MORPHOLOGICAL CHARACTERIZATION OF MARGINAL (LAMINA-I) NEURONS IMMUNOREACTIVE FOR SUBSTANCE-P, ENKEPHALIN, DYNORPHIN AND GAMMA-AMINOBUTYRIC-ACID IN THE RAT SPINAL-CORD

Neurons of the rat spinal cord were immunostained for substance P, enkephalin and dynorphin in colchicine-treated animals, and for gamma-aminobutyric acid (GABA). Lamina I stained cells were classified in the four neuronal groups of our previous morphological classification of marginal cells (See Lima and Coimbra, 1986), according to their configuration in the three main anatomical planes. Most lamina I cells exhibiting substance P-immunoreactivity belonged in the group of flattened neurons. Most enkephalinergic cells were pyramidal neurons. while GABA-immunoreactive cells included all multipolar stained neurons and some fusiform neurons. Dynorphin-immunoreactive cells could be fusiform, pyramidal or flattened. The different neurochemical nature and supraspinal projection patterns are suggestive of functional specificity for each group. It is likely that each immunocytochemical subset in each cell group includes tract cells acting at their projection target and intrinsic neurons with local functional roles.