2 μL of a solution of hypoxanthine (20 pmol/2 μL) or vehicle (saline 0.9 %) was administered in the right striatum of the rats 1 μL per minute.

The in vitro drug sensitivity of the Cambodian isolates was assessed by use of a classical isotopic 48- h test. fresh blood samples were washed three times with RPMI 1640 medium (GibcoTM, Invitrogen Corporation, France) by centrifugation (800×g, 10 min). The parasites were then tested directly without culture adaptation. The infected erythrocytes (1.5% hematocrit, 0.1–1% parasitemia) were suspended in complete RPMI medium supplemented with 10% of decomplemented human AB+ serum (Biomedia, France) and buffered with 25 mM/l Hepes and 25 mM/l NaHCO3. The mixture was distributed (200 mkl per well) into the 96-well test plates that had been pre-coated with antimalarial agents. Each plate included two drug-free control wells and one control well without parasites. The culture plates were incubated for 48 h at 37 ◦Cina5%CO2 atmosphere. [3H]Hypoxanthine (0.5 mkCi/well; Amersham Biosciences, France) was used to assess parasite growth. Each isolate was tested once in duplicate in the microplates with serial dilutions of drugs. Drug response was quantified by monitoring [3H]hypoxanthine uptake in aWallac MicroBeta Trilux counter (Perkin-Elmer, France). At the end of the incubation period, the plates were frozen at −20 ◦C and thawed to lyse the cells. After collection on glassfiber filter paper using a cell harvester, the amount of [3H]hypoxanthine incorporated into the parasites nucleoprotein was determined.