Quantification of cholinergic and select non-cholinergic mesopontine neuronal populations in the human brain

The pars compacta and pars dissipata of the pedunculopontine nucleus contai n cholinergic cell group Ch5, and the laterodorsal tegmental nucleus contai ns cholinergic cell group Ch6. The pedunculopontine nucleus has been implic ated in a variety of functions, including mediation of rapid eye movement s leep and in extrapyramidal motor function, although the role of cholinergic and non-cholinergic neurons is unclear. Quantitative neuroanatomical techn iques were used to map the distribution of cholinergic neurons in the mesop ontine nuclei of the adult human brain. In addition, the number and distrib ution of comparably sized non-cholinergic neurons at selected anatomical le vels were compared. An antibody raised against human choline acetyltransfer ase was used to stain immunohistochemically the mesopontine neurons in six brains, ranging in age from 28 to 60 years. The rostrocaudal length of the Ch5/Ch6 cell complex was approximately 10 mm. The estimated total number of cells was similar for all brains, and varied by less than 7%. The estimate d average number of cholinergic cells in the combined pedunculopontine and laterodorsal tegmental nuclei was approximately 20,000, with 30% of the cel ls in the pedunculopontine nucleus pars compacta, 57% in the pedunculoponti ne nucleus pars dissipata and 13% in the laterodorsal tegmental nucleus. Th ere was no correlation between cell number and age. Within areas of mesopon tine tegmentum occupied by the Ch5 cholinergic neurons, there were often mo re noncholinergic neurons than comparably sized cholinergic neurons. The present study provides detailed maps of the distribution and number of mesopontine cholinergic neurons in the normal human brain. Many non-choline rgic neurons are intermixed with the cholinergic pedunculopontine neurons. One region of the pedunculopontine nucleus pars dissipata containing few ch olinergic neurons, located adjacent to the ventral border of the pedunculop ontine nucleus pars compacta, may correspond to the midbrain-extrapyramidal area as defined previously in rodent and in non-human primate. These data will be useful for quantitative neuropathological studies concerning the ro le of both cholinergic and non-cholinergic mesopontine neurons in diseases proposed to affect these neurons, including Parkinson's disease, schizophre nia and progressive supranuclear palsy. (C) 1999 IBRO. Published by Elsevie r Science Ltd.