Neuronal nitric oxide synthase (bNOS) messenger RNA and protein expression in developing rat brainstem nuclei

Neuronal nitric oxide synthase (bNOS) messenger RNA expression and immunoreactivity were mapped in series of cryosections through the developing rat brainstem nuclei. Between embryonic day E16 and postnatal day P16, brainstem nuclei expressed both bNOS messenger RNA (mRNA) in situ hybridization signals and protein immunoreactivity. However, NOS mRNA signals were absent from the Edinger Westphal, facial or motory trigeminal nucleus. Strong patterns of mRNA signals and immunoreactivity occurred in neurons located in the substantia nigra pars compacta and the laterodorsal tegmental nuclei. Between E24 and P16, altered patterns of bNOS mRNA positive and immunoreactive neurons, e.g. superior and inferior colliculi, raphe nuclei, solitary tract or pontine nucleus were documented. Altered NOS expression patterns thus may reflect developmental processes within distinct neuronal populations such as cell phenotype discrimination or synaptogenesis within efferent or afferent brainstem pathways. The NOS/NO system therefore appears to be a modulator for intra-/intercellular adjustment processes in normal development.