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Buresch, Norbert (2005): Neuroanatomische Charakterisierung blickstabilisierender Neurone an der Hirnstammmittellinie der Primaten, einschließlich des Menschen. Dissertation, LMU München: Medizinische Fakultät



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.