The identification of some sources of afferent input to the rat nucleus basalis magnocellularis by retrograde transport of horseradish peroxidase.

Neurons of the nucleus basalis magnocellularis (NBm) of the rat are contained within the ventromedial globus pallidus and adjacent internal capsule. Horseradish peroxidase injection limited to the ventromedial globus pallidus result in sparse neuronal labeling in a variety of brainstem, thalamic and hypothalamic nuclei, and the basal nuclei identified after NBm injections. Thus, these contiguous regions have comparable subcortical inputs. By contrast, only NBm injections yielded a large number of labeled neurons in layer V of NBm cholinergic neurons. in addition to the reciprocity observed between NBm and frontal cortex, the ventral tegmental area and NBm likewise appear to be reciprocally connected.