Light microscopic evidence for a substance P-containing innervation of the human nucleus basalis of Meynert

A two color histochemical/immunohistochemical method was used to demonstrate substance P and acetylcholinesterase in sections of the human nucleus basalis of Meynert (nbM). Substance P-immunoreactive terminal-like structures were found to make contact with magnocellular, acetylcholinesterase-positive perikarya and primary dendrites throughout all subdivisions of the nbM. This apparent innervation of nbM neurons was in most cases a relatively sparse one, but a small percentage of these neurons appeared to be recipients of a very heavy innervation which covered their perikarya and primary dendrites.