Striatonigral Tachykinin Biosynthesis

Substance P (SP) and substance K (SK), two structurally related neuropeptides belonging to the tachykinin family, are derived from a single preprotachykinin (PPT) gene [1,2]. Recent evidence has suggested that these peptides are probably co-localized within the striatonigral tract [3]. Interactions of SP and dopamine (DA) in the basal ganglia are well known although the exact mechanisms are unclear [4]. DA antagonists decrease striatonigral tachykinins and striatal PPT mRNA levels [5–7; Bannon et al., this volume]. However, there are conflicting reports on effects of DA agonists on striatonigral substance P concentrations [7,8]. No data has been published on the effects of DA agonists on the levels of striatonigral SK or PPT mRNA. The present study attempts to clarify the effect of DA agonists on striatonigral SP and SK biosynthesis.