Figure 4: Effect of 6-aryl-9-substituted-6,9-diazaspiro-[4,5]decane-8,10-diones series 1– 9 in the hot-plate test in adult male albino mice. The animals were classifi ed into XI groups of mice. Group I served as the control group and received saline. Group II received tramadol hydrochloride at dose 0.095 mmol/kg body weight (25 mg/kg) and groups III 8211; XI each received one of the test compounds by intraperitoneal injection at dose 25 mg/kg (0.066– 0.079 mmol/kg) for each compound. The animals were observed for their response toward pain stimulus after administration of the test compound at defi nite time intervals. Each value represents the mean reaction time (s) ± SEM. *Significant difference from control at P < 0.05; #significant difference from tramadol hydrochloride at P < 0. 05.