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 MESSENGER-RNA 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 (I 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-I and neurokinin-3 receptors and the modified dopamine stimulus is not strong enough to influence striatal tachykinin neurons.