Figure 5.

Elevation of D2^High receptors by amphetamine, and reversal by haloperidol. The control level of D2^High receptors was 19.5 ± 0.6% (N = 20 rats). Haloperidol alone (0.25 mg/kg/day i.p. for 9 days) raised D2^High to 28.6 ± 2% (N = 6 rats), while amphetamine alone (1.6 mg/kg/day i.p. for 9 days followed by a drug holiday for 10 days) resulted in a D2^High level of 44.2 ± 1.3% (N = 6 rats). Haloperidol (0.25 mg/kg/day for 9 days), given after amphetamine, brought D2^High down to 34.8 ± 1.6%, a reversal of 60%, where a full reversal would have corresponded to the level brought about by haloperidol alone. (Reproduced from [70] with permission of Elsevier Inc. and Copyright Clearance Center.)