Table 2.

ED₅₀ values and 95% confidence limits for drugs to decrease rate of operant responding (Response Rate) and rectal temperature (Temperature) before, during, and after discontinuation of daily Δ⁹-THC (32 mg/kg) treatment

	ED50 in mg/kg (95% confidence limits)	Potency ratioa (95% confidence limits)
Δ9-THC response rate
Before	5.64 (3.52–9.03)
During	46b (3.7–570)	8.2 (1.4–48)
After	17.9b (7.23–44.5)	3.2 (1.4–7.5)
Δ9-THC temperature
Before	10.2 (7.06–14.8)
During	c
After	23.0b (15.8–33.5)	2.3 (1.4–3.7)
CP 55940 response rate
Before	0.12 (0.069–0.21)
During	0.20 (0.11–0.35)	1.7 (0.8–3.5)
After	0.17 (0.049–0.60)	1.4 (0.5–4.1)
CP 55940 temperature
Before	0.48 (0.37–0.67)
During	c
After	2.01b (1.26–3.18)	4.2 (2.5–7.2)
Anandamide response rate
Before	5.45 (3.42–8.69)
During	7.46 (3.23–17.2)	1.4 (0.6–2.9)
After	5.25 (3.32–8.31)	1.0 (0.5–1.8)
Anandamide temperature
Before	19.2 (15.3–24.2)
During	20.4 (14.7–28.4)	1.1 (0.7–1.6)
After	16.1 (12.4–20.7)	0.8 (0.6–1.2)
Midazolam response rate
Before	4.03 (2.54–6.41)
During	23.3 (13.1–41.3)	d
After	4.37 (2.32–8.23)	1.1 (0.5–2.2)
Midazolam temperature
Before	11.0 (6.65–18.3)
During	22.4 (8.25–60.7)	2.0 (0.8–5.4)
After	9.77 (5.65–16.9)	0.9 (0.4–1.8)

^aPotency ratios and 95% confidence limits are ED₅₀ values determined during or after discontinuation of Δ⁹-THC treatment divided by the ED₅₀ value determined before Δ⁹-THC treatment

^bSignificantly different from Before

^cED₅₀ value not determined; the largest dose did not produce greater than 50% effect

^dPotency ratio not calculated because slopes were significantly different