Expression of Neuronal Nitric Oxide Synthase (nNOS) in Purkinje Cells During Human and Rat Cerebellar Ontogenesis
Guethe1, L.M.; Zucchi2, F.C.R.; Neder3, L.; Chimelli4, L. and Martins5, A.R.
Department of Psychology and Education1 FFCLRP-USP; Departments of Neurology2, Pathology3 and Pharmacology5 FMRP-USP and Department of Pathology4 UFRJ
Background and purpose Nitric Oxide (NO) is a neurotransmitter/neuromodulator whose synthesis is catalyzed by nNOS. Neuronal NOS is constitutively expressed in neurons, and appears to play a role in neural development. However, the detection and involvement of nNOS in Purkinje (PU) cell ontogeny has not yet been clearly established. The changing level of nNOS expression during rat and human Purkinje cell development is reported here.
Experimental procedure Cerebella of postnatal (P) male albino Wistar rats P0-P28 and adult were paraformaldehyde-fixed and paraffin-embedded. Human cerebella [11th gestational week (GW) to 3 year-old (Y)] obtained at autopsy were formalin-fixed and paraffin-embedded. Eight mm (rat) and 5 mm (human) sections were incubated with anti-nNOS antibody. Antibody detection was done using a biotinylated swine anti-rabbit antibody and the ABC kit, with diaminebenzidine as a chromogen.
Results Changing levels of immunoreactive-like (IR) nNOS were detected throughout the ontogenesis of human and rat cerebellum. In the rat cerebellum, PU cells showed a strong nNOS IR labeling from P0-P15, decreasing thereafter until it was not detected by P28. Neuronal NOS IR was detected in both nucleus and cytoplasm of rat PU cells, and its intensity differed among cerebellar folia. In the human PU cells, nNOS staining was detected from 11GW to 3Y. PU cells exhibited a strong-to-moderate nNOS IR in nucleus and cytoplasm between 11-20GW. Nuclear staining intensity, but not the cytoplasm one, decreased from 20 to 32GW. At 34GW the PU cell layer was a single cell thick and the apical swelling showed an intense staining. In human newborns, the labeling decreased in the cytoplasm but remained strong in dendrites.
Conclusion The changing localization and levels of nNOS IR in the developing Purkinje cells is suggestive that nNOS may play a role in PU cell differentiation.
Supported by CNPq, FAPESP and FAEPA.
|