Crayfish mechanoreceptor neuron prevents photoinduced apoptosis of satellite glial cells

Interactions between neurons and glia play a key role in the development, functioning and survival of the nervous system. However, the influence of neurons on glial cells has received less attention than the role of glia in supporting neural functions. We here investigated the role of isolated crayfish stretch receptor neuron in the death of satellite glial cells under photodynamic impact. After staining with aluminum phthalocyanine photosens, the neuronal cell body was locally irradiated with a focused beam of He-Ne (633 nm, 200 W/cm2) or semiconductor laser (650 nm, 50 W/cm2). This rapidly abolished neuronal activity. The whole preparation was then subjected to total laser irradiation with lower intensity (633 nm, 0.3 W/cm2), which induced death of glial cells. Double staining of the preparation with propidium iodide and Hoechst 33342 in the following 6-7 h allowed the visualization of necrotic, apoptotic and alive cells. Previous neuron inactivation with the focused laser beam was found to increase photodynamically-induced apoptosis but not necrosis of satellite glial cells enwrapping the axon. Therefore, the intact neuronal cell body protected satellite glial cells against photoinduced apoptosis. Altogether the data indicate that mechanoreceptor neurons release some signaling molecules involved in the prevention of glial apoptosis. This may provide integrity of the stretch receptor organ and its resistance to injurious factors.