NADPH-DIAPHORASE IN THE DEVELOPING RAT - LOWER BRAIN-STEM AND CERVICAL SPINAL-CORD, WITH SPECIAL REFERENCE TO THE TRIGEMINO-SOLITARY COMPLEX

A previous study indicated that in adult rat, a distinctive neuronal g roup in the dorsomedial division of the subnucleus oralis of the spina l trigeminal nucleus (SpVo) and the rostrolateral part of the nucleus of the solitary tract (Sn) is stained for nicotinamide adenine dinucle otide phosphate-diaphorase (NADPH-d), and suggested that the labeled s tructures are involved with sensorimotor reflexive functions. This stu dy aimed to characterize the developmental expression of NADPH-d in Sp Vo and Sn, including other areas of the lower brainstem and cervical s pinal cord, by means of the enzyme histochemical staining technique, f rom the prenatal through the postnatal period. On embryonic day 12 (E1 2), no neurons in the brain were stained for NADPH-d, whereas blood ve ssels were stained. Labeling in the vessels was consistently present t hroughout pre- and postnatal periods but decreased with development. O n E15, labeled neurons appeared in the dorsomedial part of SpVo and th e rostrolateral part of Sn, but not in the other nuclei. The labeled n eurons in both nuclei increased in numbers drastically to E17. Postnat ally, they tended to increase gradually in Sn, but to decrease slightl y in SpVo. The cell size of labeled neurons reached a plateau at E17 i n SpVo, but at postnatal day 4 (P4) in Sn. In other nuclei on E17, lab eling appeared in the lateral paragigantocellular reticular, intermedi ate reticular, medullary reticular, pedunculopontine tegmental, and sp inal vestibular nuclei, and laminae V, VI, and X of the cervical spina l cord. On E20 and P0, labeling appeared in the dorsal column, laterod orsal tegmental, raphe obscurus, parvocellular reticular, ventral giga ntocellular reticular, and parahypoglossal nuclei, and laminae IX of t he cervical spinal cord. On P4, labeling appeared in the parabrachial and median raphe nuclei, medial and caudolateral Sn, the magnocellular zone of subnucleus caudalis of the spinal trigeminal nucleus (SpVc), and laminae III/IV of the cervical spinal cord. On P10, labeling appea red in the paratrigeminal and dorsal raphe nuclei, the superficial zon e of SpVc, and laminae I/II of the cervical spinal cord. No newly labe led neurons appeared in any nuclei after P14. The very early appearanc e of NADPH-d staining in SpVo and Sn, which precedes the appearance of NADPH-d elsewhere in the brainstem, suggests that the nitric oxide (N O)/cyclic guanosine monophosphate (cGMP) system has an important role for primitive orofacial sensorimotor reflexive functions. Furthermore, the pattern of developmental expression of NADPH-d in SpVo and Sn sug gests that the NO/cGMP system is organized in a distinct manner in dif ferent nuclei. (C) 1996 Wiley-Liss, Inc.