gms | German Medical Science

Objective: Calcium ions play important roles in both neuronal plasticity of regenerating nerves and neuronal cell death after nerve lesion. Oral nimodipine is recommended to reduce delayed ischemic neurological deficits related to aneurysmal subarachnoid hemorrhage (SAH). In addition, animal experiments and clinical trails revealed a beneficial effect of nimodipine for the regeneration of cranial nerves following vestibular schwannoma, laryngeal and maxillofacial surgery. Hence, we wanted to investigate the regenerative potential of nimodipine alone and in combination with the nerve growth factor (NGF) on the fibre growth of dopaminergic neurons in an in vivo like context. Furthermore, for a better understanding of the mode of action of nimodipine, gene expression analysis was carried out after nimodipine application using microarrays and real-time-PCR.

Method: We employed an organotypic brain slice co-culture model consisting of the ventral tegmental area/substantia nigra (VTA/SN) and the prefrontal cortex (PFC) from neonatal rat brains in combination with biocytin tracing and image analysis. This procedure allowed us to reconstruct the mesocortical dopaminergic system and to characterise the fibre density in the border region between VTA/SN and the target PFC after nimodipine treatment in an automated manner. Moreover, genes identified by the microarray-study were verified and quantitatively analysed with the help of real-time-PCR.

Results: The analysis revealed an enhancement of fibre growth in the border region after nimodipin treatment. Among the tested nimodipine concentrations 1 µM has been shown to have the strongest effect. This significant effect (compared to control) was increased by co-treatment with nimodipine and NGF. Analysis of lactate dehydrogenase release into the culture medium showed no significant changes, excluding toxicological effects of applied nimodipine concentrations. The microarray revealed considerable changes in gene expression induced by nimodipine.

Conclusions: Since the dopaminergic projections are cut during preparation and the developing fibre projections strongly correlate with the growth of physiological neuronal circuits, the co-cultures present both a model of regeneration and generation, convenient to analyse neuronal fibre growth. Moreover we observed a fibre growth promoting effect of nimodipine treatment. It has to be investigated if the observed nimodipine effects in our model are transferable to the human system.