DISTRIBUTION OF NADPH-DIAPHORASE REACTIVITY IN THE SPINAL-CORD OF METAMORPHOSING AND ADULT XENOPUS-LAEVIS

The histochemical NADPH-diaphorase reaction has identified distinct ne uronal populations in the nervous system of several species. Considera ble evidence suggests that NADPH-d is a neuronal nitric oxide synthase (NOS). We examined spinal cords of adult and metamorphosing Xenopus l aevis (XL) for developmental differences in NADPH-d reactivity. In adu lt XL, labeling was found in all dorsal root ganglia (DRGs) and in the ir termination sites within the dorsal horn (cutaneous afferent field) and intermediate gray (muscle afferent field). Cell bodies in the int ermediate gray regions containing the autonomic preganglionic neurons were labeled in thoracic and sacral sections. Neurons located in the m edial (MMC) and lateral motor columns (LMC) of the ventral horn were a lso stained. In metamorphosing XL, reactivity was detected in neurons in the intermediate gray, in the MMC and in the LMC as in the adult. A dditionally, primary motoneurons including those innervating tail musc ulature were labeled. Neurons in the DRGs were stained at all stages; in the dorsal horn, the density of staining reflected the development of the sensory afferent fields. The conservation of NADPH-d reactivity in adult and metamorphosing XL spinal neurons suggests that NOS may b e involved in processes independent of developmental changes occurring in XL spinal cord.