Noradrenergic action of amphetamine following degeneration of descending monoaminergic fibers in the spinal cord.

Amphetamine and methoxamine facilitated the flexor reflex in chronic spinal rats whose descending monoaminergic nerve endings were degenerated. Methoxamine, but not amphetamine, facilitated the flexor reflex in the chronic spinal rat 16-20 h after IV 6-hydroxydopamine treatment. These data indicate that amphetamine's spinal cord facilitative effects are mediated through two noradrenergic mechanisms. In the acute spinal rat, its facilitative effects in these experiments seem to be independent of the sympathetic nervous system and are probably dependent on the presence of the terminal axons of the long-descending noradrenergic pathways. In the chronic spinal rat, amphetamine's facilitative actions require the integrity of the sympathetic nervous system.