Co-localization of nitric oxide synthase and NGF receptor in neurons in the medial septal and diagonal band nuclei of the rat

The relationship of neurons that express nitric oxide synthase type I (NOS-I), the synthetic enzyme of the free radical nitric oxide (NO), with cells that contain the low affinity p75 nerve growth factor receptor (NGFr) was examined in the basal forebrain region of the rat using double immunohistofluorescence. NOS and NGFr were found to be co-localized in a neuronal population that displayed a selective distribution. Double immunopositive neurons were evident in the medial septum and in rostral levels of the diagonal band nuclei where the vast majority (more than 80%) of NOS-immunoreactive cells were also NGFr-positive; the two cell populations were separate at more caudal levels of the basal forebrain. These findings support the chemical heterogeneity of septal and basal forebrain neurons which contain NGFr and indicate that in the rat a subset of neurons of the septum-diagonal band complex may release NO.