DSP-4: a novel compound with neurotoxic effects on noradrenergic neurons of adult and developing rats.

The pharmacological actions of the compound N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine hydrochloride (DSP-4) are compatible with a specific neurotoxic effect on both peripheral and central noradrenergic neurons. The systemic injection of DSP-4 to adult rats transiently alters sympathetic neurons in the periphery but in the central nervous system the compound determines a marked and prolonged reduction of noradrenaline (NA) levels in all brain regions studied. When DSP-4 was injected systemically to rats at birth in doses ranging from 6.25 to 100 micrograms/g, no changes were found in peripheral sympathetic neurons 40 days later. On the contrary, in the same conditions and in relation to the dose injected, there were marked and persistent changes in the levels of NA in different regions of the brain. In the cerebral cortex and the spinal cord, the neonatal injection of SDP-4 produced a marked and long-lasting depletion of NA levels, similar to that observed after injection of the compound to adult rats. These changes were accompanied by a moderate increase in brain stem NA and a marked elevation of the amine in the cerebellum. These changes, different from the depletion observed in both regions when the compound was given to adult rats, are however similar to those observed after the neonatal injection of the neurotoxic compounds 6-hydroxydopamine or its precursor amino acid, 6-hydroxydopa. This indicates that probably central noradrenergic neurons respond in the same manner after different chemical injuries. DSP-4 crosses the placental barrier because when it was given to pregnant rats at the end of gestation, long-term changes were found in brain NA levels in their offspring, similar to those produced by the neonatal administration of the compound. This new neurotoxic compound provides a very useful tool for the study of noradrenergic neurons both in adult animals and during ontogenesis.