Differential spread of afterdischarge activity initiated electrically in ventral and dorsal parts of the hippocampal formation was studied by the [14C]deoxyglucose technique in rats. Afterdischarges initiated in either the ventral or dorsal hippocampal formation, without activation of the ventral subicular cortex, increased glucose utilization in the lateral septum. In contrast, afterdischarges initiated by direct activation of the ventral subicular cortex increased glucose utilization in extensive areas of the ipsilateral amygdala, claustrum, hypothalamus, preoptic region, and basal forebrain.