Regeneration of neuronal cell types in Schmidtea mediterranea: an immunohistochemical and expression study.

Freshwater planarians are unique in their ability to regenerate a complete Central Nervous System (CNS) from almost any small piece of their body in just a few days. The planarian CNS contains a pair of anterior cephalic ganglia lying on top of two ventral nerve cords that extend along the length of the animal. Studies of planarian CNS regeneration have generally used pan-neural markers, which provide only a general overview of the process. Nevertheless, some reports have started to characterize the genes that are required for this process. In this study, to obtain a more detailed description of planarian neural regeneration, we monitored the regeneration of neuronal populations specifically labelled with antibodies against serotonin, allatostatin, neuropeptide F, GYRFamide and FMRFamide. We also characterized the regeneration of dopaminergic and octopaminergic cell populations by in situ hybridization. Finally, we characterized the expression pattern of a set of receptors for neurotransmitters, neuropeptides and hormones that are suggested to play a role in the regeneration process itself. Together, these data provide a more detailed description of the cellular events occurring during anterior and posterior CNS regeneration in planarians and provide the foundations for future mechanistic studies into the regeneration process in this important model system.