Postsynaptic Spiking Homeostatically Induces Cell-Autonomous Regulation of Inhibitory Inputs via Retrograde Signaling

Abstract

Developing neural circuits face the dual challenge of growing in an activity-induced fashion and maintaining stability through homeostatic mechanisms. Compared to our understanding of homeostatic regulation of excitatory synapses, relatively little is known about the mechanism mediating homeostatic plasticity of inhibitory synapses, especially that following activity elevation. Here, we found that elevating neuronal activity in cultured hippocampal neurons for 4 h significantly increased the frequency and amplitude of mIPSCs, before detectable change at excitatory synapses. Consistently, we observed increases in presynaptic and postsynaptic proteins of GABAergic synapses, including GAD65, vGAT, and GABA A R␣1. By suppressing activity-induced increase of neuronal firing with expression of the inward rectifier potassium channel Kir2.1 in individual neurons, we showed that elevation in postsynaptic spiking activity is required for activity-dependent increase in the frequency and amplitude of mIPSCs. Importantly, directly elevating spiking in individual postsynaptic neurons, by capsaicin activation of overexpressed TRPV1 channels, was sufficient to induce increased mIPSC amplitude and frequency, mimicking the effect of elevated neuronal activity. Downregulating BDNF expression in the postsynaptic neuron or its extracellular scavenging prevented activity-induced increase in mIPSC frequency, consistent with a role of BDNF-dependent retrograde signaling in this process. Finally, elevating activity in vivo by kainate injection increased both mIPSC amplitude and frequency in CA1 pyramidal neurons. Thus, spiking-induced, cell-autonomous upregulation of GABAergic synaptic inputs, through retrograde BDNF signaling, represents an early adaptive response of neural circuits to elevated network activity.

Pathogenic Mutations in the Valosin-containing Protein/p97(VCP) N-domain Inhibit the SUMOylation of VCP and Lead to Impaired Stress Response

“…Cells were treated with sodium arsenite (S7400, Sigma), MG132 (47490, Merck), paraquat (PS366, Sigma), and tunicamycin (T7765, Sigma) as indicated. Primary cortical neuronal cultures were prepared from neocortical fragments of postnatal day 0 (P0) Sprague-Dawley rat pups as described (62). HeLa cells stably expressing TCR␣-GFP were established by transient transfection followed by G418 (800 g/ml) selection.…”

Dystroglycan mediates homeostatic synaptic plasticity at GABAergic synapses

“…Homeostatic synaptic plasticity is widely thought to be essential for brain function and involves the reciprocal regulation of glutamatergic and GABAergic synapses to stabilize neuronal activity (21). Chronic elevation of neuronal activity is associated with an increase in synaptic GABA A Rs (22,23), but the mechanistic details are incompletely understood.…”

Activity-regulated Somatostatin Expression Reduces Dendritic Spine Density and Lowers Excitatory Synaptic Transmission via Postsynaptic Somatostatin Receptor 4

“…Hippocampal Neuronal Cultures and Transfection-High density mixed neuronal-glial cultures were prepared from postnatal day 0 Sprague-Dawley rat pups as previously described (32,33) and according to procedures approved by the Institutional Animal Care and Use Committee of the Institute of Neuroscience of the Chinese Academy of Sciences (Shanghai, China). The dentate gyrus was removed during the dissection, leaving CA1 and CA3 pyramidal neurons as the main glutamatergic neuronal types in the preparation.…”

“…Immunostaining, Image Acquisition, and Analysis-Immunocytochemistry for hippocampal neuronal cultures was carried out as previously described (32). For surface GluR2 staining, GluR2 antibody (mouse, 1:200, Millipore) was added to the medium of cultured neurons for 15 min at 37°C prior to fixation.…”

“…Electrophysiological Recordings in Cultured NeuronsWhole cell patch clamp recordings were carried out at room temperature on DIV 11-13 neurons using a Multiclamp 700B amplifier (Molecular Devices) as previously described (32). The extracellular solution contained 129 mM NaCl, 5 mM KCl, 30 mM glucose, 25 mM HEPES, 2 mM CaCl 2 , 1 mM MgCl 2 (pH 7.3, 310 mOsm).…”