Péter Szocsics1, Péter Papp2, László Havas3, Zsófia Maglóczky1,2
1 Human Brain Research Laboratory, Institute of Experimental Medicine, HAS, Budapest
2 Laboratory of Cerebral Cortex, Institute of Experimental Medicine, HAS, Budapest
3 Szt. Borbála Hospital, Dpt. of Pathology, Tatabánya
Introduction: Numerous researchers have investigated the largest neurons in the central nervous system: the giant motoneurons of the primary motor cortex since 1874 – the first description by Vladimir Betz. Despite this fact, some features (e.g. neurochemical characteristics of the cells and its inputs) have not been described in human post mortem samples. We can find controversies in the literature of this field, too, although numerous neurological diseases are associated to motor impairment.
Aims: Therefore, our aim is to study the characteristics of the giant motoneurons and its perisomatic inputs using immunohistochemical methods in control post mortem human samples.
Method: The primary motor cortices of eight subjects without known neurological damage were investigated in both hemispheres. The brains were perfusion fixed with Zamboni solution shortly (2-5 hours) after death. The samples are originating from the middle part of the primary motor cortex (Brodmann’s area 4, corresponding the hand area in the motor homunculus). We used SMI32 (labelling non-phosphorylated neurofilaments) and parvalbumin (known to label perisomatic inhibitory cells) DAB and fluorescent immunolabelling to investigate the cells’ soma, and vesicular transporters to characterize the perisomatic terminals. We used electron microscopy to check the synapses.
Results: SMI32 antibody labelled all of the Betz cells, and the neurons showed a moderate variability in size and density among samples. Soma size and density were not influenced by gender, age or post mortem interval. Approximately 60% of giant motoneurons were immunostained for parvalbumin, too. Using electron microscopy, we find perisomatic synapses with mixed morphology. According to additional immunofluorescent investigations the terminals may have a subcortical origin.
Conclusion: Giant motoneurons differ in many features from the surrounding pyramidal cells supporting the idea, that these neurons have a special role in regulating of movements. Special features may facilitate greater and faster response of these cells to outer stimuli.
Doctoral School: János Szentágothai Neurosciences
Program: Neuromorphology and Cell Biology
Supervisor: Zsófia Maglóczky