Connectivity of striatal grafts implanted into the ibotenic acid-lesioned striatum--II. Cortical afferents.
Grafts of fetal striatal tissue, implanted into the ibotenic acid-lesioned caudate-putamen in adult recipient rats, have previously been shown to receive extensive afferent inputs from various subcortical areas in the host. In the present study, the formation of graft afferents from the host neocortex has been analysed, 3-12 months after transplantation, by means of the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin, iontophoretically injected at multiple sites into the host frontal cortex, in combination with intra-transplant injections of the fluorescent retrograde tracer, Fluoro-Gold. From the cortical injection sites, fibres labelled with Phaseolus vulgaris leucoagglutinin could be traced through the corpus callosum, along the myelinated fascicles of the internal capsule, into the host caudate-putamen. The labelled axons passed in large numbers across the host-graft border zone to form a rich terminal plexus that covered large parts of the grafted tissue, in close association with the grafted neurons. The labelled corticostriatal terminal network was dense, particularly in the peripheral portions of the grafts, although it did not reach the density seen in the spared portions of the host caudate-putamen. Injections of Fluoro-Gold into the depth of the striatal grafts labelled large numbers of neurons in the frontoparietal cortical regions. Consistent with previous findings, labelled neurons were also found, ipsilateral to the graft, in the intralaminar nuclear complex of the thalamus, basolateral amygdala, substantia nigra and dorsal raphe. The host neocortical neurons labelled by Fluoro-Gold injections into the graft had the same laminar and regional distribution as the neurons labelled from the homotopic area of the intact striatum, indicating that the cortical afferents to the graft were derived from those corticostriatal neurons which projected to the area of the ibotenic acid-lesioned caudate-putamen into which the graft had been placed. The number of Fluoro-Gold-labelled cortical neurons ipsilateral to the graft reached in the best cases about 1/3 of the number labelled by identical Fluoro-Gold injections into the intact caudate-putamen. Labelled neurons occurred, with a similar distribution, also in the contralateral frontoparietal cortex, but they were considerably fewer in number. The results demonstrate that fetal striatal tissue, implanted into the previously neuron-depleted adult caudate-putamen, receives innervations from all normal principal cortical and subcortical striatal afferent systems, thus pointing to a remarkable capacity of the implanted fetal striatal neurons to become anatomically integrated into the lesioned host striatal circuitry.
Wictorin
K
K
Department of Medical Cell Research, University of Lund, Sweden.
Björklund
A
A
D000818:Animals; D003342:Corpus Striatum / Q000166:cytology / Q000502:physiology / Q000637:transplantation*; D005260:Female; D005456:Fluorescent Dyes; D006085:Graft Survival; D007051:Ibotenic Acid; D009416:Nerve Regeneration; D009434:Neural Pathways; D010835:Phytohemagglutinins; D051381:Rats; D011919:Rats, Inbred Strains; D013266:Stilbamidines
C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; D005456:Fluorescent Dyes; D010835:Phytohemagglutinins; D013266:Stilbamidines; C100156:leukoagglutinins, plants; D007051:Ibotenic Acid