The long-term effects of a single injection of beta,beta'-iminodipropionitrile on slow axonal transport in the rat.

Following a single intraperitoneal injection of beta,beta'-iminodipropionitrile (IDPN) simultaneously with or 5 weeks after injection of [35S]methionine into the ventral horn area of rat spinal cord, the changes of slowly migrating axonal proteins were analyzed electrophoretically up to 10 weeks after labeling, and the following results were obtained. After a single injection of IDPN, only the transport of neurofilament proteins is inhibited, leaving that of tubulin and actin almost unaffected, though a small portion of the former was retarded through the interaction with neurofilaments. The inhibitory effect of IDPN on neurofilament transport is not a complete blockage, but a slowing of the rate of transport to about a half of the control with a possible short halting period just after IDPN treatment. The dose-response data indicate a threshold between 0.5 and 1.0 g/kg of body weight, increasing the dose above which does not further affect the neurofilament transport. The transport of neurofilaments is uniformly impaired by IDPN along the whole axon.