Reciprocal functional connections of the olfactory bulbs and other olfactory related areas with the prefrontal cortex

Reciprocal putative connections of the prefrontal cortex (PFC) (agranular insular, ventral and lateral orbital region) with the ipsi and contralateral main olfactory bulb (IOB; COB), the mediodorsal thalamic nucleus (MD), the basolateral amygdaloid nucleus (BLA) and the piriform cortex (PC) were investigated with electrophysiological techniques. Evoked field responses and orthodromic unit driving, generated in PFC following electrical stimulation of the above mentioned structures, were abolished following topical application of KCl, except for COB evoked mass potentials. Thus, locally generated activity was elicited in agranular insular cortex following IOB activation, the same region where recently, the taste cortex in the rat was localized. Since gustatory-visceral afferent information reaches insular cortex via 2-3 synaptic relays, autonomic, olfactory and gustatory inputs may interact at this level, and, as suggested previously for the mouse, play a key integrative role in flavor perception. Antidromically invaded neurons, 47% of which were identified by the collision-extinction technique, were also found in PFC areas which overlapped to a considerable extent with those from which orthodromic unit responses were obtained. In particular, closely spaced neurons in ventrolateral orbital (VLO) and lateral orbital (LO) regions were antidromically invaded following IOB and PC shocks; some neurons antidromically discharged by IOB were also transsynaptically activated following PC stimulation. These findings are in agreement with recent neuroanatomical studies which demonstrate axonal projections from PFC neurons to the IOB and COB in the rat and South American armadillo. In addition, stimulation of PFC regions dorsal to the rhinal fissure mostly inhibited spontaneous unit discharges recorded at the mitral cell layer of the IOB, suggesting that this effect may be partially mediated by excitatory inputs of prefrontal axons onto granule cells. The conduction properties, antidromic thresholds and activity-dependent variations in conduction velocity (CV) of bulbopetal neurons in prefrontal cortex were found to be similar to those exhibited by cells projecting to the IOB from olfactory peduncle regions, but not to those present in bulbopetal neurons of the horizontal limb of diagonal band, indicating that the OB may be subjected to centrifugal control by at least two cell groups differing in both histochemical and electrophysiological properties.     

Bidirectional effects of beta-carbolines in rats with spontaneous petit mal-like scizures

Seven benzodiazepine-receptor ligands of the beta-carbolines' group were administered IP in Wistar rats from (1) a strain displaying spontaneous petit mal-like seizures (PMLS) characterized by spike and wave discharges (SWD) and, (2) a strain where no seizure is ever observed (NS). Five different types of effects were observed. (1) Injection of a full agonist (ZK 93 423) suppressed SWD in PMLS rats, in a dose-dependent manner, and induced marked sedation with alteration of EEG background activity; (2) Injection of partial agonists (ZK 95 962, ZK 91 296) suppressed SWD in PMLS rats without sedation; (3) Injection of low doses of a full inverse agonist (DMCM) significantly increased the total duration of SWD in PMLS rats and induced SWD in NS rats. Higher doses of DMCM induced convulsions in both strains; (4) Injection of partial inverse agonists (FG 7142, ZK 90 886) aggravated SWD in PMLS and induced SWD in NS rats. FG 7142 induced convulsions only in PMLS animals, whereas no convulsions were ever observed with ZK 90 886; (5) Injection of an antagonist (ZK 93 426) did not significantly modify SWD in PMLS rats. However, this compound was able to reverse both antiepileptic effects of agonists and epileptogenic effects of inverse agonists. These results suggest the involvement of the benzodiazepine-GABA receptor complex in the control of petit mal-like seizures in rats.     

Synthesis of acetylcholine by endothelial cells isolated from rat brain cortex capillaries

Choline acetyltransferase (ChAT) activity was measured in a fraction of endothelial cells obtained by collagenase digestion from previously isolated rat brain cortex capillaries. ChAT specific activity in the dissociated cells (0.264 nmol X mg protein-1 X min-1) was nearly 7 times higher than the activity measured in 'capillary-forming' cells (0.038 nmol X mg protein-1 X min-1). It is not known whether this increase was caused by ChAT enrichment of the former cellular fraction, and/or by a change in the specific activity of the enzyme during the isolation procedure, but the finding would be in favor of the intrinsic localization of cerebrovascular ChAT in endothelial cells. This would support the hypothesis of a role for locally synthesized ACh in the vasodilating response to noxious stimuli.     

Determination of molecular forms of brain acetylcholinesterase: Technical considerations

Sucrose density centrifugation has been used to characterize the relative levels of AChE molecular forms in different parts of the brain, during development, or in various disease states. We have examined the influence of various tissue or sample storage and handling techniques on the abundance of the 4S and 10S molecular forms of AChE in rat forebrain. Our results demonstrate that freezing either a subcellular fraction or the intact tissue causes dramatic shifts in the level of the 4S and 10S molecular forms as compared to the values obtained in fresh tissue. Total AChE activity was unchanged suggesting that 4S and 10S forms are equally active and that 4S AChE is easily dissociated from 10S. These observations suggest that 4S and 10S molecular forms in brain are extremely labile and that great care should be taken when studying the factors that regulate these forms.     

Organization of ventral tegmental area cells projecting to the occipital cortex and forebrain in the rat

Our horseradish peroxidase retrograde tracing study revealed a specific subpopulation of ventral tegmental area (VTA) neurons that send axons to the occipital cortex in the rat. A fluorescent retrograde tracing study demonstrated that neuronal populations in the VTA projecting to the occipital cortex are distributed in a manner separate from those projecting to forebrain structures such as the frontal/anterior cingulate cortices and nucleus accumbens. The scarcity of collateral projections from the VTA contrasts with the extensive collateralization of projection neurons in the substantia nigra pars compacta. Projections to the occipital cortex may define the distribution of cells comprising the VTA and thus the clear hodological separation of the A9 and A10 dopamine cell groups.     

Magnesium protects against neurological deficit after brain injury

The biochemical factors that mediate secondary or delayed damage to the central nervous system (CNS) remain speculative. We have recently demonstrated that brain injury in rats causes a rapid decline in brain intracellular free magnesium (Mg2+) and total magnesium concentrations that is significantly correlated with the severity of injury. In order to further investigate the relationship between Mg2+ and brain injury, we examined the effect of Mg2+ treatment on posttraumatic neurological outcome following fluid-percussion brain injury (2.0 atm) in rats. Since administration of ATP-MgCl2 has been shown to be beneficial in a variety of models of organ ischemia, we also examined the efficacy of ATP-MgCl2 or ATP alone in the treatment of experimental brain injury. Animals treated with low (12.5 mumol) or high (125 mumol) dose MgCl2 at 30 min postinjury showed a significant dose-dependent improvement in neurological function when compared to saline-treated controls. Treatment with ATP-MgCl2 (12.5 mumol) or ATP alone (12.5 mumol) caused no significant improvement in chronic neurological outcome. MgCl2-treated animals showed no change in postinjury mean arterial blood pressure (MAP), whereas animals treated with either ATP-MgCl2 or ATP alone showed a transient but significant fall in MAP (P less than 0.01) during the drug-infusion period. Our results suggest that postinjury treatment with MgCl2 is effective in limiting the extent of neurological dysfunction following experimental traumatic brain injury in the rat.     

大鼠脑出血后脑组织MMP-2、MMP-9表达及其与脑水肿关系的研究

目的研究大鼠脑出血后基质金属蛋白酶-2、基质金属蛋白酶-9的表达规律及其与脑水肿之间的关系。方法采用向大鼠尾状核注射自体不凝血制作大鼠脑出血模型,实验动物随机分为假手术对照组和脑出血组,免疫组化法测定脑组织MMP-2、MMP-9的表达及干湿重法测定脑组织含水量。结果（1）血肿边缘MMP-9阳性微血管数在脑出血6h明显升高（P〈0.01）,48h达高峰,2w降至零表达（P〉0.05）;MMP-248h始在巨噬细胞上表达（P〈0.05）,120h达高峰,2w仍保持较高水平（P〈0.01）;（2）脑组织含水量在脑出血12h显著增加（P〈0.05）,72h达到高峰,2w与假手术对照组无差异（P〉0.05）。（3）脑出血后MMP-9与脑组织含水量之间呈正相关关系（r=0.8716,P〈0.01）。结论脑出血后MMP-2、MMP-9有高表达,MMP-9参与了脑出血急性期脑水肿的形成,MMP-2则可能参与了脑出血后期的脑组织损伤修复。     

肝硬化大鼠脑水通道蛋白-4、胶质纤维酸性蛋白表达与脑水肿关系

目的观察肝硬化大鼠脑组织中AQP-4和GFAP的表达并探讨其和脑水肿发生的关系.方法硫代乙酰胺法建立肝硬化大鼠模型;脑MR DWI扫描,测定DWI、ADC值;检测动脉血氨水平;免疫组化图像分析脑组织中AQP-4、GFAP表达水平:观察大脑星形胶质细胞形态、血脑屏障超微结构变化.结果成功建立肝硬化大鼠模型;对照组MRI DWI扫描在感兴趣区域信号无差异(P＞0.05);肝硬化组和对照组间动脉血氨水平无差异(P＞0.05);肝硬化组大鼠脑组织中AQP-4、GFAP表达增高(P＜0.05).病理观察发现血管周围间隙增加,电镜下见轻微脑星形胶质细胞水肿,血脑屏障无改变.结论肝硬化大鼠脑组织中AQP-4、GFAP表达上调并伴有隐性的细胞水肿,GFAP表达增加和正常的血氨水平可能减轻AQP-4对脑水肿发生的影响.     

胰岛素样生长因子1受体抗体对大鼠血管平滑肌细胞增殖的影响

目的观察胰岛素样生长因子1受体抗体对大鼠血管平滑肌细胞增殖的影响。方法球囊导管损伤大鼠一侧颈总动脉,7天后体外培养受损血管的中膜平滑肌细胞,以损伤侧血管细胞为实验组,以对侧正常血管中膜平滑肌细胞为对照组;采用-αactin免疫细胞化学法进行细胞鉴定;在细胞的培养悬液中加入不同浓度的胰岛素样生长因子1受体抗体作用24 h,然后采用5-溴-2脱氧尿苷细胞增殖检测法检测细胞的增殖程度。结果大鼠颈总动脉球囊损伤后,体外培养的中膜平滑肌细胞表现出显著的增殖性(与对照组比较,P<0.01);胰岛素样生长因子1受体抗体可以显著抑制大鼠平滑肌细胞的增殖,呈现出浓度依赖性特征(组间比较,P<0.01)。结论胰岛素样生长因子1受体抗体具有抑制平滑肌细胞增殖的作用,有望用于治疗平滑肌细胞增殖性疾病。     

淫羊藿甙、菟丝子提取物对雄激素部分缺乏大鼠生殖保护作用的比较研究

目的 探讨淫羊藿甙、菟丝子提取物对雄激素部分缺乏大鼠的生殖保护作用.方法 以环磷酰胺造成生殖系统受损、雄激素部分缺乏大鼠模型,灌胃淫羊藿甙和菟丝子提取物7 d后,检测血清睾酮、黄体生成素（LH）、卵泡刺激素（FSH）含量;以HE染色和原位末端标记法（TUNEL）检测,光镜下观察睾丸组织、阴茎海绵体平滑肌细胞变化情况.结果 ①血清睾酮水平：淫羊藿甙组明显高于空白组和模型组,但低于睾酮组（P＜0.05）;菟丝子提取物组高于模型组,低于睾酮组（P＜0.05）,但与空白组间无统计学差异.②血清LH、FSH水平各组间均未见明显统计学差异.③阴茎海绵体平滑肌细胞的凋亡率：睾酮组和淫羊藿甙组明显低于模型组（P＜0.05）;菟丝子组与模型组则未见明显统计学差异.结论 淫羊藿甙、菟丝子提取物对雄激素部分缺乏大鼠均具有生殖保护作用,但淫羊藿甙作用效果强于菟丝子提取物.