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Amphetamine induces excess release of striatal acetylcholine in vivo that is independent of nigrostriatal dopamine
No full textBasal forebrain grafts in the hippocampus and neocortex: regulation of acetylcholine release
No full textAcetylcholine release in the hippocampus: regulation by monoaminergic afferents as assessed by in vivo microdialysis.
No full textThe role of monoamines in the functional regulation of the septo-hippocampal cholinergic system was studied using in vivo microdialysis of acetylcholine (ACh) release in the hippocampus of awake unrestrained rats. Systemic administration of the dopamine receptor agonist apomorphine (2.0 mg/kg) resulted in a 170% increase in hippocampal ACh overflow. Similarly the catecholamine-releasing agent amphetamine (2.5 mg/kg) produced a 400% increase in ACh overflow. The effect induced by amphetamine, but not that of apomorphine, was blocked in animals pretreated with the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine (AMPT). The effect of amphetamine on ACh release was reduced by 75% after a 6-hydroxydopamine (6-OHDA) lesion of the ventral tegmental area (VTA) but was not affected by 6-OHDA lesions of the noradrenergic dorsal and ventral bundles. However, baseline ACh overflow was increased by 130% by the dorsal and ventral bundle lesions. The serotonin-releasing agent p-chloroamphetamine (2.5 mg/kg) produced a 160% increase in hippocampal ACh release, and this effect was enhanced after a 5,7-dihydroxytryptamine (5,7-DHT) lesion of the serotonin projection system. The results show that surgical or pharmacological manipulations of the ascending brainstem monoaminergic systems, which innervate wide areas of the forebrain, including the septum and the hippocampal formation, have pronounced effects on septo-hippocampal cholinergic activity. Thus, the present data provide support for the view that information regarding behavioral state and arousal is conveyed to the septo-hippocampal system via ascending monoaminergic systems
Functional activity of intrahippocampal septal grafts is regulated by catecholaminergic host afferents as studied by microdialysis of acetylcholine.
No full textPrevious microdialysis experiments have shown that acetylcholine (ACh) release from septal grafts in the hippocampus of awake rats is influenced by the behaviour of the animals, which strongly suggests that the host brain can exert a regulatory control over the activity of the grafted neurons. Since the activity of the normal septo-hippocampal cholinergic system is likely to be regulated, in part, by brainstem catecholaminergic afferents, we wished to study the effect of catecholaminergic drugs on ACh release in the hippocampus reinnervated by septal grafts. Rats were subjected to a unilateral aspirative fimbria-fornix (FF) transection and grafted with tissue from the fetal septal-diagonal band area, either as a cell suspension injection into the depth of the hippocampus or as a solid implant in the FF lesion cavity. Microdialysis of ACh release was carried out 17-20 months after transplantation in awake, freely-moving animals. The reduction in steady-state ACh overflow induced by the FF lesion (-81%) was restored to normal or above normal levels in rats with either solid or suspension grafts. In normal rats, systemic administration of apomorphine (2.0 mg/kg, s.c.) or amphetamine (2.5 mg/kg, i.p.) caused a 3.7 (+189%) or 7.8 (+301%) pmol/15 min increase in ACh overflow compared to the previous baseline level, respectively. The drug-induced increases in ACh levels in the FF-lesioned controls was substantially lower than normal (86-89% reduction). Both apomorphine and amphetamine resulted in an approximately two-fold increase in hippocampal ACh release in rats with suspension grafts. These responses were significantly increased over those seen in rats with FF lesions only, but they tended to be lower and more variable than normal. Rats with solid septal grafts responded significantly stronger than FF lesion controls to amphetamine with two-fold increased ACh overflow, whereas the response to apomorphine was less clear-cut. Pretreatment with the catecholamine synthesis blocker alpha-methyl-p-tyrosine (AMPT; 200 mg/kg x 3) did not affect steady-state or apomorphine-stimulated release of ACh in any of the groups, whereas the effect of amphetamine was abolished in both normal and grafted rats. The results suggest that ACh release derived from septal grafts in the hippocampus, similar to the normal septo-hippocampal system, can be affected by manipulations of the host catecholaminergic systems. This mechanism may, at least in part, underlie the ability of the host brain to influence and control the activity of grafted cholinergic neurons
Compensatory changes of in vivo acetylcholine and noradrenaline release in the hippocampus after partial deafferentation, as monitored by microdialysis.
No full textLesions of the fimbria-fornix pathways are known to induce a partial cholinergic and noradrenergic denervation of the hippocampal formation, which is followed by a slow and protracted collateral sprouting by the spared afferents. Using the intracerebral microdialysis technique, compensatory changes in extracellular levels of acetylcholine (ACh) and noradrenaline (NA) have been monitored over time in the partially denervated hippocampus of awake unrestrained rats subjected to an unilateral fimbria-fornix (FF) transection. One week after the lesion, baseline ACh output was reduced by 90% and 80% in the dorsal and ventral hippocampus, respectively, and it remained depressed still by 6 months after lesion. KCl-evoked and atropine-stimulated ACh efflux were equally reduced by 1 week after lesion, remained depressed at 3 months, but showed a significant recovery by 6 months post-lesion. Tissue choline acetyltransferase (ChAT) activity levels, initially reduced by 92% and 86%, in the dorsal and ventral hippocampus, respectively, recovered significantly by 3 months and remained unchanged at 6 months. Baseline NA output was significantly reduced (-80%) in the dorsal hippocampus by 1 week after the lesion and showed a partial recovery over time (to 50% of normal), whereas the ventral part was not significantly affected by the FF lesion. The significant FF lesion-induced reduction in KCl- or desipramine (DMI)-stimulated NA release observed in the dorsal hippocampus at 1 week after the lesion remained unchanged during the subsequent months. By contrast, in the ventral hippocampus, the initial 65-70% reduction in KCl- and DMI-stimulated NA release significantly recovered to normal levels within 3 months post-lesion. The NA tissue levels were significantly reduced by 4 weeks after lesion, in the dorsal hippocampus and did not show any significant recovery over time. In the ventral hippocampus, these levels were significantly reduced only at 4 weeks. Transmitter turnover, expressed as the ratio between dialysate levels and tissue ChAT or NA content, showed a 3-fold increase in the dorsal hippocampus at 4 weeks after lesion, but not at later time points. This indicates that the spared noradrenergic and cholinergic afferents respond to the partial denervation by a transient increase in transmitter turnover, evident as early as 4 weeks post-lesion in the region of maximal denervation. This was followed by a long-term increase in evoked transmitter release which may result from a slowly progressing compensatory sprouting of the spared afferents
Spatial learning impairments in rats with selective immunolesion of the forebrain cholinergic system.
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Regulation of neurotrophin and trkA, trkB and trkC tyrosine kinase receptor messenger RNA expression in kindling.
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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