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  • 1
    ISSN: 1432-1106
    Keywords: Basal ganglia ; Acetylcholinesterase ; Retrograde transport methods ; Compartmentalization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The distribution of neurons giving rise to striatal efferent projections has been studied in the cat by the aid of Mesulam's histochemical methods following large injections of horseradish peroxidase into the pallidum and substantia nigra. The findings suggest that neurons of medium size form a major fraction of the efferent neurons of the striatum and that these neurons are grouped into geometrically complex, three-dimensional networks.
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  • 2
    ISSN: 1432-1106
    Keywords: Striatonigral fibers ; Nigrostriatal projection ; Histochemistry, Primate ; Substantia nigrapars compacta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A marked histochemical compartmentalization is visible in the substantia nigra of the squirrel monkey in sections stained for acetylcholinesterase (AChE). In nigral regions containing tyrosine hydroxylase-positive neurons, there are AChE-poor and AChE-rich zones, and many of the AChE-poor zones have the form of narrow fingers extending ventrally into an AChE-rich matrix (Jimenez-Castellanos and Graybiel 1987b). The study reported here was carried out to determine whether this histochemical heterogeneity of the primate's substantia nigra is related to the known differentiation within its pars compacta of subdivisions projecting respectively to the caudate nucleus and to the putamen. Retrograde and anterograde labeling in the substantia nigra was elicited by tracer injections placed in the caudate nucleus or putamen and was plotted in relation to patterns of AChE staining and tyrosine hydroxylase immunostaining. Much of the labeling observed was organized according to borders visible with AChE histochemistry: labeled nigral neurons (and afferent fibers) tended to be clustered precisely within the AChE-poor ventrally-extending fingers or to be situated outside these zones. However, projection neurons in these ventrally-extending fingers were not exclusively related either to the caudate nucleus or to the putamen. After injections in the caudate nucleus, labeled neurons were predominantly in the AChE-poor fingers in some cases, but predominantly in AChE-rich nigral zones outside them in other cases. Labeling in and out of the ventrally-extending fingers, and along the edges of the fingers, also occurred following different tracer injections in the putamen. These findings confirm the independent clustering of nigrostriatal neurons projecting respectively to the caudate nucleus and to the putamen. The plan of nigrostriatal connections additionally appears concordant with the histochemical compartmentalization of the substantia nigra that can be detected with acetylthiocholinesterase histochemistry.
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  • 3
    ISSN: 1432-1106
    Keywords: Neural grafts ; Striatum ; Cocaine ; Immediate-early gene ; c-fos ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cocaine, a catecholamine agonist, has been shown to produce a transient induction of the immediate-early gene c-fos and its protein product Fos in the striatum of normal rats. In the present study we report that the expression of Fos can be induced by cocaine challenge in intrastriatal grafts derived from cell suspensions of embryonic striatal primordia. Fos-like immunoreactivity in the nuclei of grafted neurons was detected 2 hr after the injection of 50 mg/kg cocaine into the host rats. Neurons with Fos-immunoreactive nuclei tended to form clusters in the striatal grafts. The Fos-rich clusters were aligned with acetylcholinesterase (AChE)-rich and tyrosine hydroxylase (TH)-rich patches demonstrated in adjoining sections. Previous studies have shown that presynaptic and postsynaptic cellular markers of the dopaminergic system in the striatum, including immunostaining for TH and dopamine- and adenosine 3′:5′-monophosphate-regulated phosphoprotein (DARPP-32), and binding for high affinity dopamine uptake sites and for dopamine D1 and D2 receptor sites, are all concentrated in the AChE-rich patch regions (P regions) of such embryonic striatal grafts. The preferential expression of Fos in neurons of the P regions of the grafts thus implies that the induction of Fos was cell-type specific in being concentrated in the parts of the grafts that express striatal phenotype and that are innervated by catecholamine-containing fibers. This specificity strongly suggests that the activation of Fos expression in neurons of the P regions of the grafts reflects dopaminergic interactions between the grafts and host nigrostriatal fibers. We conclude that the cellular messenger systems and transcriptional activation mechanisms responsive to dopaminergic stimulation by the host can be activated in the embryonic striatal grafts, and that the grafts are thus functionally integrated into the host brain at the level of cellular signaling systems.
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  • 4
    ISSN: 1432-1106
    Keywords: Parabolic flight ; Postural and visual illusions ; Muscle spindles ; Sensory-motor calibration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Illusions of self motion and aircraft motion are experienced when executing deep knee bends in the high force phases of parabolic flight. The occurrence of such illusions indicates that skeletomotor control is actively calibrated to a 1 g reference level and that departures from this level affect the execution and appreciation of voluntary movements. The origin of the illusory patterns is shown to be understandable in terms of “mismatches” between efferent control signals and expected patterns of associated muscle spindle activity. It is shown, too, that spindle activity is interpreted within an entire context of spatial information about ongoing and intended motion of the body and whether the body is laden.
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  • 5
    ISSN: 1432-1106
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 6
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Saccades ; Acetylcholinesterase ; Eye movements ; Primate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The locations of saccade-related neurons were studied in the superior colliculi of two adult rhesus monkeys (Macaco, mulatta) by placing marking lesions at the sites of physiologically characterized cells and comparing these histologically identified sites with the collicular laminae and acetylcholinesterase (AChE)-rich patches. Three major conclusions were drawn on the basis of 39 histologically identified sites at which saccade-related neurons were recorded. First, saccade-related neurons were distributed from the ventral half of the optic layer through the deep gray layer, and were most concentrated in the intermediate gray and white layers. Second, there was a clear relationship between the discharge characteristics of these saccade-related neurons and the depths at which they were found. Neurons having presaccadic bursts, defined as clipped and partially-clipped, tended to be encountered more dorsally, and neurons that did not have bursts (undipped) were encountered more ventrally. Although cells having different discharge characteristics seemed to be organized along a dorsoventral axis, there was no compelling evidence that these properties were specified by their laminar locations. Third, there was no clear correlation between the locations of saccade-related neurons and the distribution of individual AChE-rich patches. Saccade-related cells were found both in the caudal superior colliculus where patches were located and in the rostral superior colliculus where patches were not found; both within and between the two tiers of AChE-rich patches in the caudal superior colliculus; and both within and between individual AChE-rich patches. However, the depth-level at which saccade-related neurons occurred generally matched the region bounded by the two tiers of AChE-rich patches in the intermediate and deep layers, and the dorsal and ventral extent of saccade-related neurons was the same as that of the AChE-rich patches.
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  • 7
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Lateral posterior nucleus ; Acetylcholinesterase ; Parabigeminal nucleus ; Pulvinar ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The superficial layers of the cat's superior colliculus innervate the medial subdivision of the thalamic lateral posterior nucleus (LPm). LPm is set off from adjoining thalamic zones by its denser staining for acetylcholinesterase (AChE). We sought to learn whether the tectal afferents to LPm might themselves be the source of the enzyme staining by examining the effects of collicular lesions on the thalamic staining pattern. Large excitotoxin lesions of the colliculus largely eliminated AChE staining in the ipsilateral LPm. By contrast, fibersparing lesions of LPm itself left AChE staining nearly unchanged. Destruction of collicular neurons by excitotoxins dramatically reduced AChE staining in fibers of the brachium and superficial gray layer of the superior colliculus. The reduction was especially pronounced in the lower part of the superficial gray layer, in which LP-projecting collicular neurons are located. These results are consistent with the view that LP-projecting collicular neurons synthesize AChE and account for much of the histochemically detectable enzyme present both in the lower superficial gray layer and in LPm. In the colliculus, the excitotoxin lesions spared AChE staining in a thin sheet at the upper border of the superficial gray layer and in the enzyme-positive patches in the intermediate layers. This surviving tectal AChE thus is probably presynaptic and could be contained at least partly in cholinergic afferents from the parabigeminal nucleus and pontomesencephalic tegmentum. The collicular lesions had no obvious effect on AChE staining in the parabigeminal nucleus or in the C-laminae or ventral division of the lateral geniculate nucleus.
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The activity-regulated, cytoskeletal-associated gene, arc, is a brain-enriched immediate-early gene whose expression is rapidly induced in the striatum by dopamine receptor agonists. This rapid induction of arc in the striatum is similar to that of other early response genes such as c-fos, junB, ▵fosB, fra, and NGFI-A, which code for transcription factors. Unlike these proteins, however, Arc is a cytoskeletal protein expressed not only in the nucleus of neurons but also in their dendrites. We investigated the patterns of Arc expression evoked in the rat striatum by acute exposures to two psychomotor stimulants, cocaine and amphetamine. Cocaine induced arc in striatal neurons that were broadly distributed within both striosome and matrix compartments of the caudoputamen. Amphetamine also evoked Arc expression in striatal projection neurons, but these were heavily concentrated in the striosomal compartment and only sparsely in the matrix compartment in the rostral striatum. The contrasting patterns of Arc expression evoked by cocaine and amphetamine parallel those of c-Fos, JunB, FRA, and NGFI-A expression induced by these two psychomotor stimulants. This difference in the action of cocaine and amphetamine at the level of protein expression may be linked to the different effects of these psychomotor stimulants on behavior.
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: To test for the relative contributions of the dopaminergicand serotoninergic systems in the striatum to the effects ofd-fenfluramine, an indirect serotonin receptor agonist, we assessedthe expression of Fos/Jun proteins induced by d-fenfluramine givenalone or in the presence of dopaminergic or serotoninergic agents. Todetermine the neuronal targets of d-fenfluramine in the striatum, weidentified the phenotypes of striatal neurons in which d-fenfluramineinduced Fos expression. Our results demonstrated that d-fenfluramineevokes nuclear expression of Fos/Jun B proteins in the striatum, and that theFos expression was dose-dependent and accompanied by transient induction ofc-fos mRNA. Fos expression was blocked byp-chloroamphetamine, a serotoninergic neurotoxin. Pretreatment withSCH 23390, a D1-dopamine receptor antagonist, led to a markeddecrease in Fos/Jun B expression in the caudoputamen, but not in the cortex,whereas pretreatment with methiothepin, a nonselective serotonin5-HT1 receptor antagonist, blocked Fos expression completely in thecortex and only partially in the caudoputamen. The expression of Fos/Jun B inthe striatum occurred mainly in dynorphin-containing neurons and in asubpopulation of striatal interneurons that exhibited NADPH-diaphoraseactivity. Most of the enkephalin-containing neurons of the striatum did notshow Fos/Jun B staining. These results suggest that the mechanism by whichd-fenfluramine induces c-fos and jun B expression in the rat caudoputamen depends at least in part on activation of the dopaminergic system by serotonin.
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  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Learning to perform a behavioural procedure as a well-ingrained habit requires extensive repetition of the behavioural sequence, and learning not to perform such behaviours is notoriously difficult. Yet regaining a habit can occur quickly, with even one or a few exposures to cues previously ...
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