Studies on the role of the serotonin and NMDA receptors in the plasticity of the developing brain

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Distributions of nitric oxide synthase (NOS) neurons and serotonin (5-hidroxytyptamine, 5-HT) were compared throughout the mouse brain using NADPH-d histochemistry and 5-HT immunohistochemistry. The areas where NADPH-diaphorase (NADPH-d) and 5-HT positive cell bodies and fibers were much concentrated together included the medial part of the anterior olfactory nucleus, the medial septal nucleus, the diagonal band of Broca, the medial forebrain bundle, the supraependymal plexus of the ventricles, the ventrolateral geniculate nucleus, the dorsomedial subnucleus of the interpeduncular nucleus, the raphe magnus nucleus, the raphe obscurus nucleus, the dorsal raphe nucleus, the ambiguus nucleus, the solitary tract nucleus and the dorsal motor nucleus of the vagus.We examined changes in 5-HT neurons in pyrithiamine-induced thiamine deficiency in mice immunohistochemically. Extensive decreases in the densities of 5-HT-immunoreactive fibers were detected in the lateral septal nucleus, the thala … More mus, the medial mammillary nucleus, the dorsal and the median raphe nuclei, the raphe obscurus nucleus, the tegmental area, the cerebellum and the vestibular nucleus, though only a small decrease was detected in the inferior colliculus. Most remarkably, degenerative winding fibers were detected between the deep mecencephalic nucleus and the ventral tegmental area. Increases in intensity of 5-HT immunoreactivity in the dorsal raphe nucleus and decreases in the number of 5-HT-immunoreactive cell bodies in the dorsal and the median raphe nuclei were detected. These results suggest the differential vulnerability of 5-HT neurons in thiamine-deficient mice.Changes in NOS neurons in thiamine-deficient mice were also examined histochemically using NADPH-d, an identical marker for NOS containing neurons. Decreases in the number of cell bodies and the densities of fibers in NADPH-d- containing neurons were detected in particular areas of the thalamus, the lateral habenular nucleus, the dorsal raphe nucleus and the medial vestibular nucleus, and decreases in the density of the fibers was detected also in the caudal part of the medial portion of the medial mammillary nucleus in thiamine-deficient mice. A marked loss of NADPH-d-containing neurons was also detected in the hippocampus. The results suggest the possibility that the influence of NOS includes some neuropathological vulnerability of the brain to NOS in experimental thiamine deficiency. Less