The blood‐brain permeabilities of L‐[3H]tyrosine and the tyrosine hydroxylase (TH) inhibitor β‐[14C]methyl‐para‐tyrosine ([14C]AMPT) were determined in rat striatum, a brain region rich in TH activity, and in other brain regions containing relatively little TH activity. In striatum, the unidirectional clearance rate (K1) for L‐[3H]tyrosine (6.2 ml hg‐ −1 min−1) was significantly greater than the rates for L‐[14C]AMPT (2.8 ml hg−1 min−1) and D‐[14C]AMPT (0.8 ml hg−1 min−1). The apparent volume of distribution (Vf) for L‐[14C]AMPT in striatum (72.5 ± 4.0 ml hg‐1) did not differ from the Vf in other brain regions. The homogeneous distribution of L‐[14C]AMPT in rat brain indicates that labeled AMPT is unsuitable for the study of TH in vivo by quantitative autoradiography. © 1994 Wiley‐Liss, Inc.
- Positron emission tomography
- Tyrosine hydroxylase
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience