  We present CO(1-0) observations of the high-redshift quasi-stellar objects
(QSOs) BR 1202-0725 (z=4.69), PSS J2322+1944 (z=4.12), and APM 08279+5255
(z=3.91) using the NRAO Green Bank Telescope (GBT) and the MPIfR Effelsberg
100m telescope. We detect, for the first time, the CO ground-level transition
in BR 1202-0725. For PSS J2322+1944 and APM 08279+5255, our observations result
in line fluxes that are consistent with previous NRAO Very Large Array (VLA)
observations, but they reveal the full line profiles. We report a typical
lensing-corrected velocity-integrated intrinsic CO(1-0) line luminosity of
L'(CO) = 5 x 10^10 K km/s pc^2 and a typical total H_2 mass of M(H2) = 4 x
10^10 M_sun for the sources in our sample. The CO/FIR luminosity ratios of
these high-z sources follow the same trend as seen for low-z galaxies, leading
to a combined solution of log(L_FIR) = (1.39 +/- 0.05) x log(L(CO))-1.76. It
has previously been suggested that the molecular gas reservoirs in some quasar
host galaxies may exhibit luminous, extended CO(1-0) components that are not
observed in the higher-J CO transitions. Utilizing the line profiles and the
total intensities of our observations and large velocity gradient (LVG) models
based on previous results for higher-J CO transitions, we derive that emission
from all CO transitions is described well by a single gas component where all
molecular gas is concentrated in a compact nuclear region. Thus, our
observations and models show no indication of a luminous extended, low surface
brightness molecular gas component in any of the high-redshift QSOs in our
sample. If such extended components exist, their contribution to the overall
luminosity is limited to at most 30%.
