EFFECTS OF ACUTE TREATMENT WITH DOPAMINERGIC DRUGS ON OPEN-FIELD BEHAVIOR OF ADULT MONKEYS TREATED WITH LEAD DURING THE FIRST YEAR POSTPARTUM

A pharmacological challenge of nonhuman primate open field behavior, s imilar to that which pre previously assessed the cholinergic system (1 0), was used here to measure potential lead-induced alterations in the dopaminergic system. Monkeys that had been treated with lead during t he first year postpartum were assessed at 7 years of age in the open f ield after acute intramuscular injection of apomorphine (0.0-0.3 mg/kg ) or haloperidol (0.0-30 mu g/kg). Duration of environmental explorati on indicated a possible greater responsivity to 0.2 mg/kg apomorphine in the lead-treated monkeys; however, in all other behaviors, lead-tre ated monkeys responded to both drugs similarly to controls. Regardless of lead treatment, apomorphine administration decreased duration of i nactivity and increased environmental exploration; the latter possibly included an increase in stereotypical behavior that might have been r ecorded as environmental exploration. Haloperidol had no significant e ffects on open field behavior over the dose range tested. Open field b ehavioral alterations previously reported for these monkeys at 4-6 yea rs of age were no longer strongly exhibited by the lead-treated monkey s in any portion of the current study. Latency to enter the open field was marginally increased in the lead-treated group but levels of envi ronmental exploration were comparable to controls. These results indic ate an attenuation of lead-related effects with maturity and/or famili arity with the open field.