How mainly spinothalamic tract cells are there? A retrograde tracing study in cat

The spinothalamic tract, well known for its role in nociception, is the most frequently studied ascending pathway originating from the spinal cord. It is known that spinothalamic neurons are located in all segments of the spinal cord, but in most mammals the total number of spinothalamic neurons is not known. In three cats, after large wheat germ agglutinin-conjugated horseradish peroxidase injections involving all parts (one case) or almost all parts of the thalamus (two cases), the number of retrogradely labeled profiles was counted in a 1:4 series of sections of all spinal segments from C I to Coc2. After applying the correction factor of Abercrombie (Anat. Rec. 94 (1946) 239), it appears that a total of 12,000 cells in the spinal cord project to the thalamus. (C) 2004 Elsevier Ireland Ltd. All rights reserved.