The effect of ischemia on biogenic amine concentrations in the central nervous system

Diffusion Kurtosis Imaging and Pathology in Spinal Cord Ischemia/Reperfusion Injury in Rabbits: A Case-Control Study

Background

The aim of this study was to evaluate the application of diffusion kurtosis imaging (DKI) in spinal cord ischemia/reperfusion (SCI/R) injury and to explore its association with pathology.

Material/Methods

Japanese male long-eared rabbits were chosen and divided into 7 groups (8 rabbits in each group): control group (C group), sham-operation control group (S group), and 5 experimental groups (E-2 h group, E-24 h group, E-48 h group, E-7 d group, and E-14 d group). Tarlov scoring and immunohistochemical staining were used to assess hindlimb motor function and observe the expression of glial fiber acidic protein (GFAP), respectively. The correlation between DKI and pathology after SCI/R injury was compared by 3.0TMR scanning DKI.

Result

Neuroethology in each time point of E groups was significantly different from that in C and S groups (P<0.05). The E-24 h group had the lowest value (P<0.05), and the hindlimb motor function began to recover after 24 h. The expression of GFAP was gradually increased after SCI/R injury, and the maximum value was in the E-7 d group (P<0.05). MK (mean kurtosis) had a linear negative correlation with average optical density (OD) (r=−0.115, P<0.05) and was positively correlated with integral OD (IOD) (r=0.204, P<0.05), in which MD (mean dispersion) was positively correlated with OD and IOD, but without a significant difference (r=0.618, r=251, P>0.05).

Conclusions

DKI can be used to monitor the changes in SCI/R injury, and fractional anisotropy (FA) can reflect change in white matter structure. The changes in expression of MK and GFAP were related to the myelin sheath injury repair process.

Neuropathogenesis of delirium: review of current etiologic theories and common pathways

Delirium is a neurobehavioral syndrome caused by dysregulation of neuronal activity secondary to systemic disturbances. Over time, a number of theories have been proposed in an attempt to explain the processes leading to the development of delirium. Each proposed theory has focused on a specific mechanism or pathologic process (e.g., dopamine excess or acetylcholine deficiency theories), observational and experiential evidence (e.g., sleep deprivation, aging), or empirical data (e.g., specific pharmacologic agents' association with postoperative delirium, intraoperative hypoxia). This article represents a review of published literature and summarizes the top seven proposed theories and their interrelation. This review includes the "neuroinflammatory," "neuronal aging," "oxidative stress," "neurotransmitter deficiency," "neuroendocrine," "diurnal dysregulation," and "network disconnectivity" hypotheses. Most of these theories are complementary, rather than competing, with many areas of intersection and reciprocal influence. The literature suggests that many factors or mechanisms included in these theories lead to a final common outcome associated with an alteration in neurotransmitter synthesis, function, and/or availability that mediates the complex behavioral and cognitive changes observed in delirium. In general, the most commonly described neurotransmitter changes associated with delirium include deficiencies in acetylcholine and/or melatonin availability; excess in dopamine, norepinephrine, and/or glutamate release; and variable alterations (e.g., either a decreased or increased activity, depending on delirium presentation and cause) in serotonin, histamine, and/or γ-aminobutyric acid. In the end, it is unlikely that any one of these theories is fully capable of explaining the etiology or phenomenologic manifestations of delirium but rather that two or more of these, if not all, act together to lead to the biochemical derangement and, ultimately, to the complex cognitive and behavioral changes characteristic of delirium.

Pathoetiological model of delirium: a comprehensive understanding of the neurobiology of delirium and an evidence-based approach to prevention and treatment

Delirium is the most common complication found in the general hospital setting. Yet, we know relatively little about its actual pathophysiology. This article contains a summary of what we know to date and how different proposed intrinsic and external factors may work together or by themselves to elicit the cascade of neurochemical events that leads to the development delirium. Given how devastating delirium can be, it is imperative that we better understand the causes and underlying pathophysiology. Elaborating a pathoetiology-based cohesive model to better grasp the basic mechanisms that mediate this syndrome will serve clinicians well in aspiring to find ways to correct these cascades, instituting rational treatment modalities, and developing effective preventive techniques.

Effect of the serotonin antagonist ketanserin on the hemodynamic and morphological consequences of thrombotic infarction

The effect of the serotonin (5-hydroxytryptamine, 5-HT) antagonist ketanserin on the remote hemodynamic consequences of thrombotic brain infarction was studied in rats. Treated rats received an injection of 1 mg/kg ketanserin 30 min before and 1 h following photochemically induced cortical infarction. Local CBF (LCBF) was assessed autoradiographically with [14C]iodoantipyrine 4 h following infarction, and chronic infarct size was documented at 5 days. Thrombotic infarction led to significant decreases in LCBF within noninfarcted cortical regions. For example, mean LCBF was decreased to 63, 55, and 65% of control (nontreated normal rats) in ipsilateral frontal, lateral, and auditory cortices, respectively. In rats treated with ketanserin, significant decreases in LCBF were not documented within remote cortical areas compared with controls. In contrast to these hemodynamic effects, morphological analysis of chronic infarct size demonstrated no differences in infarct volume between treated (27 +/- 3 mm3) and nontreated (27 +/- 6 mm3) rats. These data are consistent with the hypothesis that 5-HT is involved in the widespread hemodynamic consequences of experimentally induced thrombotic infarction. Remote hemodynamic consequences of acute infarction can be inhibited without altering final infarct size.

CSF cyclic AMP and CSF adenylate kinase in cerebral ischaemic infarction

The severity of neurological deficits, size of hypodense zone on CT, concentration of cAMP and activity of adenylate kinase in cerebrospinal fluid (CSF) were evaluated at predefined intervals in the acute stage of supratentorial cerebral ischaemic infarction in 52 patients. Patients with cerebral infarction had raised activities of adenylate kinase CSF as compared with normal persons. Patients with marked neurological deficits, only slight improvement of neurological signs and large infarction zones on CT had higher average activities of adenylate kinase and lower concentration of cAMP in CSF. Alterations of CSF adenylate kinase and CSF cAMP values were most distinct on the 3rd day after the stroke. Reasons for the changes may be metabolic disorders following brain ischaemia.