The effects of various neuroactive substances on the intracellular free Ca2+ concentration ([Ca2+]i) in cultured type-2 astrocytes were examined by fura-2-based microfluorometry. Type-2 astrocytes showed [Ca2+]i elevation in response to all the substances examined, i.e. carbachol (10(-4) M), histamine (10(-4) M), noradrenaline (10(-4) M), serotonin (10(-4) M), substance P (10(-6) M), vasopressin (10(-6) M) and glutamate (10(-4) M). Not all type-2 astrocytes, however, responded to these substances at the concentrations tested, and the percentages of astrocytes showing a Ca2+ response differed depending on the substance. These results indicate that type-2 astrocytes are potential targets for widely diverse neuroactive substances and heterogeneous in response to them.