Animal experiment:

In the experiment, 39 C57 and 40 DBA mice are tested over a three-day period. On days 1 and 2, mice are placed into the VT for 60 min and locomotor behavior is recorded. On the third day, mice are placed into the VT chamber for 60 min. Following the 60-min period, mice are removed from the chambers and administered 0, 1.0, 3.0, or 10.0 mg/kg of RO-10-5824 (n=9-11 per group). Mice are assigned to drug group pseudo-randomly, with each dose being represented in a cage of four mice. A novel paper cup measuring 9.5 cm in height and 7.5 cm in diameter at the rim is placed upside down in the center of each open field and secured to the floor with tape. Mice are returned to the VT 10 min following injection and tested for an additional 30 min.

Ro 10-5824 dihydrochloride is a selective dopamine D4 receptor partial agonist, with Ki of 5.2 nM.

RO-10-5824 shows high affinity binding with a Ki=5.2±0.9 nM (n=3), 250-fold selectivity vs human D3R, and >1000 fold selectivity for D4 vs human D2, D1, and D5 receptors. RO-10-5824 stimulates 35S-GTPγS binding with an EC50 value of 205±67 nM (n=7) and maximal induction at 36±4% above basal level[2].

Ro 10-5824 (3 mg/kg) increases the success rate in the ORD task. At doses of 1 and 3 mg/kg, Ro 10-5824 increases baseline gamma band activity in the frontal cortex. Ro 10-5824 has no effect on spontaneous locomotion[1]. RO-10-5824 (10.0 mg/kg) does not increase center entries in the open field in a single 60-min session without the novel object present, nor does it increase overall transitions in the initial experiment with C57 mice[2].

References:
[1]. Nakazawa S, et al. Behavioral and neurophysiological effects of Ro 10-5824, a dopamine D4 receptor partial agonist, in common marmosets. Psychopharmacology (Berl). 2015 Sep;232(17):3287-95.
[2]. Powell SB, et al. RO-10-5824 is a selective dopamine D4 receptor agonist that increases novel object exploration in C57 mice. Neuropharmacology. 2003 Mar;44(4):473-81.