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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 51 (1983), S. 451-462 
    ISSN: 1432-1106
    Keywords: Hamster ; Corpus Callosum ; Plasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Visual callosal, corticogeniculate and corticotectal projections were examined using autoradiography and the horseradish peroxidase (HRP) technique in normal hamsters and in animals subjected to removal of both eyes at birth. The visual callosal pathway in the bilateral enucleates was markedly abnormal. The central portion of area 17 which was, for the most part, devoid of callosal cells and terminals in the normals, contained heavy callosal labelling and a large number of callosal neurons in the enucleated animals. The laminar distribution of callosal terminals in the medial part of area 17 in the enucleates was very similar to that seen near the 17-18a border in the normal animals. Label was densest in layers V and VI, light in lamina IV, and fairly dense in the supragranular layers. The laminar distribution of callosal neurons in the bilateral enucleates was, however, quite abnormal. Callosal cells were scattered, in approximately equal proportions, throughout layers II–III and V. In the normals, over 70% of all callosal neurons were in layers II–IV. The laminar origins and topography of the corticotectal and corticogeniculate projections were essentially normal in the blinded hamsters.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Immunocytochemistry ; Serotonin ; Hamster ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Immunocytochemistry for serotonin (5-HT) was carried out in both hamsters and rats in order to determine whether or not 5-HT-positive cells existed in the superior colliculus (SC) of either species. In both hamster and rat, the superficial and deep SC laminae contained dense networks of 5-HT-positive fibers. The rat's SC contained no 5-HT-positive neurons. In hamster, numerous 5-HT-immunoreactive cells were visible throughout the depth of the stratum griseum superficiale (SGS). These neurons had a variety of morphological characteristics and included marginal cells, horizontal cells, and neurons with vertically oriented dendritic trees. No 5-HT-positive neurons were found in any other portion of the hamster's SC. 5-HT-positive SC cells were observed with antisera from two different sources and they were not seen in animals that were pretreated with reserpine. Pretreatment with fluoxetine (an inhibitor of 5-HT uptake) also resulted in a disappearance of 5-HT-positive neurons in the hamster's SC. This result indicated that “serotonergic” cells in the colliculus of this species are capable of taking up, but probably not synthesizing, this indoleamine. The dorsal and ventral lateral geniculate nuclei (LGNd and LGNv, respectively) both contain numerous 5-HT-positive fibers and both of these structures receive input from the SGS. Combination of retrograde tracing with fluorogold and immunocytochemistry indicated that 5-HT-accumulating SC neurons were not the source of these fibers. Unilateral ablation of the superficial SC laminae also failed to reduce 5-HT immunoreactivity in either the LGNd or LGNv. These results are consistent with the possibility that 5-HT-accumulating cells in the hamster's SC may be interneurons that take up this transmitter after it is released by afferents to this nucleus.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Exuberance ; Trigeminal subnucleus interpolaris ; Plasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Anterograde tracing with the carbocyanine dye, Di-I, was used to describe the normal postnatal development of the projection from the trigeminal (V) brainstem complex to the superior colliculus (SC) in hamster. In adult hamsters, this projection is completely restricted to the deep laminae, primarily the stratum album intermedium. Trigeminal fibers were present in the SC by the day of birth, and at this time, they terminated mainly in the deep layers. However, labelled fibers also extended into the superficial laminae (the stratum griseum superficiale and stratum opticum) reaching as far as the SC surface. Trigeminal projections to the superficial SC laminae were visible as late as postnatal day (P-) 6, but were absent by P-8. During the period when V axons were present in the superficial SC laminae, they could not be detected in the dorsal lateral geniculate nucleus.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 86 (1991), S. 373-383 
    ISSN: 1432-1106
    Keywords: Corticofugal projections ; Waiting periods ; Plasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Anterograde and retrograde labelling with the carbocyanine dye, Di-I, was used to assess the development of the visual cortical projection to the superior colliculus (SC) in pre- and postnatal hamsters. Posterior cortical axons arrive in the SC on postnatal (P-) day one (the first 24 hours after birth = P-0) and begin to arborize in the superficial laminae (the stratum griseum superficiale [SGS] and stratum opticum [SO]) within one day after they enter the tectum. Over succeeding days, the density of the projection increases and numerous labelled fibers are visible throughout the depth of the SGS and SO. Beginning on P-6, there is a decrease in the density of labelled fibers in the upper SGS and by P-10, the laminal distribution of the occipital corticotectal pathway appears adult-like. Anterograde tracing with Di-I also revealed the presence of a few corticotectal fibers that crossed the midline in both the SC and posterior commissures to terminate mainly in the superficial tectal laminae contralateral to the injection site. Crossed corticotectal fibers were visible in hamsters aged between P-3 and P-12. Retrograde tracing with Di-I in hamsters killed between P-3 and P-12 demonstrated that both the ipsilateral and crossed corticotectal projections arose exclusively from pyramidal cells in developing lamina V.
    Type of Medium: Electronic Resource
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