Depression Treatment: On the Mechanism of Synaptic Depression Induced by CaMKIIN, an Endogenous Inhibitor of CaMKII.

On the Mechanism of Synaptic Depression Induced by CaMKIIN, an Endogenous Inhibitor of CaMKII.

Filed under: Depression Treatment

PLoS One. 2012; 7(11): e49293
Gouet C, Aburto B, Vergara C, Sanhueza M

Activity-dependent synaptic plasticity underlies, at least in part, learning and memory processes. NMDA receptor (NMDAR)-dependent long-term potentiation (LTP) is a major synaptic plasticity model. During LTP induction, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is activated, autophosphorylated and persistently translocated to the postsynaptic density, where it binds to the NMDAR. If any of these steps is inhibited, LTP is disrupted. The endogenous CaMKII inhibitor proteins CaMKIIN?,? are rapidly upregulated in specific brain regions after learning. We recently showed that transient application of peptides derived from CaMKIIN? (CN peptides) persistently depresses synaptic strength and reverses LTP saturation, as it allows further LTP induction in previously saturated pathways. The treatment disrupts basal CaMKII-NMDAR interaction and decreases bound CaMKII fraction in spines. To unravel CaMKIIN function and to further understand CaMKII role in synaptic strength maintenance, here we more deeply investigated the mechanism of synaptic depression induced by CN peptides (CN-depression) in rat hippocampal slices. We showed that CN-depression does not require glutamatergic synaptic activity or Ca(2+) signaling, thus discarding unspecific triggering of activity-dependent long-term depression (LTD) in slices. Moreover, occlusion experiments revealed that CN-depression and NMDAR-LTD have different expression mechanisms. We showed that CN-depression does not involve complex metabolic pathways including protein synthesis or proteasome-mediated degradation. Remarkably, CN-depression cannot be resolved in neonate rats, for which CaMKII is mostly cytosolic and virtually absent at the postsynaptic densities. Overall, our results support a direct effect of CN peptides on synaptic CaMKII-NMDAR binding and suggest that CaMKIIN?,? could be critical plasticity-related proteins that may operate as cell-wide homeostatic regulators preventing saturation of LTP mechanisms or may selectively erase LTP-induced traces in specific groups of synapses.
HubMed – depression

A Neuronal Network Model for Simulating the Effects of Repetitive Transcranial Magnetic Stimulation on Local Field Potential Power Spectra.

Filed under: Depression Treatment

PLoS One. 2012; 7(11): e49097
Bey A, Leue S, Wienbruch C

Repetitive transcranial magnetic stimulation (rTMS) holds promise as a non-invasive therapy for the treatment of neurological disorders such as depression, schizophrenia, tinnitus, and epilepsy. Complex interdependencies between stimulus duration, frequency and intensity obscure the exact effects of rTMS stimulation on neural activity in the cortex, making evaluation of and comparison between rTMS studies difficult. To explain the influence of rTMS on neural activity (e.g. in the motor cortex), we use a neuronal network model. The results demonstrate that the model adequately explains experimentally observed short term effects of rTMS on the band power in common frequency bands used in electroencephalography (EEG). We show that the equivalent local field potential (eLFP) band power depends on stimulation intensity rather than on stimulation frequency. Additionally, our model resolves contradictions in experiments.
HubMed – depression

Monoaminergic Modulation of Spinal Viscero-Sympathetic Function in the Neonatal Mouse Thoracic Spinal Cord.

Filed under: Depression Treatment

PLoS One. 2012; 7(11): e47213
Zimmerman AL, Sawchuk M, Hochman S

Descending serotonergic, noradrenergic, and dopaminergic systems project diffusely to sensory, motor and autonomic spinal cord regions. Using neonatal mice, this study examined monoaminergic modulation of visceral sensory input and sympathetic preganglionic output. Whole-cell recordings from sympathetic preganglionic neurons (SPNs) in spinal cord slice demonstrated that serotonin, noradrenaline, and dopamine modulated SPN excitability. Serotonin depolarized all, while noradrenaline and dopamine depolarized most SPNs. Serotonin and noradrenaline also increased SPN current-evoked firing frequency, while both increases and decreases were seen with dopamine. In an in vitro thoracolumbar spinal cord/sympathetic chain preparation, stimulation of splanchnic nerve visceral afferents evoked reflexes and subthreshold population synaptic potentials in thoracic ventral roots that were dose-dependently depressed by the monoamines. Visceral afferent stimulation also evoked bicuculline-sensitive dorsal root potentials thought to reflect presynaptic inhibition via primary afferent depolarization. These dorsal root potentials were likewise dose-dependently depressed by the monoamines. Concomitant monoaminergic depression of population afferent synaptic transmission recorded as dorsal horn field potentials was also seen. Collectively, serotonin, norepinephrine and dopamine were shown to exert broad and comparable modulatory regulation of viscero-sympathetic function. The general facilitation of SPN efferent excitability with simultaneous depression of visceral afferent-evoked motor output suggests that descending monoaminergic systems reconfigure spinal cord autonomic function away from visceral sensory influence. Coincident monoaminergic reductions in dorsal horn responses support a multifaceted modulatory shift in the encoding of spinal visceral afferent activity. Similar monoamine-induced changes have been observed for somatic sensorimotor function, suggesting an integrative modulatory response on spinal autonomic and somatic function.
HubMed – depression

Life-long maintenance treatment in major depression: risk vs. benefits – Guy Goodwin, MD ( University of Oxford) WA Handley Professor of Psychiatry University of Oxford Oxford, UK For more videos, go to www.gmeded.com. GME does not provide medical advice. The website and articles are intended for informational purposes only. They are not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the GME Website. If you think you may have a medical emergency, immediately call your doctor or dial 911. Global Medical Education Terms of Use http

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