The actions of xylamine on central noradrenergic neurons

The effects of xylamine (N-2-chloroethyl-N-ethyl-2-methylbenzylamine) on catecholamine content and uptake in rat brain were examined after systemic administration. Four hours after doses of 10 to 50 mg/kg i.p. of xylamine, norepinephrine uptake in synaptosomal preparations from cortex was reduced, but dopamine uptake in striatal preparations was unaffected. The levels of norepinephrine in the cortex and hypothalamus were depressed over this dose range, whereas dopamine levels in the striatum again were unaltered. The depletion of norepinephrine from the cortex and hypothalamus was also seen histologically by fluorescence histochemistry. When brain tissue was examined 10 days after a single 25 mg/kg dose, the depletion persisted in cortex and hypothalamus, and although there was a decrease in fluorescence intensity there was no clear evidence of a decreased number of catecholamine-containing processes that would have indicated neurotoxic effects. There was also no gliosis (an indicator of neuronal degeneration) in any of the brain areas or damage to the blood brain barrier. Thus, in contrast to 6-hydroxydopamine, xylamine appears to have selective action on norepinephrine systems and does not appear to be a nonselective neurotoxin.