Effect of dizocilpine maleate on discriminative properties of methamphetamine in rats.
AIM
To study the effect of (+)-10, 11-dihydro-5-methyl-5H-dibenzo [a, d] cyclohepten-5, 10-imine maleate(dizocilpine maleate, MK-801) on the discriminative behavior of methamphetamine (MA).


METHODS
Two lever and a fixed-ratio schedule of food presentation reinforcement program were used in discrimination test session.


RESULTS
Rats can shape and maintain the discriminative behavior for MA (1 mg/kg, s.c.) and saline (1 mL/kg, s.c.). On pretreatment with dizocilpine maleate (0.1 mg/kg) in MA dependent rats, the correct discrimination percentage of MA was markedly decreased; but pretreatment with dizocilpine maleate (0.025, 0.05 mg/kg) did not block discrimination behavior of MA in antagonistic test. After injection of dizocilpine maleate (0.1 mg/kg) alone in MA dependent rats, six of the seven rats partially or completely responded on the MA associated lever whereas one did not. All of the rats had no substitution after injection of dizocilpine maleate (0.025, 0.05 mg/kg).


CONCLUSION
N-methyl-D-aspartate (NMDA) receptor may be involved in psychological dependence of MA.