抄録
Noxious information from the skin, joints and muscles of the limbs and trunk is carried to the superficial dorsal horn, especially to the substantia gelatinosa (SG) through the fine myelinated Aδ- and unmyelinated C-afferents. SG neurons are interneurons that have different morphological and electrophysiological properties from those of the neurons in other laminae of the spinal dorsal horn and they play an important role in the modulation of the nociceptive transmission receiving inputs from primary afferent fibers. In the present study we investigated how the information from the primary afferents are processed in the spinal cord over several segmental levels, and what the SG neurons receiving excitatory and inhibitory inputs have morphological and electrophysiological characteristics by whole cell patch clamp recordings with patch pipettes filled with neurobiotin in a horizontal slice preparation of adult rat spinal cord. We found (1) that the C-afferent-mediated EPSC in the SG spreads more rostrocaudally than the Aδ-mediated EPSC, and (2) that IPSCs mediated by both Aδ- and C-afferents distribute more rostrocaudally than EPSCs, working as a feedforwad (lateral) inhibition. Furthermore, the SG neurons are classified into four cell types based on the dedritic arborization; islet cell, small islet cell, radial cell, and vertical cell types, which have characteristic inputs depending on Aδ- or C-mediated, and excitatory or inhibitory in nature. [Jpn J Physiol 55 Suppl:S14 (2005)]
