Previously, we established that a spatially and temporally predictable pattern of spontaneous cell death occurs in pyramidal hippocampal neurons maintained in organotypic slice cultures. We have begun to examine the signalling events that may be relevant to this process by analyzing the expression of cellular immediate-early genes (cIEGs). In the present studies, organotypic hippocampal cultures were generated from transgenic rats that carry a fos-lacZ fusion gene. β-Galactosidase activity in these rats accurately recapitulates Fos expression. An association was observed between cell death, as determined by propidium iodide (PI) staining, and Fos-lacZ expression. There was a consistent rise in β-galactosidase activity in vulnerable regions 1-2 days before the peak of spontaneous neuronal death. Long-term treatment with TTX, CNQX, or D,L-APV inhibited the spontaneous neuronal death as well as Fos-lacZ expression. Furthermore, Fos-lacZ induction and cell death could be evoked by removal of these receptor antagonists or by application of the excitotoxin, kainic acid. The association between cIEG expression and cell death, shown here and by others, suggests that these genes contribute to regulatory events involved with cell death and/or protection. © 1995.