PubMed · 510611
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R Khellon. 1979. [Information processing in thermosensitive pathways].. https://pubmed.ncbi.nlm.nih.gov/510611/
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The primary objective of the present study is to demonstrate the presence of a projection to the superficial layers of the superior colliculus (SC) from the perihypoglossal nuclei, specifically from the nucleus intercalatus (INT) in the cat. Iontophoretic application of WGA-HRP into the perihypoglossal complex produced orthogradely labeled terminals in the SC contralaterally forming two bands: one is in the superficial gray layer, and the other in the intermediate gray layer. The superficial band was evenly distributed in the upper portion of the superficial gray layers (layers II1-2) and the deeper band existed in the intermediate gray layer (layer IV) being arranged in a discontinuous manner. Injections of the tracer into the superficial layers of the SC yielded retrogradely labeled cells only in the rostral part of the contralateral INT; by contrast, the injection confined to the deep layers produced labeling of cells exclusively in the nucleus prepositus hypoglossi (PH). Thus, the INT and the PH each project separately to the functionally different superficial and intermediate layers of the SC, respectively. On the basis of the present anatomical findings, it is suggested that the perihypoglossal nuclei as a whole contribute not only to the oculomotor but also to the visuosensory regulatory function in the SC.
Stimulation of hairy skin afferent fibers and/or direct depolarizing current injection initiates persistent changes in membrane potential (slow potentials), lasting up to 1 min or longer, in some deep dorsal horn neurons. Intracellular staining with horseradish peroxidase shows that these cells are interneurons, suggesting that slow potentials modulate moment-to-moment impulse transmission in local spinal circuits.
A dense plexus of fibers in the substantia gelatinosa contains nitric oxide synthase (NOS). Using electron microscopic double-labeling immunocytochemistry for NOS combined with GABA or glutamate, we find that all NOS-positive terminals in this region also contain GABA but are not enriched in glutamate. In an attempt to verify that NOS-positive terminals do not originate from primary afferents, we combined NOS immunocytochemistry with anterograde tracing from the sciatic nerve. An intrinsic spinal origin for the NOS-positive plexus is suggested. The results are discussed in the light of the possible involvement of nitric oxide in hyperalgesia.