[Effects of l-stepholidine on open-field behavior and discrimination learning in mice].
Effects of l-stepholidine (l-SPD), a new DA-receptor antagonist, apomorphine (Apo, DA-receptor agonist) and haloperidol (Hal, DA-receptor antagonist) on open-field behavior (OFB) and discrimination learning in mice were studied. The ambulation and rearing caused by novel environmental stimuli were taken as the index of OFB. The discrimination learning was carried on 20 trials every day for 7 days in Y-maze. The numbers of correct responses were taken as the index of discrimination learning test. 
 1) l-SPD 2.5 or 10 mg/kg ip or Hal 0.5 mg/kg ip led to the inhibition of OFB. 2) l-SPD 10 mg/kg decreased the discrimination learning from d 3 to d 7, but l-SPD 2.5 mg/kg appeared to be less effective in this respect, Hal decreased and Apo increased discrimination learning. 
 It is suggested that the dopaminergic drugs influence OFB and discrimination learning through different dopaminergic pathway. Lower dose of l-SPD can play some role of DA antagonist without the impairment of learning.