Open-field behavior in dopamine-depleted rat pups and their mothers

Possible changes in the behavior of rat mothers and their pups were investigated by administering intracisternal injections of 6-hydroxydopamine (6-OHDA) or its vehicle to 5-day-old rats. Administration of the neurotoxin resulted in a significant depletion of whole-brain dopamine levels to 23% of control levels, whereas norepinephrine levels were reduced to 83% of controls. Open-field behavior revealed that the 6-OHDA-treated rat pups were hypoactive, in terms of decreased square crossings, at 15 days of age, yet were hyperactive at 30 days of age. Toxin-treated pups also showed lower urination scores at 25 and 30 days of age. Mothers' open-field behavior was virtually unaffected by the treatment status of their offspring (i.e., 6-OHDA vs. vehicle-treated), although several of the mothers' behaviors decreased with repeated measures over days.