Lanceolin and stenodactylin, new type 2 ribosome-inactivating proteins (RIPs) from Adenia plants were recently isolated and their high cytotoxicity was described. Present experiments were performed to investigate the effect of these toxins on neural cells in culture and their in vivo retrograde transport and neurotoxicity in the central nervous system. The concentrations of lanceolin and stenodactylin inhibiting by 50% protein synthesis were in the 10(-11) and 10(-12) (cerebellar granule neurons), 10(-12) and 10(-13) (astrocytes), and 10(-13) (microglia) molar range, respectively. Both RIPs resulted toxic for glial cells in culture by MTT test, killing 50% of microglia, the most sensitive cell type, at concentrations around 10(-14)M. Stenodactylin was highly neurotoxic in vivo, when injected intracerebrally, and was retrogradely transported through axons projecting to the injected region. Stereotaxic injection of 1.3 ng toxin into the left dorsal hippocampus resulted in loss of cholinergic neurons in the ipsilateral medial septal nucleus, where cell bodies of neurons providing cholinergic input to the hippocampus are located. The retrograde transport of RIPs along neurons allows to perform experiments of target-selective lesioning, and can be exploited also to perform specific experiments of immunolesioning of selected neuronal populations.