This study was designed to determine the effect of hypoxia on the kinetic parameters of D1 and D2 receptors in striatum of newborn piglets. The piglets were anesthetized and mechanically ventilated. One hour of hypoxic insult was generated by decreasing the oxygen fraction in the inspired gas(FiO2) from 22% to 7%-8%. The changes in cortical oxygen pressure (cortical pO2) during the hypoxic period and two hours of reoxygenation were measured by oxygen dependent quenching of the phosphorescence of a phosphor dissolved in the blood. At the end of each study, the brain was rapidly removed and the striatum dissected out. Striatum was then homogenized, membrane preparations were isolated, and D1 and D2 receptor binding assayed. The control kinetic parameters for D1 were Kd = 1.61 ± 0.06 nM and Bmax = 13.5± 1.2 fmoles/mg protein and for D2 were Kd = 0.47± 0.05 nM and Bmax = 417.3 ± 75.2 fmoles/mg protein. A one hour period of hypoxia resulted in no statistically significant changes in Kd or Bmax for either receptor. However, by two hours of reoxygenation following a hypoxic episode, the Kd (2.90 ± 0.17 nM) for D1 was significantly higher (p<0.05) than those values for controls and for hypoxia. Bmax did not significantly change. The results show that one hour hypoxia can produce long lasting changes in properties of D1 dopamine receptors, which can affect brain metabolism and dopamine related behavior (funded by NS-31465).