Dynamic regulation of excitatory and inhibitory synaptic transmission by growth hormone in the developing mouse brain.

Normal sensory and cognitive function of the brain relies on its intricate and complex neural network. Synaptogenesis and synaptic plasticity are critical to neural circuit formation and maintenance, which are regulated by coordinated intracellular and extracellular signaling. Growth hormone (GH) is the most abundant anterior pituitary hormone. Its deficiencies could alter brain development and impair learning and memory, while GH replacement therapy in human patients and animal models has been shown to ameliorate cognitive deficits caused by GH deficiency. However, the underlying mechanism remains largely unknown. In this study, we investigated the neuromodulatory function of GH in young (pre-weaning) mice at two developmental time points and in two different brain regions. Neonatal mice were subcutaneously injected with recombinant human growth hormone (rhGH) on postnatal day (P) 14 or 21. Excitatory and inhibitory synaptic transmission was measured using whole-cell recordings in acute cortical slices 2 h after the injection. We showed that injection of rhGH (2 mg/kg) in P14 mice significantly increased the frequency of mEPSCs, but not that of mIPSCs, in both hippocampal CA1 pyramidal neurons and L2/3 pyramidal neurons of the barrel field of the primary somatosensory cortex (S1BF). Injection of rhGH (2 mg/kg) in P21 mice significantly increased the frequency of mEPSCs and mIPSCs in both brain regions. Perfusion of rhGH (1 µM) onto acute brain slices in P14 mice had similar effects. Consistent with the electrophysiological results, the dendritic spine density of CA1 pyramidal neurons and S1BF L2/3 pyramidal neurons increased following in vivo injection of rhGH. Furthermore, NMDA receptors and postsynaptic calcium-dependent signaling contributed to rhGH-dependent regulation of both excitatory and inhibitory synaptic transmission. Together, these results demonstrate that regulation of excitatory and inhibitory synaptic transmission by rhGH occurs in a developmentally dynamic manner, and have important implication for identifying GH treatment strategies without disturbing excitation/inhibition balance.

Comprehensive Analysis of the Expression and Prognosis for MCM4 in Uterine Corpus Endometrial Carcinoma.

Background: Mini chromosome maintenance protein 4 (MCM4) belongs to the family of mini chromosome maintenance proteins (MCMs) that plays a crucial role in DNA replication and cell cycle regulation. Given that MCM4 has been reported to be aberrantly expressed in a variety of tumor tissues, and is strongly associated with poor patient prognosis, it has rarely been reported in uterine corpus endometrial carcinoma (UCEC). Methods: We explored the role of MCM4 in UCEC through multi-omics analysis, including gene expression levels, survival prognosis, the biological function of interacting proteins, immune infiltration, and diagnostic value. Finally, these results were confirmed by biological experiments. Results: MCM4 was highly expressed in various malignancies including UCEC compared to normal samples and was associated with poor prognosis in patients with UCEC [including OS (HR = 1.74, p = 0.009), PFI (HR = 1.73, p = 0.002), PFI (HR = 2.23, p = 0.003)]. In the Cox regression analysis, MCM4 was an independent prognostic biomarker. Further studies showed those interacting proteins of MCM4 were enriched in DNA repair and cell cycle. Moreover, high expression of MCM4 was accompanied by lower infiltration of immune cells such as Treg cells and B cells. The distribution of MCM4 expression in molecular and immune subtypes was significantly different (p < 0.05), with high expression in the copynumber high (CN_HIGH) molecular subtype and the IFN-gamma dominant (C2) immune subtype. RT-qPCR and immunohistochemistry results also showed that MCM4 expression was significantly upregulated in endometrial cancer tissues and negatively correlated with patient prognosis (p < 0.05). Subsequent biological experiments confirmed that MCM4 promoted cell growth and invasion and inhibited apoptosis in vitro. Conclusion: Therefore, MCM4 could be a new potential biomarker for UCEC.

Ionic Mechanisms Underlying the Excitatory Effect of Orexin on Rat Subthalamic Nucleus Neurons.

Central orexinergic system deficiency results in cataplexy, a motor deficit characterized with a sudden loss of muscle tone, highlighting a direct modulatory role of orexin in motor control. However, the neural mechanisms underlying the regulation of orexin on motor function are still largely unknown. The subthalamic nucleus (STN), the only excitatory structure of the basal ganglia, holds a key position in the basal ganglia circuitry and motor control. Previous study has revealed a wide distribution of orexinergic fibers as well as orexin receptors in the basal ganglia including the STN. Therefore, in the present study, by using whole-cell patch clamp recording and immunostaining techniques, the direct effect of orexin on the STN neurons in brain slices, especially the underlying receptor and ionic mechanisms, were investigated. Our results show that orexin-A elicits an excitatory effect on STN neurons in rats. Tetrodotoxin (TTX) does not block the orexin-induced excitation on STN neurons, suggesting a direct postsynaptic action of the neuropeptide. The orexin-A-induced inward current on STN neurons is mediated by the activation of both OX1 and OX2 receptors. Immunofluorescence result shows that OX1 and OX2 receptors are co-expressed and co-localized in STN neurons. Furthermore, Na+-Ca2+ exchangers (NCXs) and inward rectifier K+ channels co-mediate the excitatory effect of orexin-A on STN neurons. These results demonstrate a dual receptor in conjunction with the downstream ionic mechanisms underlying the excitatory action of orexin on STN neurons, suggesting a potential modulation of the central orexinergic system on basal ganglia circuitry as well as its related motor control and motor diseases.

Regularizing firing patterns of rat subthalamic neurons ameliorates parkinsonian motor deficits.

The subthalamic nucleus (STN) is an effective therapeutic target for deep brain stimulation (DBS) for Parkinson's disease (PD), and histamine levels are elevated in the basal ganglia in PD patients. However, the effect of endogenous histaminergic modulation on STN neuronal activities and the neuronal mechanism underlying STN-DBS are unknown. Here, we report that STN neuronal firing patterns are more crucial than firing rates for motor control. Histamine excited STN neurons, but paradoxically ameliorated parkinsonian motor deficits, which we attributed to regularizing firing patterns of STN neurons via the hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) channel coupled to the H2 receptor. Intriguingly, DBS increased histamine release in the STN and regularized STN neuronal firing patterns under parkinsonian conditions. HCN2 contributed to the DBS-induced regularization of neuronal firing patterns, suppression of excessive ß oscillations, and alleviation of motor deficits in PD. The results reveal an indispensable role for regularizing STN neuronal firing patterns in amelioration of parkinsonian motor dysfunction and a functional compensation for histamine in parkinsonian basal ganglia circuitry. The findings provide insights into mechanisms of STN-DBS as well as potential therapeutic targets and STN-DBS strategies for PD.

[Subthalamic nucleus: from circuits, functions to a deep brain stimulation target for the treatment of Parkinson's disease].

The subthalamic nucleus (STN) is the only excitatory glutamatergic nucleus in the basal ganglia circuitry. It not only is a key node in the classical indirect pathway, but also forms the "hyperdirect" pathway directly connecting the cortex, and even is implicated as a pacemaker for activity of whole basal ganglia. Due to the key position of STN in the basal ganglia circuitry, the STN is an optimal target for deep brain stimulation (DBS) in the neurosurgical treatment of Parkinson's disease (PD). However, the therapeutic mechanisms underlying the amelioration of parkinsonian motor dysfunctions induced by DBS on STN remain enigmatic. This paper reviews recent progresses in the studies on the input-output configurations and functions of STN in the basal ganglia circuitry, and summarizes the hypotheses for mechanisms of DBS for the treatment of motor dysfunctions in PD. Studying on the DBS mechanisms will not only help to develop strategies for treatment of PD, but also contribute to the understanding of functions of the basal ganglia circuitry.

5-HT2A receptor-mediated excitation on cerebellar fastigial nucleus neurons and promotion of motor behaviors in rats.

It has long been known that serotonergic afferent inputs are the third largest afferent population in the cerebellum after mossy fibers and climbing fibers. However, the role of serotonergic inputs in cerebellar-mediated motor behaviors is still largely unknown. Here, we show that only 5-HT2A receptors among the 5-HT2 receptor subfamily are expressed and localized in the rat cerebellar fastigial nucleus (FN), one of the ultimate outputs of the spinocerebellum precisely regulating trunk and limb movements. Remarkably, selective activation of 5-HT2A receptors evokes a postsynaptic excitatory effect on FN neurons in a concentration-dependent manner in vitro, which is in accord with the 5-HT-elicited excitation on the same tested neurons. Furthermore, selective 5-HT2A receptor antagonist M100907 concentration-dependently blocks the excitatory effects of 5-HT and TCB-2, a 5-HT2A receptor agonist, on FN neurons. Consequently, microinjection of 5-HT into bilateral FNs significantly promotes rat motor performances on accelerating rota-rod and balance beam and narrows stride width rather than stride length in locomotion gait. All these motor behavioral effects are highly consistent with those of selective activation of 5-HT2A receptors in FNs, and blockage of the component of 5-HT2A receptor-mediated endogenous serotonergic inputs in FNs markedly attenuates these motor performances. All these results demonstrate that postsynaptic 5-HT2A receptors greatly contribute to the 5-HT-mediated excitatory effect on cerebellar FN neurons and promotion of the FN-related motor behaviors, suggesting that serotonergic afferent inputs may actively participate in cerebellar motor control through their direct modulation on the final output of the spinocerebellum.

Baseline saliva level of 3-methoxy-4-hydroxyphenylglycole (MHPG) associates with a consequent cognitive decline in non-demented elderly subjects: three-years follow-up study.

The aim of the study was to explore the relation between saliva level of 3-methoxy-4-hydroxy-phenylglycol (MHPG) and a later cognitive decline in non-demented elderly subjects. We have reported that sMHPG in 214 elderly subjects living in the community (age 74.5±5.9years) was associated with scores on the Mini-Mental State Examination (MMSE) and the Frontal Assessment Battery (FAB) in 2004 to 2006 (Time A). The same cohort underwent these cognitive tests again from 2007 to 2009 (Time B). The cognitive function of the 147 of 214 subjects could be reassessed by the same cognitive tests. The score on the FAB, but not the MMSE, was significantly reduced at Time B (14.6±2.6) compared with that of Time A (15.2±1.9). There was a significant negative correlation between the baseline sMHPG and the changes in the FAB score subtracted from Time B to Time A or the scores on the FAB at Time B in men, but not at Time A. These correlations were not found in women. These data indicate that high sMHPG might be associated with subsequent cognitive decline assessed by the FAB in non-demented elderly men living in the community.

Association of saliva 3-methoxy-4-hydroxyphenylglycol levels and a later depressive state in older subjects living in a rural community: 3-year follow-up study.

OBJECTIVE: The aim of the study was to examine the association of saliva levels of 3-methoxy-4-hydroxyphenylglycol (sMHPG) with a later depressive state in older people living in a rural community. METHODS: Baseline sMHPG levels were measured in 214 older subjects followed by completion of the Beck Depression Inventory (BDI) from 2004 to 2006 (time A). The same cohort underwent BDI again from 2007 to 2009 (time B). RESULTS: One hundred forty-four subjects (44 men, 100 women) were reassessed by the BDI. Baseline sMHPG levels in men with a BDI score of ≤9 at time A and a BDI score of ≥10 at time B were significantly higher than those in men with a BDI score of ≤9 at times A and B. In men, there was a significant correlation between baseline sMHPG levels and BDI score at time B (r = 0.40, p = 0.007) but not at time A (r = 0.29, p = 0.06). This association was not significant in women. CONCLUSION: These data indicate that high sMHPG levels at time A could be associated with a later depressive state in older men living in a community.