## 1 Introduction
Some studies noticed, as a peripheral remark, that an increasing Ngb expression was correlated to attenuated cognitive deficit [31] and described Ngb and other molecules (neurokinin-A, catalase) as potential blood markers for generalized anxiety disorders [32,33]. Ngb, as well \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & Time & Reported \\  & & & measurements \\ \cline{3-4} \multirow{2}{*}{[3]} & Restraining & & \(\uparrow\) serum \\  & 6 h/day & & corticosterone, \\  & & & adrenaline \\  & & & \(\uparrow\) hippocampal ROS, \\  & & & NO, MDA, \(\downarrow\) TAC \\ \hline \multirow{2}{*}{[4]} & Restraining 1 h/day & & \(\uparrow\) hippocampal MDA, \\  & & & ROS, \(\downarrow\) TAC \\ \hline \multirow{4}{*}{[5]} & Corticosterone 10–40 \(\mu\)g/Kg & & \(\downarrow\) hippocampal TAC, \\  & & & \(\uparrow\) hippocampal \\  & & & MDA, \& ROS \\ \hline \multirow{2}{*}{[5]} & Restraining 4 h/day & & \(\downarrow\) hippocampal TAC, \\  & & & \(\uparrow\) hippocampal \\  & & & MDA, ROS \\ \hline \hline \end{tabular} ROS—Reactive Oxygen Species, NO—nitric oxide, MDA—malondialdehydedehyde, TAC—total antioxidant capacity.  
\end{table} 
Table 1: Experimental designs of restraint stress based on physical restraining or corticosterone injection in rats. as cytoglobin, in the absence of ligands (e.g., oxygen), showed hexacoordination by distal histidine, which contrasted the pentacordination hem geometry seen in deoxygenated hemoglobin and myoglobin. Ngb displayed a high-affinity oxygen binding of approx. 1 Torr, and occurred at \(\upmu\)M concentrations in the neurons as well as endocrine tissues [34]. However, the clear physiological function of Ngb is still unknown, besides Ngb intervention in hypoxia/stroke reactions that were noticed as enhancers for Ngb expression. The involvement of Ngb in cancer progression was also questionable. This ectopic role of the Ngb was derived from the cytoglobin function noticed as a cancer progression protein that was over-expressed in different types of tumors (non-small cell lung cancer, esophageal cancer, or melanoma) [34; 35]. Our study was performed to investigate the role of stress in Ngb expression as a pivotal protein in brain oxidative stress with expected involvements in anxiety, as was suggested by previous results and other studies [33; 36; 37; 38]. Alternatively, we have investigated the dynamic of the Ngb expression related to a gene-expression regulator methyl-CpG-binding protein 2 (MeCP2) and the time-dependent activation of the Ngb and CNP+ oligodendrocytes (2',3'-cyclic nucleotide 3'-phosphodiesterase OCs) couple. Few data were reported about Ngb and glial cells. Ngb was expressed in neurons but also in astrocytes and microglia. An expression link between Ngb and oligodendrocytes has not been demonstrated yet. However, a correlation between OCs and Ngb was noticed in neurodegenerative disorders, autism-spectrum disorders, heavy metals toxicosis, stroke, or traumatic brain injuries [39; 40; 41]. The research setup was started in previous studies, where Ngb was noticed with different expression patterns [36] in the frontal cortex after long-term treatment with metformin. The expression of the globins may also be ambiguously influenced by the methylation process [42]. However, DNA methylation in the 5'regions of the globins genes might play a direct role in the regulation of gene expression [43]. Moreover, studies revealed that methylation of the Ngb gene influenced the tissue-specific expression pattern of the protein [44; 45]. Other studies [46; 47] have noticed that MeCP2 was involved in cytoglobin expression and in neuronal plasticity control, but available consistent data about MeCP2 and Ngb relation were not shown yet. Furthermore, MeCP2-Ngb interaction in stress also lacked knowledge that required experimental data. Our assumption had considered that all the stress reactions described until now depended on the sampling moment.