Photodynamic therapy (PDT) inhibited and irreversibly abolished firing, caused necrosis of neurons, necrosis,
apoptosis and proliferation of glial cells in the isolated crayfish stretch receptor. The role in these processes of the
central components of Ca2+-mediated signaling pathway: phospholipase C, calmodulin, calmodulin-dependent kinase
II, and protein kinase C was studied using their inhibitors: ET-18, fluphenazine, KN-93, or staurosporine, respectively.
ET-18 reduced functional inactivation of neurons, necrosis and apoptosis of glial cells. Fluphenazine and KN-93
reduced PDT-induced necrosis of neurons and glial cells. Staurosporine enhanced PDT-induced glial apoptosis. PDTinduced
gliosis was prevented by KN-93 and staurosporine. Therefore, phospholipase C participated in neuron
inactivation and glial necrosis and apoptosis. Calmodulin and calmodulin-dependent kinase II were involved in PDT-induced
necrosis of neurons and glial cells but not in glial apoptosis. Protein kinase C protected glia from apoptosis
and participated in PDT-induced gliosis and loss of neuronal activity. These data may be used for modulation of PDT
of brain tumors.