Rana, S;Zhan, W;Sieck, G;Mantilla, C;
| DOI: 10.1016/j.expneurol.2022.114030
Upper cervical spinal cord injuries (SCI) disrupt descending inputs to phrenic motor neurons (PhMNs), impairing respiratory function. Unilateral spinal hemisection at C2 (C2SH) results in loss of ipsilateral rhythmic diaphragm muscle (DIAm) EMG activity associated with lower force behaviors accomplished by recruitment of smaller PhMNs that recovers over time in rats. Activity during higher force, non-ventilatory behaviors that recruit larger PhMNs is minimally impaired following C2SH. We previously showed neuroplasticity in glutamatergic receptor expression in PhMN post-C2SH with changes in NMDA receptor expression reflecting functional recovery. We hypothesize that C2SH-induced changes in glutamatergic receptor (AMPA and NMDA) mRNA expression in PhMNs vary with motor neuron size, with more pronounced changes in smaller PhMNs. Retrogradely-labelled PhMNs were classified in tertiles according to somal surface area and mRNA expression was measured using single-cell, multiplex fluorescence in situ hybridization. Ipsilateral to C2SH, a pronounced reduction in NMDA mRNA expression in PhMNs was evident at 3 days post-injury with similar impact on PhMNs in the lower size tertile (~68% reduction) and upper tertile (~60%); by 21DSH, there was near complete restoration of NMDA receptor mRNA expression across all PhMNs. There were no changes in NMDA mRNA expression contralateral to C2SH. There were no changes in AMPA mRNA expression at PhMNs on either side of the spinal cord or at any time-point post-C2SH. In summary, following C2SH there is ipsilateral reduction in PhMN NMDA mRNA expression at 3DSH that is not limited to smaller PhMN recruited in the generation of lower force ventilatory behaviors. The recovery of NMDA mRNA expression by 21DSH is consistent with evidence of spontaneous recovery of ipsilateral DIAm activity at this timepoint. These findings suggest a possible role for NMDA receptor mediated glutamatergic signaling in mechanisms supporting postsynaptic neuroplasticity at the PhMN pool and recovery of DIAm activity after cervical SCI.
Neuroscience. 2018 Dec 26.
Manohar S, Ramchander PV, Salvi R, Seigel GM.
PMID: 30593923 | DOI: 10.1016/j.neuroscience.2018.12.023
The cochlear nucleus, located in the brainstem, receives its afferent auditory input exclusively from the auditory nerve fibers of the ipsilateral cochlea. Noise-induced neurodegenerative changes occurring in the auditory nerve stimulate a cascade of neuroplastic changes in the cochlear nucleus resulting in major changes in synaptic structure and function. To identify some of the key molecular mechanisms mediating this synaptic reorganization, we unilaterally exposed rats to a high intensity noise that caused significant hearing loss and then measured the resulting changes in a synaptic plasticity gene array targeting neurogenesis and synaptic reorganization. We compared the gene expression patterns in the dorsal cochlear nucleus (DCN) and ventral cochlear nucleus (VCN) on the noise-exposed side versus the unexposed side using a PCR gene array at 2 d (early) and 28 d (late) post-exposure. We discovered a number of differentially-expressed genes, particularly those related to synaptogenesis and regeneration. Significant gene expression changes occurred more frequently in the VCN than the DCN and more changes were seen at 28 d versus 2 d post-exposure. We confirmed the PCR findings by in situ hybridization for Brain-derived neurotrophic factor (Bdnf), Homer-1, as well as the glutamate NMDA receptor Grin1, all involved in neurogenesis and plasticity. These results suggest that Bdnf, Homer-1 and Grin1 play important roles in synaptic remodeling and homeostasis in the cochlear nucleus following severe noise-induced afferent degeneration.
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology
McNulty, CJ;Fallon, IP;Amat, J;Sanchez, RJ;Leslie, NR;Root, DH;Maier, SF;Baratta, MV;
PMID: 36076018 | DOI: 10.1038/s41386-022-01443-w
Stress-linked disorders are more prevalent in women than in men and differ in their clinical presentation. Thus, investigating sex differences in factors that promote susceptibility or resilience to stress outcomes, and the circuit elements that mediate their effects, is important. In male rats, instrumental control over stressors engages a corticostriatal system involving the prelimbic cortex (PL) and dorsomedial striatum (DMS) that prevent many of the sequelae of stress exposure. Interestingly, control does not buffer against stress outcomes in females, and here, we provide evidence that the instrumental controlling response in females is supported instead by the dorsolateral striatum (DLS). Additionally, we used in vivo microdialysis, fluorescent in situ hybridization, and receptor subtype pharmacology to examine the contribution of prefrontal dopamine (DA) to the differential impact of behavioral control. Although both sexes preferentially expressed D1 receptor mRNA in PL GABAergic neurons, there were robust sex differences in the dynamic properties of prefrontal DA during controllable stress. Behavioral control potently attenuated stress-induced DA efflux in males, but not females, who showed a sustained DA increase throughout the entire stress session. Importantly, PL D1 receptor blockade (SCH 23390) shifted the proportion of striatal activity from the DLS to the DMS in females and produced the protective effects of behavioral control. These findings suggest a sex-selective mechanism in which elevated DA in the PL biases instrumental responding towards prefrontal-independent striatal circuitry, thereby eliminating the protective impact of coping with stress.
Widmer, FC;O'Toole, SM;Keller, GB;
PMID: 35170429 | DOI: 10.7554/eLife.71476
The experience of coupling between motor output and visual feedback is necessary for the development of visuomotor skills and shapes visuomotor integration in visual cortex. Whether these experience-dependent changes of responses in V1 depend on modifications of the local circuit or are the consequence of circuit changes outside of V1 remains unclear. Here, we probed the role of N-methyl-d-aspartate (NMDA) receptor-dependent signaling, which is known to be involved in neuronal plasticity, in mouse primary visual cortex (V1) during visuomotor development. We used a local knockout of NMDA receptors and a photoactivatable inhibition of CaMKII in V1 during the first visual experience to probe for changes in neuronal activity in V1 as well as the influence on performance in a visuomotor task. We found that a knockout of NMDA receptors before, but not after, first visuomotor experience reduced responses to unpredictable stimuli, diminished the suppression of predictable feedback in V1, and impaired visuomotor skill learning later in life. Our results demonstrate that NMDA receptor-dependent signaling in V1 is critical during the first visuomotor experience for shaping visuomotor integration and enabling visuomotor skill learning.
Lysko, DE;Talbot, WS;
PMID: 36384112 | DOI: 10.1016/j.celrep.2022.111669
The signaling mechanisms neurons use to modulate myelination of circuits in the central nervous system (CNS) are only partly understood. Through analysis of isoform-specific neuregulin1 (nrg1) mutants in zebrafish, we demonstrate that nrg1 type II is an important regulator of myelination of two classes of spinal cord interneurons. Surprisingly, nrg1 type II expression is prominent in unmyelinated Rohon-Beard sensory neurons, whereas myelination of neighboring interneurons is reduced in nrg1 type II mutants. Cell-type-specific loss-of-function studies indicate that nrg1 type II is required in Rohon-Beard neurons to signal to other neurons, not oligodendrocytes, to modulate spinal cord myelination. Together, our data support a model in which unmyelinated neurons express Nrg1 type II proteins to regulate myelination of neighboring neurons, a mode of action that may coordinate the functions of unmyelinated and myelinated neurons in the CNS.
Acta pharmacologica Sinica
Chen, ZJ;Su, CW;Xiong, S;Li, T;Liang, HY;Lin, YH;Chang, L;Wu, HY;Li, F;Zhu, DY;Luo, CX;
PMID: 36460834 | DOI: 10.1038/s41401-022-01024-z
Chronic pain patients often have anxiety disorders, and some of them suffer from anxiety even after analgesic administration. In this study, we investigated the role of AMPAR-mediated synaptic transmission in the ventromedial prefrontal cortex (vmPFC) in chronic pain-induced persistent anxiety in mice and explored potential drug targets. Chronic inflammatory pain was induced in mice by bilateral injection of complete Freund's adjuvant (CFA) into the planta of the hind paws; anxiety-like behaviours were assessed with behavioural tests; S-nitrosylation and AMPAR-mediated synaptic transmission were examined using biochemical assays and electrophysiological recordings, respectively. We found that CFA induced persistent upregulation of AMPAR membrane expression and function in the vmPFC of anxious mice but not in the vmPFC of non-anxious mice. The anxious mice exhibited higher S-nitrosylation of stargazin (an AMPAR-interacting protein) in the vmPFC. Inhibition of S-nitrosylation by bilaterally infusing an exogenous stargazin (C302S) mutant into the vmPFC rescued the surface expression of GluA1 and AMPAR-mediated synaptic transmission as well as the anxiety-like behaviours in CFA-injected mice, even after ibuprofen treatment. Moreover, administration of ZL006, a small molecular inhibitor disrupting the interaction of nNOS and PSD-95 (20 mg·kg-1·d-1, for 5 days, i.p.), significantly reduced nitric oxide production and S-nitrosylation of AMPAR-interacting proteins in the vmPFC, resulting in anxiolytic-like effects in anxious mice after ibuprofen treatment. We conclude that S-nitrosylation is necessary for AMPAR trafficking and function in the vmPFC under chronic inflammatory pain-induced persistent anxiety conditions, and nNOS-PSD-95 inhibitors could be potential anxiolytics specific for chronic inflammatory pain-induced persistent anxiety after analgesic treatment.
Singh, M;Sapkota, K;Sakimura, K;Kano, M;Cowell, RM;Overstreet-Wadiche, L;Hablitz, JJ;Nakazawa, K;
PMID: 36682446 | DOI: 10.1016/j.neuroscience.2023.01.007
N-methyl-D-aspartate receptor (NMDAR) hypofunction during brain development is likely to contribute to the manifestation of schizophrenia (SCZ) in young adulthood. The cellular targets of NMDAR hypofunction appear to be at least in part corticolimbic fast-spiking (FS) interneurons. However, functional alterations in parvalbumin (PV)-positive FS interneurons following NMDAR hypofunction are poorly understood. Paired patch-clamp recordings from murine cortical PV interneurons and pyramidal neurons revealed that genetic deletion of NMDAR subunit Grin1 in prospective PV interneurons before the second postnatal week impaired evoked- and synchronized-GABA release. Whereas intrinsic excitability and spiking characteristics were also disturbed by Grin1 deletion, neither restoring their excitability by K+ channel blockade nor increasing extracellular Ca2+ rescued the GABA release. GABA release was also insensitive to the Cav2.1 channel antagonist ω-agatoxin IVA. Heterozygous deletion of Cacna1a gene (encoding Cav2.1) in PV interneurons produced a similar GABA release phenotype as the Grin1 mutants. Treatment with the Cav2.1/2.2 channel agonist GV-58 augmented somatic Ca2+ currents and GABA release in Cacna1a-haploinsufficient PV interneurons, but failed to enhance GABA release in the Grin1-deleted PV interneurons. Taken together, our results suggest that Grin1 deletion in prospective PV interneurons impairs proper maturation of membrane excitability and Cav2.1-recruited evoked GABA release. This may increase synaptic excitatory/inhibitory ratio in principal neurons, contributing to the emergence of SCZ-like phenotypes.
McKinnon C, De Snoo ML, Gondard E, Neudorfer C, Chau H, Ngana SG, O'Hara DM, Brotchie JM, Koprich JB, Lozano AM, Kalia LV, Kalia SK
PMID: 32059750 | DOI: 10.1186/s40478-020-0894-0
Parkinson's disease is a progressive neurodegenerative disorder characterised by the accumulation of misfolded ?-synuclein in selected brain regions, including the substantia nigra pars compacta (SNpc), where marked loss of dopaminergic neurons is also observed. Yet, the relationship between misfolded ?-synuclein and neurotoxicity currently remains unclear. As the principal route for degradation of misfolded proteins in mammalian cells, the ubiquitin-proteasome system (UPS) is critical for maintenance of cellular proteostasis. Misfolded ?-synuclein impairs UPS function and contributes to neuronal death in vitro. Here, we examine its effects in vivo using adeno-associated viruses to co-express A53T ?-synuclein and the ubiquitinated reporter protein UbG76V-GFP in rat SNpc. We found that ?-synuclein over-expression leads to early-onset catalytic impairment of the 26S proteasome with associated UPS dysfunction, preceding the onset of behavioural deficits and dopaminergic neurodegeneration. UPS failure in dopaminergic neurons was also associated with selective accumulation of ?-synuclein phosphorylated at the serine 129 residue, which has previously been linked to increased neurotoxicity. Our study highlights a role for ?-synuclein in disturbing proteostasis which may contribute to neurodegeneration in vivo
Noh, YW;Yook, C;Kang, J;Lee, S;Kim, Y;Yang, E;Kim, H;Kim, E;
PMID: 35982261 | DOI: 10.1038/s42003-022-03813-y
IRSp53 (or BAIAP2) is an abundant excitatory postsynaptic scaffolding/adaptor protein that is involved in actin regulation and has been implicated in autism spectrum disorders, schizophrenia, and attention-deficit/hyperactivity disorder. IRSp53 deletion in mice leads to enhanced NMDA receptor (NMDAR) function and social deficits that are responsive to NMDAR inhibition. However, it remains unclear whether IRSp53 re-expression in the adult IRSp53-mutant mouse brain after the completion of brain development could reverse these synaptic and behavioral dysfunctions. Here we employed a brain-blood barrier (BBB)-penetrant adeno-associated virus (AAV) known as PHP.eB to drive adult IRSp53 re-expression in IRSp53-mutant mice. The adult IRSp53 re-expression normalized social deficits without affecting hyperactivity or anxiety-like behavior. In addition, adult IRSp53 re-expression normalized NMDAR-mediated excitatory synaptic transmission in the medial prefrontal cortex. Our results suggest that adult IRSp53 re-expression can normalize synaptic and behavioral deficits in IRSp53-mutant mice and that BBB-penetrant adult gene re-expression has therapeutic potential.
López-Ferreras L, Eerola K, Mishra D, Shevchouk OT, Richard JE, Nilsson FH, Hayes MR, Skibicka KP.
PMID: - | DOI: 10.1016/j.molmet.2018.11.005
Objective
The supramammillary nucleus (SuM) is nestled between the lateral hypothalamus (LH) and the ventral tegmental area (VTA). This neuroanatomical position is consistent with a potential role of this nucleus to regulate ingestive and motivated behavior. Here neuroanatomical, molecular, and behavior approaches are utilized to determine whether SuM contributes to ingestive and food-motivated behavior control.
Methods
Through the application of anterograde and retrograde neural tract tracing with novel designer viral vectors, the current findings show that SuM neurons densely innervate the LH in a sex dimorphic fashion. Glucagon-like peptide-1 (GLP-1) is a clinically targeted neuro-intestinal hormone with a well-established role in regulating energy balance and reward behaviors. Here we determine that GLP-1 receptors (GLP-1R) are expressed throughout the SuM of both sexes, and also directly on SuM LH-projecting neurons and investigate the role of SuM GLP-1R in the regulation of ingestive and motivated behavior in male and female rats.
Results
SuM microinjections of the GLP-1 analogue, exendin-4, reduced ad libitum intake of chow, fat, or sugar solution in both male and female rats, while food-motivated behaviors, measured using the sucrose motivated operant conditioning test, was only reduced in male rats. These data contrasted with the results obtained from a neighboring structure well known for its role in motivation and reward, the VTA, where females displayed a more potent response to GLP-1R activation by exendin-4. In order to determine the physiological role of SuM GLP-1R signaling regulation of energy balance, we utilized an adeno-associated viral vector to site-specifically deliver shRNA for the GLP-1R to the SuM. Surprisingly, and in contrast to previous results for the two SuM neighboring sites, LH and VTA, SuM GLP-1R knockdown increased food seeking and adiposity in obese male rats without altering food intake, body weight or food motivation in lean or obese, female or male rats.
Conclusion
Taken together, these results indicate that SuM potently contributes to ingestive and motivated behavior control; an effect contingent on sex, diet/homeostatic energy balance state and behavior of interest. These data also extend the map of brain sites directly responsive to GLP-1 agonists, and highlight key differences in the role that GLP-1R play in interconnected and neighboring nuclei.
Engstr�m Ruud L Pereira MMA, de Solis AJ, Fenselau H Br�ning JC
PMID: 31974377 | DOI: 10.1038/s41467-020-14291-3
Activation of Agouti-Related Peptide (AgRP)-expressing neurons promotes feeding and insulin resistance. Here, we examine the contribution of neuropeptide Y (NPY)-dependent signaling to the diverse physiological consequences of activating AgRP neurons. NPY-deficient mice fail to rapidly increase food intake during the first hour of either chemo- or optogenetic activation of AgRP neurons, while the delayed increase in feeding is comparable between control and NPY-deficient mice. Acutely stimulating AgRP neurons fails to induce systemic insulin resistance in NPY-deficient mice, while increased locomotor activity upon AgRP neuron stimulation in the absence of food remains unaffected in these animals. Selective re-expression of NPY in AgRP neurons attenuates the reduced feeding response and reverses the protection from insulin resistance upon optogenetic activation of AgRP neurons in NPY-deficient mice. Collectively, these experiments reveal a pivotal role of NPY-dependent signaling in mediating the rapid feeding inducing effect and the acute glucose regulatory function governed by AgRP neurons
Folorunso, OO;Brown, SE;Baruah, J;Harvey, TL;Jami, SA;Radzishevsky, I;Wolosker, H;McNally, JM;Gray, JA;Vasudevan, A;Balu, DT;
PMID: 37311798 | DOI: 10.1038/s41598-023-35615-5
The proper development and function of telencephalic GABAergic interneurons is critical for maintaining the excitation and inhibition (E/I) balance in cortical circuits. Glutamate contributes to cortical interneuron (CIN) development via N-methyl-D-aspartate receptors (NMDARs). NMDAR activation requires the binding of a co-agonist, either glycine or D-serine. D-serine (co-agonist at many mature forebrain synapses) is racemized by the neuronal enzyme serine racemase (SR) from L-serine. We utilized constitutive SR knockout (SR-/-) mice to investigate the effect of D-serine availability on the development of CINs and inhibitory synapses in the prelimbic cortex (PrL). We found that most immature Lhx6 + CINs expressed SR and the obligatory NMDAR subunit NR1. At embryonic day 15, SR-/- mice had an accumulation of GABA and increased mitotic proliferation in the ganglionic eminence and fewer Gad1 + (glutamic acid decarboxylase 67 kDa; GAD67) cells in the E18 neocortex. Lhx6 + cells develop into parvalbumin (PV+) and somatostatin (Sst+) CINs. In the PrL of postnatal day (PND) 16 SR-/- mice, there was a significant decrease in GAD67+ and PV+, but not SST + CIN density, which was associated with reduced inhibitory postsynaptic potentials in layer 2/3 pyramidal neurons. These results demonstrate that D-serine availability is essential for prenatal CIN development and postnatal cortical circuit maturation.
