C1–C3 spinal cord projections to periaqueductal gray and thalamus: A quantitative retrograde tracing study in cat

• Published in: Brain research 2005-05, Vol.1043 (1), p.87-94
• Main Authors: Mouton, Leonora J., Klop, Esther Marije, Holstege, Gert
• Format: Article
• Language: English
• Subjects: Anatomy; Animals; Anterior Horn Cells - cytology; Biological and medical sciences; Cats; Central nervous system; Cervical Vertebrae; Female; Fundamental and applied biological sciences. Psychology; Lamina VI; Lamina VII; Neural Pathways; Nociception; Nociceptors - cytology; Periaqueductal Gray - cytology; Somesthesis and somesthetic pathways (proprioception, exteroception, nociception); interoception; electrolocation. Sensory receptors; Spinomesencephalic; Spinothalamic Tracts - cytology; Thalamus - cytology; Ventral horn; Vertebrates: nervous system and sense organs; Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2005.02.042

By far, the strongest spinal cord projections to periaqueductal gray (PAG) and thalamus originate from the upper three cervical segments, but their precise organization and function are not known. In the present study in cat, tracer injections in PAG or in thalamus resulted in more than 2400 labeled cells, mainly contralaterally, in the first three cervical segments (C1–C3), in a 1:4 series of sections, excluding cells in the dorsal column and lateral cervical nuclei. These cells represent about 30% of all neurons in the entire spinal cord projecting to PAG and about 45% of all spinothalamic neurons. About half of the C1–C3 PAG and C1–C3 thalamic neurons were clustered laterally in the ventral horn (C 1–3vl), bilaterally, with a slight ipsilateral preponderance. The highest numbers of C 1–3vl-PAG and C 1–3vl-thalamic cells were found in C1, with the greatest density rostrocaudally in the middle part of C1. A concept is put forward that C 1–3vl cells relay information from all levels of the cord to PAG and/or thalamus, although the processing of specific information from upper neck muscles and tendons or facet joints might also play a role.