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placed in scintillation vials to which 1 mL of methanol and 2
mL of 0.2 M HCl were added to extract the accumulated [3H]-
dopamine. Radioactivity was determined by liquid scintillation
spectrometry at an efficiency of approximately 30%. The
reported values represent specific uptake from which nonspe-
cific binding to filters was subtracted.
3. An a lysis of Da ta . Saturation and displacement data
were analyzed by the use of the nonlinear least-squares curve-
fitting computer program LIGAND.36 Data from replicate
experiments were modeled together to produce a set of
parameter estimates and the associated standard errors of
these estimates. In each case, the model reported fit signifi-
cantly better than all others according to the F test at p <
0.05. The Ki values reported are the dissociation constants
derived for the unlabeled ligands. Uptake data were analyzed
using standard analysis of variance and linear regression
techniques.37 IC50 values were calculated using the linear
portion of the concentration-response curve (linear regression
p < 0.05).
Ack n ow led gm en t . R.H.K. was supported by a
NIDA-sponsored National Research Council Fellowship.
M.J .R. was funded by a National Institutes of Health
Intramural Research Training Award Fellowship. We
thank Richard Loeloff and Phyllis Terry for expert
technical assistance. We also thank Dr. Brian Hoffman
for valued insight and editorial assistance on the final
version of this manuscript. Animals used in this study
were maintained in facilities fully accredited by the
American Association for the Accreditation of Labora-
tory Animal Care (AAALAC), and all experimentation
was conducted according to the guidelines of the Insti-
tutional Care and Use Committee of the Intramural
Research Program, National Institute on Drug Abuse,
NIH, and the Guide for Care and Use of Laboratory
Animals of the Institute of Laboratory Animal Resources,
National Research Council, Department of Health,
Education and Welfare, Publication (NIH) 85-23, revised
1985.
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