Intranigral injection of selective neurokinin-1 and neurokinin-3 but not neurokinin-2 receptor agonists biphasically modulate striatal dopamine metabolism but not striatal preprotachykinin-A mRNA in the rat.

Tachykinins are highly concentrated in striatum and substantia nigra. Intranigral injection of selective neurokinin-1 and neurokinin-3 but not neurokinin-2 receptor agonists significantly decreased striatal dopamine metabolism at early time points (1 and 5 min) but increased dopamine metabolism at late time points (60 and 180 min). This probably modified striatal dopamine release, was, however, not able to influence striatal preprotachykinin-A gene expression. The data suggest that tachykinins modulate nigro-striatal dopamine neurons via neurokinin-1 and neurokinin-3 receptors and the modified dopamine stimulus is not strong enough to influence striatal tachykinin neurons.