A continuous striatal infusion of 6-hydroxydopamine produces a terminal axotomy and delayed behavioral effects

Rat models of Parkinson's disease typically employ a rapid nigral injection of 6-hydroxydopamine (6-OHDA) to produce a near-complete loss of nigrostriatal dopamine neurons, and thus model end stage disease. The present report describes the use of a continuous, low dose infusion of 6-OHDA into the striatum which produces a terminal axotomy of nigrostriatal dopamine neurons and protracted behavioral response. A solution of 6-OHDA in 0.4% ascorbate, delivered at 37°C from osmotic minipumps, was stable for 8 days as determined by its retained toxicity to a dopaminergic neuroblastoma cell line. The continuous infusion of 0.2 μg 6-OHDA per h did not affect the striatal uptake of [³H]GABA, [³H]choline, or [³H]glutamate but reduced [³H]dopamine uptake by 55% within 1.5 days after the start of the infusion. The striatal infusion of 6-OHDA produced a dose-dependent reduction of striatal dopamine and DOPAC levels but did not alter HVA, 5-HT, or 5-HIAA. An increase in amphetamine-induced ipsiversive rotations occurred within 1.5 days after the acute striatal injection of 20 μg or 30 μg of 6-OHDA but required 4 days to develop with the continuous 6-OHDA infusion. The topography of the lesion mapped by [³H]mazindol binding showed that, begining by 1.5 days, a diffuse depletion of terminals encompassed much of the striatum in the 30 μg acute injection group, whereas in the continuously infused rats, the lesion was apparent only by 4 days and was restricted to a smaller and more completely lesioned area. Unlike acutely lesioned animals, continuously infused rats revealed no obvious loss of dopamine neurons in the pars compacta by 5 weeks after 6-OHDA. The continuous striatal infusion of 6-OHDA can produce a topographically limited terminal axotomy of dopamine neurons and a protracted behavioral impairment.     

Ontogenetic Development of 5-HT1D Receptors in Human Brain: An Autoradiographic Study

The pattern of pre- and postnatal appearance of 5-HT_1D receptors throughout the different areas of the human brain was studied by quantitative in vitro autoradiography, using [¹²⁵I]GTI (serotonin O -carboxymethyl-glycyl-[¹²⁵I]tyrosinamide) as a ligand. The anatomical distribution of 5-HT_1D receptors in neonatal, infant and children's brain was in good agreement with that observed in the adult, the basal ganglia and substantia nigra being the most intensely labelled areas. The development of these receptors throughout the human brain was mainly postnatal: low densities of [¹²⁵I]GTI binding sites were observed at the fetal/neonatal stage in most regions analyzed, in contrast with the high levels of labelling found in infant and children's brains. Indeed, in a number of regions, including the globus pallidus, substantia nigra and visual cortex, a peak of overexpression of 5-HT_1D receptors was observed in the first decade of life. Such overexpression could support a regulatory role for 5-HT_1D receptors in advanced periods of the CNS developmental process. Our results also indicate that the administration of drugs acting on 5-HT_1D receptors during the early postnatal period of life could result in modifications of their properties, as these receptors are already functional in this period.     

Opioid peptides and receptors in joint tissues: study in the rat.

Using immunohistochemical and biochemical techniques, the occurrence of endogenous opioid peptides and their receptors in normal rat bone and joint tissues was investigated. Opioid receptors were detected, quantified, and characterized in homogenates from capsule/synovium and periosteum using radioligand binding assays. Receptor binding of the nonselective opioid [3H]naloxone to tissue homogenates was stereospecific and saturable, showing similar characteristics to that of brain tissue, although with lower binding capacities. By immunohistochemistry, the neuronal occurrence of four different enkephalins was demonstrated in synovium, bone marrow, periosteum, and juxta-articular bone, whereas no neuronal dynorphin immunoreactivity was detected. Double-staining studies disclosed that enkephalins coexisted with substance P in primary afferent fibers. The applied techniques can be used to assess changes in the distribution of endogenous opioids and their receptors in joint tissues in conditions associated with pain and inflammation. The endogenous opioid system now demonstrated might be targeted and exploited therapeutically to obtain peripheral control of symptoms in joint disorders.     

In vivo receptor binding,neurochemical and functional studies with the dopamine D-1 receptor antagonist SCH 23390

Summary A series of in vivo experiments were undertaken, relating functional (motor activity, body temperature), dopamine (DA) receptor binding and neurochemical (catecholamine synthesis and utilization, DA release) aspects of the pharmacology of SCH 23390 in the rat.The compound inhibited the locomotor hyperactivity, but not the hypothermia, induced by the potent DA stimulant DP-5,6-ADTN. Interstingly, SCH 23390 simultaneously failed to displace DP-5,6-ADTN from its binding sites in the rat striatum—used as a direct in vivo biochemical index of DA (D-2) receptor interaction. The spontaneous locomotion in non-pretreated rats was likewise inhibited by SCH 23390. The locomotor-suppressive action, but not the DP-5,6-ADTN-displacing capcity of the D-2 blocker haloperidol was significantly enhanced by SCH 23390, suggesting that motility can be suppressed by either enhanced D-1 or D-2 (postsynaptic) receptor blockade, but also that the D-1 and D-2 sites involved may be physically distinct.SCH 23390 only slightly altered in vivo neurochemical of DA synthesis, release and nerve-impulse flow, indicating that, while similar in suppressing dopaminergic behaviour, the D-1 antagonist is less effective than traditional neuroleptics as an activator of DA neuronal feedback mechanisms. The weak increases of DA synthesis and release nonetheless obtained were equal in magnitude (30–40%) in the limbic vs. striatal brain areas; also in this respect, SCH 23390 thus differs from classical neuroleptics, which generally display more marked effects in the striatum than in limbic tissue.No major changes in the in vivo indices of NA synthesis and utilization (or in 5-HT synthesis) were found after SCH 23390 administration, by and large supporting the DA receptor specificity of the compound.In summary, the studies demonstrated that SCH 23390 can offset and accentuate, respectively, behavioural consequences of D-2 receptor stimulation and blockade. Importantly, at the same time no direct interaction at the level of D-2 DA receptor sites in the striatum was detected. Only slight, D-2 antagonist-like, changes in neurochemical indices of dopaminergic activity were observed after D-1 receptor blockade by means of SCH 23390. With regard to DA agonist hypothermia, SCH 23390 was without effect per se, but (at a high dose) attenuated the action of the D-2 antagonist haloperidol. The observations may indicate that the complex interactions between central D-1 and D-2 receptor-controlled mechanisms that influence behaviour, neurochemistry, and possibly autonomic nervous expression, are not identical.     

Day-to-day variations in serum iron,serum iron binding capacity,serum ferritin and erythrocyte protoporphyrin concentrations in anaemic subjects

Day-to-day variations in serum iron, serum iron binding capacity, serum ferritin and erythrocyte protoporphyrin were determined on 2 successive days in 48 patients with anaemia. The correlation coefficients between the paired determinations were 0.86, 0.89, 0.95 and 0.95, and the day-to-day coefficients of variation (in per cent) were 33, 11, 12 and 13 for serum iron, serum iron binding capacity, erythrocyte protoporphyrin and serum ferritin, respectively. Thus, in patients with anaemia, day-to-day variations in serum iron, serum iron binding capacity, erythrocyte protoporphyrin and serum ferritin are at least as high as in healthy controls. The results indicate important limitations in the use, particularly, of serum iron in the clinical investigation of anaemia.     

Paucity of glutaminase-immunoreactive nonpyramidal neurons in the rat cerebral cortex.

Glutaminase has been considered to be a synthesizing enzyme of transmitter glutamate in pyramidal neurons of the cerebral cortex. In the present study, an attempt was made to examine with a double immunofluorescence method whether or not nonpyramidal neurons of the cerebral cortex are immunoreactive for glutaminase. Glutaminase was stained with mouse anti-glutaminase IgM and FITC-labeled anti-[mouse IgM] antibody. In the same section, parvalbumin (PA), calbindin (CB), choline acetyltransferase (CAT), vasoactive intestinal polypeptide (VIP), corticotropin releasing factor (CRF), cholecystokinin (CCK), somatostatin (SS), or neuropeptide Y (NPY) was visualized as a marker for nonpyramidal neurons with an antibody to each substance, biotinylated secondary antibody and Texas Red-labeled avidin. Virtually no glutaminase immunoreactivity was seen in PA-, CB-, CAT-, VIP-, CRF-, CCK-, SS-, or NPY-immunoreactive neuronal perikarya in the neocortex and mesocortex (cingulate and retrosplenial cortices), although it was detected in a few PA-, CB-, VIP-, CCK-, SS-, or NPY-immunoreactive nonpyramidal neurons in the piriform, entorhinal, and hippocampal cortices. PA- and CB-positive neurons have been reported to constitute the major population of GABAergic neurons in the cerebral cortex. Thus, the present results, together with the previous reports, suggest that most GABAergic, cholinergic and peptidergic nonpyramidal neurons in the neo- and mesocortex do not contain glutaminase.     

Drug pharmacokinetics in the obese

In the obese, modifications in body constitution (higher percentage of fat and lower percentage of lean tissue and water) can affect drug distribution in the tissues. For slightly liposoluble molecules (e.g., digoxin, antipyrine), the equilibrium distribution volume (V), total and per kilogram weight, is significantly less than that of control subjects. With lipophilic drugs (e.g., barbiturates, benzodiazepines), this parameter is significantly increased, explaining the prolongation of the plasma elimination half-life. For drugs that are almost equally soluble in water and oil (methyl xanthines, aminoglycosides), the V is slightly increased in the obese. The other main factors involved in drug diffusion in the tissues are binding to plasma and tissue proteins, and regional blood flow. In the obese the binding of drugs to albumin does not seem to be altered. A marked increase in plasma alpha-glycoprotein acid and in propranolol binding has been reported in some studies; this has not been corroborated by other authors. Although the cardiac output and total blood volume are increased in the obese, the blood flow per gram of fat is less than in nonobese subjects. This could limit diffusion in the tissues of some lipophilic drugs. Studies on hepatic clearance of drugs are not available in the obese, but hepatic histological alterations have been described. In most publications concerning drugs with biotransformation as the principal elimination route, the total plasma clearance is not reduced. Up to the present, there are no reports of any impairment involving renal elimination of drugs in the obese. Dose-adjustment of hydrophilic drugs is assessed according to the ideal weight of the individual obese subject; with lipophilic drugs the loading dose can be fixed according to the total weight; calculation of the maintenance dose depends on possible changes in the total clearance.     

Parvalbumin expression reveals a vibrissa-related pattern in rabbit SI cortex

The expression of parvalbumin-like immunoreactivity (PV-LIR) was examined in the mystacial representation within the primary somatosensory cortex (SI) of postnatal day 21 and adult rabbits. PV-LIR was expressed in a prominent vibrissa-like array of patches in layer IV despite the fact that barrels were indistinct in the cytoarchitecture. Each patch consisted of dense terminal-like PV-LIR and a preferential concentration of intensely labeled stellate neurons. Layer V contained scattered small and large intensely labeled basket cells. Layer Vb had a distinct layer of lightly labeled large pyramidal cells that received labeled basket cell terminations. Upper layer VI also contained patches of terminal-like PV-LIR that were in register with the overlying vibrissae pattern. These patches also contained a preferential distribution of labeled non-pyramidal cells as well as modified pyramidal cells. These results suggest that PV-LIR in rabbits delineates cortical modules composed of thalamorcotical afferents and inhibitory local circuits in the absence of a distinct barrel cytoarchitecure. In contrast, prior studies of rat SI cortex have revealed a distinct barrel cytoarchitecture but a uniform distribution of PV-LIR. The differences in PV-LIR between rodents and lagomorphs within the vibrissae representation in SI may be related to species differences in thalamic and local cortical circuits devoted to the whisker sense.     

小肠吸收胆固醇的分子生物学研究进展

胆固醇通过分布于十二指肠和近段空肠黏膜上皮细胞刷状缘膜的Niemann—Pick C1样蛋白1摄取，ATP结合盒G5、G8抑制小肠对胆固醇的摄取过程。进入上皮细胞的胆固醇大多数被乙酰辅酶A，胆固醇转乙酰基酶2酯化，随后通过组装形成乳糜微粒，经淋巴管进入血循环；另一部分胆固醇则以未酯化形式直接进入血循环形成高密度脂蛋白颗粒。这些过程受核受体——肝脏X受体的调控。年龄、性别、黏膜屏障和小肠传输速度也影响胆固醇的吸收。