Role of dopamine D1 receptors in novelty seeking in adult female Long-Evans rats

Adult Long-Evans ovariectomized female rats received injections of the DA D1 antagonist SCH 23390 (0, 0.03 and 0.3 mg/kg, i.p.) and were observed in an open field apparatus (OFA) with a novel object. Results indicate that a significant effect of SCH 23390 was found on several measures of novelty seeking and activity, with the high dose producing a significant decrease in (1) approaches to and (2) rears while approaching the novel object, (3) latency to interact with the novel object, (4) in time interacting with the novel object, (5) anxious behavior (as measured by rears) and (6) locomotor activity (LMA), as compared to both the saline and low dose. Interestingly, the effects of SCH 23390 on approaches and rears were not significant when LMA was factored into the analysis (repeated measures ANCOVA), however, marked results were still found on time interacting with the novel object. These data demonstrate that SCH 23390 produced dose-dependent effects on novelty seeking that were independent of LMA, implicating D1 receptors in the incentive-motivational aspect of novelty seeking in adult gonadectomized female rats.