NEURONS WITH ASYMMETRICAL DENDRITIC ARBORS IN THE SUBSTANTIA-GELATINOSA OF THE RAT SPINAL-CORD

Two types of neurons were observed in the substantia gelatinosa (SG) of the rat spinal cord which exhibit wide variations in dendritic symmetry. As demonstrated with the Golgi technique, "islet" cells with short dendritic arbors and "type III stalk" cells display dendritic patterns which vary from a bipolar type arrangement with two dendritic arbors of nearly equal dimensions to a unipolar arrangement with a dendritic arbor which extends in only one direction. Examination of the morphology and dendritic development of these neurons shows that they are unique compared with other SG neurons in that they have short, longitudinal dendritic arbors which undergo maturation relatively late in the postnatal period. As is discussed, variations in dendritic symmetry are probably dependent on the location of the terminal fields of primary and/or other types of afferents which are formed earlier in development.