Table 2

Mean ED₅₀ values in milligrams per kilogram (±95% confidence limits) and dose ratios for SNC162, morphine, or U-50,488 after acute pretreatment with saline or 10.0 mg/kg SNC80

	ED₅₀	Dose Ratio
24-h Pretreatment to SNC162
Saline	0.62 (0.20–1.30)
SNC80	>17.37^2-a (5.38–36.05)^2-150	>28
24-h Pretreatment to morphine
Saline	0.91 (0.40–1.65)
SNC80	1.23 (0.53–2.21)	1.4
24-h Pretreatment to U-50,488
Saline	0.07 (0.05–0.09)
SNC80	0.09 (0.02–0.21)	1.3

↵2-150 95% confidence limits after SNC80 treatment do not overlap with 95% confidence limits after saline treatment.
↵2-a The highest dose tested (32.0 mg/kg SNC162) did not decrease rates of responding to ≤50% in one monkey. For analysis, an ED₅₀ value of 32.0 mg/kg was assigned for this monkey.