Neuroanatomische Charakterisierung blickstabilisierender Neurone an der Hirnstammmittellinie der Primaten, einschließlich des Menschen

The aim of this project was to describe the localization and the
histological characteristics of a generally unknown group of
neurons in the brainstem of the macaque and find homologous cell
groups in man. These cells are scattered in several clusters and
are known to project to the cerebellar flocculus. Büttner-Ennever
und Büttner called them “cell groups of the paramedian tract” (PMT
cell groups). The physiological roll of these cells could lie in
the stabilization of gaze holding. 1) In this thesis the cell
groups are named consecutively PMT-1 to PMT-6 from caudal to
rostral. In an attempt to highlight these neurons, we tested them
with a battery of “markers”. The following staining procedures were
used as “markers”: • enzymatic detection of
acetylcholine-esterase(AchE) • enzymatic detection of
cytochrome-c-oxidase (COE) • cytochrome-c-oxidase
immunocytochemistry (CO) • calretinin immunocytochemistry (CR) •
calbindin immunocytochemistry (CB) • parvalbumin
immunocytochemistry (PAV) • serotonin immunocytochemistry (5-HT)
The results showed that the enzymatic detection of AchE and COE
highlighted the PMT cell groups and their neuropile most clearly in
macaque. AchE and COE were used as markers for the putative
homologous cells in man. However the PMT-6 cell group was not
identifiable in man with AchE or COE. The intensive neuropile
staining was an important feature to identify the PMT cell groups.
On the other hand the cytochrome-c-oxidase immunocytochemistry (CO)
illustrated the cytoarchitecture better. 2) After the injection of
3H-leucine into premotor regions for horizontal or vertical eye
movements in macaque monkeys, Büttner-Ennever et al. (1989)
described labeled terminals were found in PMT cell regions. In
order to check the validity of our histological markers, we
compared the results with the tract tracing results in the PMT-cell
regions. Thus the PMT neurons could be defined by their inputs from
premotor regions. There were also found to be the region with
intensive neuropil staining with AchE and COE. We were able to
distinguish the PMT neurons that mainly received horizontal
premotor inputs and others that mainly received vertical ones. 3)
The PMT neurons are localized near the midline of the brainstem
close to the raphe neurons, which are serotoninergic. This is one
reason why there are sometimes mistaken for raphe neurons (McCrea
et al., 1987a,b). By means of the immunocytochemical markers 5-HT
(macaque) and PH8 (man) we could outline the serotoninergic “raphe
neurons” and could distinguish them from the PMT neurons. In the
same way we could differentiate the motoneurons from the PMT
neurons in the abducens nucleus by highlighting the motoneurons
with the immunocytochemical marker ChAT. 4) A clear difference in
cell morphology between PMT cells and raphe cells was also found.
In both macaque and man the nucleus of PMT cellsomata were larger
and more clearly visible than in raphe neurons. Insofar as the PMT
cells in macaque could be clearly localized and also the homologue
groups in man could be found, the aim of this thesis was achieved.
Additionally we could show that the cell groups PMT-1, PMT-2,
PMT-3, PMT-4a, PMT-5a and PMT-5c are associated mainly with
vertical premotor inputs. The groups PMT-4b and PMT-5b were mainly
associated with horizontal premotor inputs. The groups PMT-4b,
PMT-5b and PMT-5c were described here for the first time and must
be verified in future studies.