beta-Aminopropionitrile (beta APN), a peptide found in leguminous plants, is a multifunctional aminonitrile because it has some action on collagen, elastin, and nervous cells. Due to its action on the nervous system, it is very interesting to show its inhibitory effect on cultures of neurons. In the present study, we have demonstrated that beta APN can produce progressive degeneration of neurons and that this effect is dose-dependant. Neuronal cultures were prepared from 14-day-old rat embryos with a cell density of 10(4) cells/cm2 in the control plates. Progressive concentrations of beta APN (from 10(-7) M to 10(-3) M) were added and a 50 Inhibitory Dose (ID50) of 10(-5) M was found. At concentrations of 10(-5) M of beta APN, the neurons showed a loss of synapsis and thinning of neuronal prolongations. Based on the morphological changes observed, we think that beta APN may be used as a neurodegeneration model similar to that obtained with acrylamide, carbon disulfide, beta-beta'-iminodipropionitrile, or aluminum salts.