodulation, and clinical trial design, we can envision novel therapeutic strategies informed by defined molecular mechanisms and neural circuits and targeted to the root cause of the pathophysiology. Here, we review recent advances toward the goal of better treatments for bipolar disorder, and we outline major challenges for the field of translational neuroscience that necessitate continued focus on fundamental research and discovery.

Double-Dissociation Studies in Psychiatric Research: A Scoping Review

LEARNING OBJECTIVES

After participating in this activity, learners should be better able to:• Evaluate the double-dissociation approach to research in neuropsychology• Assess research aiming to provide evidence of double dissociation between neurobiological abnormalities and clinical presentations in psychiatry BACKGROUND: Psychiatric neuroscience research has grown exponentially, but it has not generated the desired breakthroughs in diagnosis, treatment development, or treatment selection. In many instances a given neurobiological abnormality is found in multiple clinical syndromes, and conversely, a clinical syndrome is associated with multiple neurobiological abnormalities. To the extent that neurobiology research is conducted to explain psychiatric manifestations, however, it should also provide insight into how certain brain abnormalities lead to one and not another specific clinical presentation-that is, "double-dissociation." We hypothesized that most psychiatric research studies are not designed to identify such double dissociations.

METHODS

We selected three leading psychiatric journals (American Journal of Psychiatry, JAMA Psychiatry, and Molecular Psychiatry) that are representative of high-quality psychiatry research and that also provided a sample size that was feasible to screen. We screened all original research manuscripts published over the course of one calendar year (2017) to identify those measuring brain function or biological parameters (which, collectively, we term neurobiological measures) in psychiatric disorders. We asked whether such biological research could provide evidence for a double dissociation of any kind.

RESULTS

We found that only 7 of 403 articles published in three psychiatry journals, constituting approximately 2% of publications, examined the dissociation of neurobiological measures relating to two psychiatric disorders or symptom clusters. Of these 7 studies, 5 used imaging as research tool; 1 used genotype array; and 1 used polymerase chain reaction (PCR). Sample sizes of the 7 studies ranged from 100 to 2876.

CONCLUSION

We report on a striking paucity of research aiming to provide evidence of double dissociation between neurobiological abnormalities and clinical presentations in psychiatry. We conclude that this paucity represents a missed opportunity for the field. Double-dissociation approaches have been used successfully in many studies in neurology and psychiatry in the past, and more widespread and explicit adoption of this design may improve the mechanistic insights obtained in psychiatry research.