Environmental Enrichment and Social Isolation Mediate Neuroplasticity of Medium Spiny Neurons through the GSK3 Pathway

Abstract

Resilience and vulnerability to neuropsychiatric disorders are linked to molecular changes underlying excitability that are still poorly understood. Here, we identify glycogen-synthase kinase 3β (GSK3β) and voltage-gated Na channel Nav1.6 as regulators of neuroplasticity induced by environmentally enriched (EC) or isolated (IC) conditions-models for resilience and vulnerability. Transcriptomic studies in the nucleus accumbens from EC and IC rats predicted low levels of GSK3β and SCN8A mRNA as a protective phenotype associated with reduced excitability in medium spiny neurons (MSNs). In vivo genetic manipulations demonstrate that GSK3β and Nav1.6 are molecular determinants of MSN excitability and that silencing of GSK3β prevents maladaptive plasticity of IC MSNs. In vitro studies reveal direct interaction of GSK3β with Nav1.6 and phosphorylation at Nav1.6 by GSK3β. A GSK3β-Nav1.6 competing peptide reduces MSNs excitability in IC, but not EC rats. These results identify GSK3β regulation of Nav1.6 as a biosignature of MSNs maladaptive plasticity.

Chronic mild stress alters synaptic plasticity in the nucleus accumbens through GSK3β-dependent modulation of Kv4.2 channels

“…Electrophysiological recordings in acute slices of the NAc shell were performed with the whole-cell patchclamp technique from visually identified MSNs, which represent >95% of the neurons in this brain region. In addition to morphological criteria, MSNs were identified based on previously defined electrophysiological parameters (25,26). In some experiments, cells were filled with biocytin and morphologically reconstructed for further validation ( Fig.…”

Bidirectional Modulation of the Voltage-Gated Sodium (Nav1.6) Channel by Rationally Designed Peptidomimetics

“…The two plasmids (pET28a-FGF14; pET30a-Nav1.6) for protein expression and purification of FGF14 (accession number NP_787125; aa 64-252) and Nav1.6 C-tail (accession number #NP_001171455; aa 1763-1912) have been previously described [36,45] and were transformed into E. coli BL21 (DE3) pLys (Invitrogen). Cells were grown until OD 600 = 0.7, and the recombinant proteins were expressed after induction with 0.1 mM isopropyl thio-β-d-galacto-pyranoside (IPTG) for 24 h at 16 • C. Cells were harvested and lysed by sonication at 4 • C in lysis/binding buffer containing the following components (mM): 10 sodium phosphate (prepared from 0.5 M of Na 2 HPO 4 and NaH 2 PO 4 ), 25 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), 150 NaCl, phenyl methyl sulphonyl fluoride (PMSF) 0.1, 3-((3-cholamidopropyl) dimethylammonio)-1-propanesulfonate (CHAPS) 0.1% pH 7.0 (for FGF14), and with glycerol 10% (for Nav1.6 C-tail) pH 7.5.…”

Neurobehavioral Effects of Restricted and Unpredictable Environmental Enrichment in Rats

“…These mRNA analyses were performed in SH5, REE, and CEE rats that were not submitted to behavioral assessment. We extracted the nucleus accumbens, dorsal striatum, and hippocampus because 1) they are all involved in different phases of the motivational processes (e.g., attribution of incentive salience, the transition from motivation to action, and contextual encoding of reward cues) (Williams and Undieh, 2010;Anselme et al, 2013;Schultz, 2016); 2) they play a pivotal role on learning and memory (e.g., associative, procedural, and episodic/spatial memory) (Richard et al, 2013;Lisman et al, 2017); and 3) the EE-induced physiological and cellular effects have been well identified in those regions and especially in hippocampus (Bezard et al, 2003;Tipyasang et al, 2014;Brenes et al, 2016;Grimm et al, 2018;Scala et al, 2018;Ohline and Abraham, 2019).…”