“…However, a long-standing puzzle in this area is that preclinical studies have consistently found that rats treated with amphetamine or cocaine, and then withdrawn, are hypersensitive to the psychomotor activating and incentive motivational effects of these "indirect agonists" (Robinson and Berridge, 1993), and even more importantly, to the psychomotor effects of direct-acting D2 agonists (Ujike, et al, 1990, De Vries, et al, 2002, Edwards, et al, 2007. Studies examining the effects of cocaine treatment on D2 receptor binding in rodents are mixed, with reports of increases (Trulson andUlissey, 1987, Peris, et al, 1990), decreases (Kleven, et al, 1990, Maggos, et al, 1998 or no change (Dwoskin, et al, 1988, Claye, et al, 1995.…”