Erratum to “Dopamine D2/D3 receptors modulate cocaine’s reinforcing and discriminative stimulus effects in rhesus monkeys”: [Drug Alcohol Depend. 54 (1999) 97–110]

3.1.2. Acquisition of quinpirole self-administration In cocaine-naive monkeys 1191 and 1192, responding was reliably maintained under an FI 3-min schedule of food presentation (Fig. 2, open squares). For monkey 1191, substitution of 0.01 mg/kg/inj quinpirole for food resulted in an immediate decline in total number of reinforcers earned during the 4-h session (Fig. 2, top panel). Across the last three sessions of quinpirole availability, the mean number of injections delivered/4h session was 8.7 (94.0) and the mean rate of responding was 0.06 (90.02) responses/min. When food was again made available, responding returned to pre-drug levels. Substitution of a lower or a higher dose of quinpirole (0.003 and 0.03 mg/kg/inj) for food resulted in nearly complete elimination of responding within 2–3 sessions. The mean number of injections/session was 1.0 (90.0) and 3.3 (92.1), respectively. When saline was substituted for food for five sessions, responding declined to near zero, with a mean of 1.7 (90.6) saline injections received over the last three sessions. When 0.03 mg/kg/inj cocaine was made available for self-administration, responding was maintained throughout the five consecutive sessions, with a mean of 41.0 (92.6) cocaine injections/session and a mean response rate of 0.89 responses/min over the last three sessions (Fig. 2, top panel). For the second cocaine-naive subject (monkey 1192), 0.01 mg/kg/inj quinpirole did not maintain responding when substituted for food, with a mean of 2.0 (90.0) injections/session over the last three sessions (Fig. 2, bottom panel). In contrast, when 0.03 mg/kg/inj quinpirole was available, responding occurred at high rates during all sessions, and the mean number of injections delivered over the last three sessions was 38.0 (96.6). The monkey exhibited excessive locomotor activity during these sessions and afterwards appeared very active and aggressive (e.g. bearing teeth). After re-establishing the food baseline, cocaine (0.03 mg/kg/inj) was made available for self-administration for five sessions. The mean number of injections delivered over the last three sessions was 64.0 (95.6) and the mean rate of responding was 3.38 (90.77) responses/min. When saline was made available for six consecutive sessions, the mean number of injections over the last three sessions was 17.7 (93.2) and the mean saline-maintained response rate was 0.16 (90.05) responses/min (Fig. 2, bottom panel). In monkey 1192, in order to assess whether the high rates of responding maintained by 0.03 mg/kg/inj quinpirole were due to response-contingent drug presentation or to increases in locomotor activity, the effects of 0.03 mg/kg/inj quinpirole were evaluated under an FT schedule of non-contingent drug presentation. When 0.03 mg/kg/inj quinpirole was available for self-administration under the FI 3-min schedule, the mean interinjection interval was 6 min. Therefore, the same PII of original article S0376 -8716 (98 )00162 -8. * Corresponding author. Fax: +1-336-7168501. E-mail address: mnader@wfubmc.edu (M.A. Nader)