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A quantitative study of spinothalamic neurons in laminae I, III, and IV in lumbar and cervical segments of the rat spinal cord.

Al-Khater KM, Kerr R, Todd AJ - J. Comp. Neurol. (2008)

Bottom Line: Our results suggest that there are 90 lamina I spinothalamic neurons per side in C7 and 15 in L4 and that some of those in C7 only project to PoT.We found that 85% of the lamina III/IV NK1r-immunoreactive neurons in C6 and 17% of those in L5 belong to the spinothalamic tract, and these apparently project exclusively to the caudal thalamus, including PoT.Because PoT projects to second somatosensory and insular cortices, our results suggest that these are major targets for information conveyed by both these populations of spinothalamic neurons.

View Article: PubMed Central - PubMed

Affiliation: Spinal Cord Group, Institute of Biomedical & Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom. a.todd@bio.gla.ac.uk

ABSTRACT
The major ascending outputs from superficial spinal dorsal horn consist of projection neurons in lamina I, together with neurons in laminae III-IV that express the neurokinin 1 receptor (NK1r) and have dendrites that enter the superficial laminae. Some neurons in each of these populations belong to the spinothalamic tract, which conveys nociceptive information via the thalamus to cortical areas involved in pain. A projection from the cervical superficial dorsal horn to the posterior triangular nucleus (PoT) has recently been identified. PoT is at the caudal end of the thalamus and was not included in injection sites in many previous retrograde tracing studies. We have injected various tracers (cholera toxin B subunit, Fluoro-Gold, and fluorescent latex microspheres) into the thalamus to estimate the number of spinothalamic neurons in each of these two populations, and to investigate their projection targets. Most lamina I and lamina III/IV NK1r-immunoreactive spinothalamic neurons in cervical and lumbar segments could be labeled from injections centered on PoT. Our results suggest that there are 90 lamina I spinothalamic neurons per side in C7 and 15 in L4 and that some of those in C7 only project to PoT. We found that 85% of the lamina III/IV NK1r-immunoreactive neurons in C6 and 17% of those in L5 belong to the spinothalamic tract, and these apparently project exclusively to the caudal thalamus, including PoT. Because PoT projects to second somatosensory and insular cortices, our results suggest that these are major targets for information conveyed by both these populations of spinothalamic neurons.

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Injection sites for experiments DI1–DI7. Drawings show the spread of Fluoro-Gold (light shading) and CTb (dark shading) in these experiments. Each vertical column represents a single experiment, and the experiment number (corresponding to those in Tables 1, 4, and 7) is shown at the bottom of the column. Numbers at the top left of each drawing give the approximate position of the section anterior to the interaural plane. Drawings are based on those in Paxinos and Watson (2005). For labeling of structures shown within these drawings, see Figure 1.
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fig03: Injection sites for experiments DI1–DI7. Drawings show the spread of Fluoro-Gold (light shading) and CTb (dark shading) in these experiments. Each vertical column represents a single experiment, and the experiment number (corresponding to those in Tables 1, 4, and 7) is shown at the bottom of the column. Numbers at the top left of each drawing give the approximate position of the section anterior to the interaural plane. Drawings are based on those in Paxinos and Watson (2005). For labeling of structures shown within these drawings, see Figure 1.

Mentions: The spread of tracer within the thalamus in each of these experiments is illustrated in Figures 1–3, and representative photomicrographs of injection sites are shown in Figure 4.Figure 1


A quantitative study of spinothalamic neurons in laminae I, III, and IV in lumbar and cervical segments of the rat spinal cord.

Al-Khater KM, Kerr R, Todd AJ - J. Comp. Neurol. (2008)

Injection sites for experiments DI1–DI7. Drawings show the spread of Fluoro-Gold (light shading) and CTb (dark shading) in these experiments. Each vertical column represents a single experiment, and the experiment number (corresponding to those in Tables 1, 4, and 7) is shown at the bottom of the column. Numbers at the top left of each drawing give the approximate position of the section anterior to the interaural plane. Drawings are based on those in Paxinos and Watson (2005). For labeling of structures shown within these drawings, see Figure 1.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2658017&req=5

fig03: Injection sites for experiments DI1–DI7. Drawings show the spread of Fluoro-Gold (light shading) and CTb (dark shading) in these experiments. Each vertical column represents a single experiment, and the experiment number (corresponding to those in Tables 1, 4, and 7) is shown at the bottom of the column. Numbers at the top left of each drawing give the approximate position of the section anterior to the interaural plane. Drawings are based on those in Paxinos and Watson (2005). For labeling of structures shown within these drawings, see Figure 1.
Mentions: The spread of tracer within the thalamus in each of these experiments is illustrated in Figures 1–3, and representative photomicrographs of injection sites are shown in Figure 4.Figure 1

Bottom Line: Our results suggest that there are 90 lamina I spinothalamic neurons per side in C7 and 15 in L4 and that some of those in C7 only project to PoT.We found that 85% of the lamina III/IV NK1r-immunoreactive neurons in C6 and 17% of those in L5 belong to the spinothalamic tract, and these apparently project exclusively to the caudal thalamus, including PoT.Because PoT projects to second somatosensory and insular cortices, our results suggest that these are major targets for information conveyed by both these populations of spinothalamic neurons.

View Article: PubMed Central - PubMed

Affiliation: Spinal Cord Group, Institute of Biomedical & Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom. a.todd@bio.gla.ac.uk

ABSTRACT
The major ascending outputs from superficial spinal dorsal horn consist of projection neurons in lamina I, together with neurons in laminae III-IV that express the neurokinin 1 receptor (NK1r) and have dendrites that enter the superficial laminae. Some neurons in each of these populations belong to the spinothalamic tract, which conveys nociceptive information via the thalamus to cortical areas involved in pain. A projection from the cervical superficial dorsal horn to the posterior triangular nucleus (PoT) has recently been identified. PoT is at the caudal end of the thalamus and was not included in injection sites in many previous retrograde tracing studies. We have injected various tracers (cholera toxin B subunit, Fluoro-Gold, and fluorescent latex microspheres) into the thalamus to estimate the number of spinothalamic neurons in each of these two populations, and to investigate their projection targets. Most lamina I and lamina III/IV NK1r-immunoreactive spinothalamic neurons in cervical and lumbar segments could be labeled from injections centered on PoT. Our results suggest that there are 90 lamina I spinothalamic neurons per side in C7 and 15 in L4 and that some of those in C7 only project to PoT. We found that 85% of the lamina III/IV NK1r-immunoreactive neurons in C6 and 17% of those in L5 belong to the spinothalamic tract, and these apparently project exclusively to the caudal thalamus, including PoT. Because PoT projects to second somatosensory and insular cortices, our results suggest that these are major targets for information conveyed by both these populations of spinothalamic neurons.

Show MeSH
Related in: MedlinePlus