[SDZ HDC 912 as a dopamine receptor partial agonist: the effect on spontaneous locomotor activity in mice]

To clarify if N-((8-alpha)-2-chloro-6-methylergoline-8-yl)-2,2- dimethylpropanamide (SDZ HDC 912) acts as a dopamine receptor partial agonist in vivo, we investigated the effect of SDZ HDC 912 on spontaneous locomotor activity in mice. Oral administration of SDZ HDC 912 (1-1,000 micrograms/kg) caused no change in the locomotor activity. After the treatment with alpha-methyl-p-tyrosine (200 and 100 mg/kg, ip, 3 and 1 h prior to the experiment, respectively) in combination with reserpine (5 and 1 mg/kg, ip, 24 and 2 h prior to the experiment, respectively), oral SDZ HDC 912 at the dose of 10 but not of 1,000 micrograms/kg produced an increase in the locomotor activity 30 min after the administration. These results suggest that SDZ HDC 912 may exhibit dopamine receptor agonistic effect under certain conditions, such as supersensitivity and/or catecholamine depletion.