Astroglial networks have been recently considered as emerging new therapeutic targets in CNS disorders. However, the full understanding of the complex relations between astrocytes and neurons are limited due to the lack of adequate imaging tools. Here, the present inventors propose the use of Manganese Enhanced Magnetic Resonance Imaging (MEMRI) as a new tool for evaluating in vivo the effects of modulators of astrocyte connexins, especially connexin 30 (Cx30) and connexin 43 (Cx43) inhibitors. They also propose to combine these modulators to manganese-based compounds for inducing antitumor and radiosensitizing effects.