Effects of acute 4-chlorokynurenine (4-Cl-KYN) administration, with and without D-cycloserine (DCS), on task omissions in the delay non-match to position (DNMTP) task. Data represent the number of omissions (mean ± SEM), in a single group of rats (n = 7), during four drug sessions (order randomized: vehicle, 25 mg/kg 4-Cl-KYN, 100 mg/kg 4-Cl-KYN, 100 mg/kg 4-Cl-KYN+ 30 mg/kg DCS). Acute administration of 4-Cl-KYN did not significantly increase the number of omissions at either the high dose (100 mg/kg) or the low dose (25 mg/kg). Co-administration of 4-Cl-KYN and DCS also had no significant effect on the number of omissions despite the fact that DCS returned choice accuracy to control levels (cf. Fig. 4)