[3H] Ketanserin binds to non-5-HT2 sites in rabbit cerebral cortex and neostriatum

A characterization of [³H]ketanserin ([³H]KTS) binding in the frontal cortex (fCTX) and neostriatum (caudate-putamen, CPU) of rabbit was carried out to determine whether this ligand labels a non-serotoninergic receptor. The association and dissociation kinetics in fCTX were rapid, and could be fitted to two-site models, suggesting [³H]KTS is labeling two cortical sites. Using the serotonin-2 (5-HT₂) antagonist mianserin to determine nonspecific binding, the saturation curves revealed a single high-affinity binding site. In contrast, when unlabeled ketanserin was used for nonspecific counts, the Scatchard plots were best fitted to a two-site model but the binding parameters of the high-affinity site were similar to that obtained in the presence of mianserin. The 5-HT₂ antagonists mianserin, methysergide and ritanserin inhibited [³H]KTS binding in fCTX at nanomolar concentrations, however, the curves were best fitted to two-site models. In contrast, [³H]KTS binding to membrane preparations from the CPU could only be inhibited by high (micromolar) concentrations of these antagonists. Low micromolar concentrations of the monoamine uptake blockers GBR12909, desipramine, nomifensine, cocaine and fluoxetine competed with [³H]KTS in both fCTX and CPU. This study demonstrates that [³H]KTS labels a non-serotoninergic recognition site in the rabbit fCTX and CPU similar to that found in the rat neostriatum, i.e.: probably a monoamine transport site.     

Postmortem Human Brain pH and Lactate in Sudden Infant Death Syndrome

Lactate and pH were measured in frontal and temporal cortex, cingulate gyrus, and caudate nucleus in brains from sudden infant death syndrome (SIDS) cases, control infants, and control adults. Both the lactate levels and the pH values were significantly correlated (p less than 0.001) between the four brain areas, whereas lactate and pH values were significantly correlated within each brain area (p less than 0.001) with a value of pH 7.2 for zero lactate. The lactate concentration in heart blood was significantly correlated with brain lactate (p less than 0.001). Adult sudden death cases (heart attacks) had low lactate and high pH values, whereas agonal state cases had high lactate and low pH values. Control infants who had died because of accidents also had low lactate and high pH values, but infants who might have been exposed to hypoxia before death had high lactate and low pH values. SIDS cases fell into two groups: the first, consisting of all victims over 30 weeks of age and about one-half to two-thirds of those aged less than 30 weeks, had low lactate and high pH values; the second group, consisting of about one-third to one-half of those less than 30 weeks old, had high lactate and low pH values. The changes in lactate levels and pH values indicate that the majority of SIDS cases had died suddenly, but that a sizeable minority had been exposed to hypoxia prior to death.     

Effects of sodium,lithium, and magnesium onIn vitro binding of [3H]SCH23390 in rat neostriatum and cerebral cortex

The effects of sodium, lithium, and magnesium on the in vitro binding properties of the D₁ antagonist [³H]SCH23390 were examined with membrane preparations from rat neostriatum (CPU; caudate-putamen) and cerebral cortex (CTX). The saturation binding isotherms for both tissues performed in the presence of 120 mM of either Na⁺ or Li⁺ revealed an increase in the affinity, as compared to that observed when the incubation buffer was composed of Tris-Cl 50 mM with MgCl₂ 1 mM alone. For the CPU there were no changes in the maximum binding capacity (B _max) in the different buffers used. In the case of the CTX, there was a loss of [³H]SCH23390 binding sites when either Na⁺ or Li⁺ 120 mM were added to the incubations, suggesting a lack of selectivity of this ligand in the absence of group IA cations. The agonist state of the [³H]SCH23390 binding site was studied in competition experiments with dopamine. The highest agonist affinity was obtained in 50 mM Tris-Cl buffer with 1 mM MgCl₂ while the addition of 120 mM of either Na⁺ or Li⁺ caused a 3- to 5-fold decrease in the potency of dopamine to compete with specific [³H]SCH23390 binding in both CPU and CTX. The presence of magnesium was essential for the competition experiments; i.e.: a concentration of 1 mM MgCl₂ was optimum to obtain dopamine antagonism of ligand binding, while increasing Mg²⁺ to 2 or 5 mM did not appear to further improve the inhibitions. The results support both agonist and antagonist affinity shifts for the dopamine D₁ receptor labeled with [³H]SCH23390. Receptor affinity studies should take into account that pharmacological specificity may vary with the incubation buffer utilized, especially when comparing binding data from different laboratories performed under varying ionic conditions.     

Age-related telomere attrition in the human putamen

Age is a major risk factor for neurodegenerative diseases. Shortening of leucocyte telomeres with advancing age, arguably a measure of “biological” age, is a known phenomenon and epidemiologically correlated with age-related disease. The main mechanism of telomere shortening is cell division, rendering telomere length in post-mitotic cells presumably stable. Longitudinal measurement of human brain telomere length is not feasible, and cross-sectional cortical brain samples so far indicated no attrition with age. Hence, age-related changes in telomere length in the brain and the association between telomere length and neurodegenerative diseases remain unknown. Here, we demonstrate that mean telomere length in the putamen, a part of the basal ganglia, physiologically shortens with age, like leukocyte telomeres. This was achieved by using matched brain and leukocyte-rich spleen samples from 98 post-mortem healthy human donors. Using spleen telomeres as a reference, we further found that mean telomere length was brain region-specific, as telomeres in the putamen were significantly shorter than in the cerebellum. Expression analyses of genes involved in telomere length regulation and oxidative phosphorylation revealed that both region- and age-dependent expression pattern corresponded with region-dependent telomere length dynamics. Collectively, our results indicate that mean telomere length in the human putamen physiologically shortens with advancing age and that both local and temporal gene expression dynamics correlate with this, pointing at a potential mechanism for the selective, age-related vulnerability of the nigro-striatal network.     

Chronic nicotine modifies the effects of morphine on extracellular striatal dopamine and ventral tegmental GABA

Previously, we have shown that 7-week oral nicotine treatment enhances morphine-induced behaviors and dopaminergic activity in the mouse brain. In this study, we further characterized the nicotine-morphine interaction in the mesolimbic and nigrostriatal dopaminergic systems, as well as in the GABAergic control of these systems. In nicotine-pretreated mice, morphine-induced dopamine release in the caudate putamen and nucleus accumbens was significantly augmented, as measured by microdialysis. Chronic nicotine treatment did not change basal extracellular concentrations of dopamine and its metabolites in the caudate putamen and nucleus accumbens, nor did it affect the rate of dopamine synthesis, as assessed by 3-hydroxybenzylhydrazine dihydrochloride-induced DOPA accumulation. GABAergic control of dopaminergic activity was studied by measuring extracellular GABA in the presence of nipecotic acid, an inhibitor of GABA uptake. Acute (0.3 mg/kg or 0.5 mg/kg i.p.) and chronic nicotine, as well as morphine (15 mg/kg s.c.) in control mice decreased nipecotic acid-induced increase in extracellular GABA in the ventral tegmental area/substantia nigra (VTA/SN). In contrast, in nicotine-treated mice, morphine increased GABA levels in the presence of nipecotic acid. We did not find any alterations in GABA(B)-receptor function after chronic nicotine treatment. Thus, our data show that chronic nicotine treatment sensitizes dopaminergic systems to morphine and affects GABAergic systems in the VTA/SN.     

Morphine dependence changes the role of droperidol on pain-related electric activities in caudate nucleus

Droperidol causes the blockage of the dopamine receptors in the central nervous system that are involved in pain transmission. However, the mechanism of action of droperidol in pain-related neurons is not clear, and it is still unknown whether opioids are involved in the modulation of this processing. The present study examines the effect of droperidol on the pain-evoked response of pain-excitation neurons (PENs) and pain-inhibition neurons (PINs) in the caudate nucleus (Cd) of rats. The trains of electric impulses applied to the sciatic nerve were used as noxious stimulation. Our results revealed that droperidol decreased the frequency of PEN discharge, and increased the frequency PIN discharge evoked by the noxious stimulation in the Cd of normal rats, while administration of droperidol to morphine-dependent rats produced the opposite response. Those demonstrated that droperidol is involved in the modulation of nociceptive information transmission in Cd, and there were completely opposite responses to painful stimulation between normal and morphine-dependent rats after administration of droperidol.     

Brain region-specific N-glycosylation and lipid rafts association of the rat mu opioid receptor

The mu opioid receptor (MOR) in the rat and mouse caudate putamen (CPu) and thalamus was demonstrated as diffuse and broad bands by Western blot with a polyclonal antibody against a C-terminal peptide of MOR, which were absent in the cerebellum and brains of MOR-knockout mice. The electrophoretic mobility of MOR differed in the two brain regions with median relative molecular masses (Mr’s) of 75 kDa (CPu) vs. 66 kDa (thalamus) for the rat, and 74 kDa (CPu) vs. 63 kDa (thalamus) for the mouse, which was due to its differential N-glycosylation. Rat MOR in CPu was found mainly associated with low-density cholesterol- and ganglioside M1 (GM1)-enriched membrane subdomains (lipid rafts), while the MOR in the thalamus was present in rafts and non-rafts without preference. Cholesterol reduction by methyl-β-cyclodextrin decreased DAGMO-induced [³⁵S]GTPγS binding in rat CPu membranes to a greater extent than in the thalamus membranes.     

快速周期伏安法在定量研究脑内核团多巴胺释放中的应用

目的和方法：采用快速周期伏安法（ＦＣＶ）在体研究电刺激内侧前脑束（ＭＦＢ）或腹侧背盖区（ＶＴＡ）诱发的纹状体（ＣＰｕ）、伏核（Ａｃｂ）或中央杏仁核（ＣＡＮ）多巴胺（ＤＡ）释放的特点,探索电刺激诱发不同核团ＤＡ释放的适宜刺激参数。结果：ＣＰｕ、Ａｃｂ与ＣＡＮ的ＤＡ释放量及释放动力学特征均有不同。结论：在应用ＦＣＶ技术研究脑内不同部位ＤＡ释放时,应重视适宜刺激参数的选择及运用,以获取更好的实验结果。     

大鼠尾壳核-海马癫痫电网络的神经信息编码特征

目的：观察强直电刺激大鼠右侧尾壳核（CPu）时,CPu-海马（HPC）网络癫痫的神经信息编码特征。方法：雄性SD大鼠59只。急性或慢性强直电刺激CPu（acute tetanization of the right CPu or chronic tetanization of the right CPu,ATRC or CTRC）（60Hz．0．4～0．6mA,2s）诱导大鼠癫痫模型。结果：①ATRC可以诱导双侧HPC神经元出现非对称性癫痫相关性单位电活动．增加对侧HPC单位放电时间间隔（Interspike interval,ISI）点分布的分岔角度。②CTRC可以诱导双侧CPu网络出现尖波样连续发放,同侧振荡样网络发作具有明显的相位移动特征;频率变化顺序为70Hz、110Hz、35Hz以及30Hz．与时间呈显著的负相关;振荡波波峰间隔（Interpeak interval,IPI）和波峰振幅逐渐增大,与时间呈显著正相关。③CTRC后加ATRC可以分别诱导双侧CPu网络出现原发性后放电。结论：激活CPu可以跨大脑半球重建双侧CPu—HPC癫痫电网络．其神经信息编码特征可能成为癫痫发生的神经信息学基础。