Chronic Use of Intracerebral Dialysis for the In Vivo Measurement of 3,4-Dihydroxyphenylethylamine and Its Metabolite 3,4-Dihydroxyphenylacetic Acid

The intracerebral dialysis technique was studied with a method in which the rat was directly connected to the HPLC equipment. The effect of three pharmacological treatments [perfusion of 60 mmol K+ or 5 X 10(-5) M (+)-amphetamine or subcutaneous injection of 2 mg/kg (+)-amphetamine] on the release of 3,4-dihydroxyphenylethylamine (dopamine) and 3,4-dihydroxyphenylacetic acid was followed over a period of 7 days. The marked rise of dopamine output seen after infusion of K+ had almost disappeared on day 3. Tissue reactions around the membrane presumably formed a barrier preventing K+ from reaching dopaminergic terminals. In contrast, the pronounced rise in dopamine level after amphetamine (infused as well as systemically administered) was still present (although diminished) 8 days after implantation. It is concluded that, with certain restrictions, brain dialysis of dopamine is still useful several days after implantation of the membrane.     

Intracerebral Dialysis and the Blood-Brain Barrier

Abstract: The aim of the study was to evaluate how implantation of a dialysis probe influences the blood-brain barrier. Leakage of endogenous serum albumin was evaluated by Evans blue/albumin staining and by immunohistochemistry. The passage from blood to dialysate of two substances that normally do not pass into the brain, [³H]inulin and glutamate, was studied 3 and 24 h after insertion of a dialysis probe. Evans blue, given 20 min before rats were killed, was observed around the probe and surrounding brain tissue. Albumin immunoreactivity was seen at considerable distance from the probe with larger spread at 24 h than at 3 h after probe insertion. Glutamate and [³H]inulin were detected in the dialysate with no significant further increase of radioactivity after intracarotid infusion of protamine sulfate that enhances the permeability over the blood-brain barrier. When protamine was followed by infusion of glutamate, the concentrations of taurine increased in the dialysate in four of eight rats. That plasma constituents have access to the brain around the dialysis probe is essential to consider, particularly in studies using substances and drugs that do not pass an intact blood-brain barrier.     

脑内微透析采样技术及其在神经科学中的应用

作为一种新的在体化学采样技术,脑内微透析引起了神经科学家的关注。它与迅速发展起来的高灵敏度的微量分析技术相结合,实现了对体内细胞外环境中化学物质变化的动态监测,从而在神经科学领域获得应用。本系统地介绍了这一新技术的原理和方法,并扼要地介绍了一这一技术在神经科学中的应用及其取得的新进展,并结合本实验室的工作经验,对该技术存在的一些问题进行了讨论。     

Hck Promotes Neuronal Apoptosis Following Intracerebral Hemorrhage

The hematopoietic cell kinase (Hck) is a member of the Src family protein kinases which regulates many signal transduction pathways including cell growth, proliferation, differentiation, migration, and apoptosis. However, the expression and function of Hck after intracerebral hemorrhage (ICH) are unknown. Western blot, immunohistochemistry, and immunofluorescence showed that Hck was obviously up-regulation in neurons adjacent to the hematoma after ICH. In addition, the temporary raise of Hck expression was paralleled with the expression of p53, Bax, and active caspase-3, suggesting that Hck was involved in neuronal apoptosis. Hck siRNA dramatically decrease hemin-induced expression of p53, Bax, and active caspase-3 as well as the amount of apoptotic SH-SY5Y cells in vitro. Furthermore, Hck interacted with p53. Hence, Hck might promote neuronal apoptosis via p53 signaling pathway after ICH.     

Intracerebral site of convulsant action of bicuculline

Bicuculline was injected intracerebrally in several forebrain sites of the rat. In a discrete area in the vicinity of prepiriform cortex, a single, unilateral injection of bicuculline (49 pmol) produced generalized clonic seizures documented behaviorally and electroencephalographically. This is the first identification of an anatomical site from which generalized seizures can be elicited by low doses of a chemoconvulsant.     

Intracerebral hematoma complicating split calvarial bone-graft harvesting

A case is reported of an intracerebral hematoma following the harvest of split calvarial bone. Full recovery by the patient occurred. Complications following calvarial bone graft harvest are reviewed. Potential devastating complications warrant serious consideration of alternative sources of bone, especially in the purely elective surgical candidate.     

Secondary Intracerebral Blastomycosis with Giant Yeast Forms

Secondary central nervous system (CNS) blastomycosis is an unusual manifestation of blastomycosis. We report a case of recurrent intracerebral blastomycosis that presented histopathologically with giant yeast-like cells and multinucleation that mimicked Coccidioides immitis. The yeast forms of Blastomyces dermatitidis usually range in size from 8 to 20 μm in diameter. Large or giant yeast forms (20–40 μm) are rare. The four cases previously reported in the literature involving giant yeast cell forms of B. dermatitidis are reviewed here. Intracerebral blastomycosis should be suspected in patients with signs and symptoms of CNS lesions and histories of primary blastomycosis, or treatment with corticosteroids, or comprised immune systems. The diagnosis should be confirmed by culture which presents typical biphasic microbiologic features.     

Intracerebral oxytocin modulates sleep-wake behaviour in male rats

Oxytocin released within the brain under basal conditions and in response to stress is differentially involved in the regulation of the hypothalamo-pituitary-adrenal (HPA) axis. Because the HPA axis plays an important role in the regulation of wakefulness, central oxytocin may modulate sleep-wake behaviour. In the present vehicle-controlled study, we assessed the influence of a selective oxytocin receptor antagonist (des-Gly-NH2d(CH2)5 [Tyr(Me)2,Thr4] OVT; 0.75 microg/5 microl) or of synthetic oxytocin (0.1 microg and 1 microg/5 microl), infused into the lateral ventricle (i.c.v.), on the sleep pattern in male Wistar rats (n=7). Compared to vehicle, the oxytocin antagonist slightly but persistently increased wakefulness at the expense of all sleep states. This finding indicates that endogenous brain oxytocin promotes sleep. However, acute icv infusion of oxytocin delayed sleep onset latency, which resulted in a transient reduction of non-REMS and REMS, and augmented high-frequency activity in the electroencephalogram (EEG) within non-REMS. These observations agree with previous reports that icv oxytocin induces a state of arousal. Based on these findings, we postulate that oxytocin has a dual mechanism of action in dependence of the physiological state. Under basal, stress-free conditions, endogenous oxytocin may promote sleep. Conversely, the high brain levels of oxytocin after central oxytocin infusion may reflect a condition of stress accompanied by behavioural arousal and, possibly via an excitatory action on the CRH system, increase vigilance.     

Modeling Intracerebral Hemorrhage Growth and Response to Anticoagulation

The mechanism for hemorrhage enlargement in the brain, a key determinant of patient outcome following hemorrhagic stroke, is unknown. We performed computer-based stochastic simulation of one proposed mechanism, in which hemorrhages grow in “domino” fashion via secondary shearing of neighboring vessel segments. Hemorrhages were simulated by creating an initial site of primary bleeding and an associated risk of secondary rupture at adjacent sites that decayed over time. Under particular combinations of parameters for likelihood of secondary rupture and time-dependent decay, a subset of lesions expanded, creating a bimodal distribution of microbleeds and macrobleeds. Systematic variation of the model to simulate anticoagulation yielded increases in both macrobleed occurrence (26.9%, 53.2%, and 70.0% of all hemorrhagic events under conditions simulating no, low-level, and high-level anticoagulation) and final hemorrhage size (median volumes 111, 276, and 412 under the same three conditions), consistent with data from patients with anticoagulant-related brain hemorrhages. Reversal from simulated high-level anticoagulation to normal coagulation was able to reduce final hemorrhage size only if applied relatively early in the course of hemorrhage expansion. These findings suggest that a model based on a secondary shearing mechanism can account for some of the clinically observed properties of intracerebral hemorrhage, including the bimodal distribution of volumes and the enhanced hemorrhage growth seen with anticoagulation. Future iterations of this model may be useful for elucidating the effects of hemorrhage growth of factors related to secondary shearing (such as small vessel pathology) or time-dependent decay (such as hemostatic agents).     

A Rapid Method for Locating Intracerebral Electrode Tracks

This method consists of: (1) cutting formalin-fixed frozen sections 160μ thick of the brain of experimental animals, (2) mounting the unstained sections in glycerol under a cover slip, and (3) photographing their enlarged images on Kodak Direct Positive paper. The results resemble photographs of myelin sheath preparations. Direct positive photography eliminates the time needed for tediously tracing projected images, usually done on stained sections. With this method it is possible to obtain a histological analysis of a neurophysiological experiment on the following day.