Neurotensin immunoreactivity in the superficial laminae of the dorsal horn of the rat: I. Light microscopic studies of cell bodies and proximal dendrites.

Although neurotensin perikarya have been identified in the superficial laminae of the dorsal horn, little is known regarding the cytoarchitecture of these neurotensin-containing neurons. Immunohistochemical staining of 75-microns sections in several planes through colchicine-treated rat spinal cords revealed morphologic features of neurotensinlike immunoreactive (NLI) perikarya and proximal dendrites. Populations of NLI neurons were identified in the outer one-third of lamina II, the inner one-third of lamina II, and outer lamina III. The NLI neurons in lamina II had elongated perikarya and the dendrites emerged from the rostral and caudal poles of the cell body. The proximal dendrites of NLI cells in inner laminae II were shorter and contained more spines than outer lamina II NLI cells. The NLI cells in outer lamina III did not exhibit polarity and the proximal dendrites were generally shorter than those of NLI cells in lamina II. The lamina II cells appear similar to islet cells (Gobel, '75), while the lamina III cells have many of the characteristics of the II/III border cell described by Gobel ('78). Interestingly, the inner lamina II NLI cells occurred in clusters with NLI cells in outer lamina III. The periodicity of these clusters suggests a neurochemical dimension for the organization of the superficial laminae of the dorsal horn.