Evidence for an anuran homologue of the mammalian spinocervicothalamic system: an in vitro tract-tracing study in Xenopus laevis.
Evidence is presented for an anuran homologue of the mammalian spinocervicothalamic system. In vitro tract-tracing experiments with biotinylated dextran amine Xenopus laevis show that ascending spinal fibres from all levels of the spinal cord, passing via the dorsolateral funiculus, terminate in a cell area ventrolateral to the dorsal column nucleus. This cell area can be considered a possible homologue of the mammalian lateral cervical nucleus. After tracer applications to the ventral thalamus or to the torus semicircularis (both targets for somatosensory projections), the anuran lateral cervical nucleus was retrogradely labelled contralateral to the application sites. Tracer applications to the dorsolateral funiculus at the obex level and rostral spinal cord resulted in labelling of the cells of origin of the spinocervical tract. These were found, mainly ipsilaterally, in the ventral part of the dorsal horn, and were rather evenly distributed throughout the spinal cord. These data suggest the presence of an anuran homologue of the mammalian spinocervicothalamic system. A brief survey of the literature shows that such a system is much more common in vertebrates than previously thought.
Muñoz
A
A
Department of Cell Biology, Universidad Complutense de Madrid, Madrid, Spain.
Muñoz
M
M
Gonzalez
A
A
ten Donkelaar
H J
HJ
D000344:Afferent Pathways / Q000033:anatomy & histology; D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives; D003911:Dextrans; D004525:Efferent Pathways / Q000033:anatomy & histology; D005456:Fluorescent Dyes; D008161:Lumbosacral Region; D008322:Mammals / Q000033:anatomy & histology*; D009333:Neck / Q000294:innervation*; D013133:Spinothalamic Tracts / Q000033:anatomy & histology*; D013909:Thorax; D014982:Xenopus laevis / Q000033:anatomy & histology*
D003911:Dextrans; D005456:Fluorescent Dyes; C076397:biotinylated dextran amine; D001710:Biotin