Table 1

AD50 values for SR blockade of cannabinoid-induced antinociceptive effects after administration to mice

SR AD50Values (± CLs)
i.p. (mg/kg)i.c.v. (μg/mouse)i.t. (μg/mouse)
i.c.v. (μg/mouse)
  Δ9-THC (50)1.4  (1.1–2.3)4.2  (3.4–5.4)NT
  Δ8-THC (150)0.47  (0.2–1.6)8.1  (5.9–9.9)**NT
  CP55,940 (5)0.88  (0.52–1.3)2.8  (1.2–6.6)NT
  Deoxy-HU210 (20)blocked1-a blocked1-a NT
i.t. (μ/mouse)
  Δ9-THC (50)0.76  (0.61–1.8)NT28.6  (20.2–40.5)1-a
  Δ8-THC (150)0.9  (0.5–2.2)NT50.2  (40.4–63)1-a
  CP55,940 (5)0.1  (0.08–0.26)***NT20.9  (19–50.2)1-a
  Anandamide (100)15.4  (13.8–28.6)1-150 NTblocked1-b
  Deoxy-HU210 (20)0.4  (0.3–0.8)NTblocked1-b

Mice were injected with SR (i.p., i.c.v. or i.t.) or vehicle (DMSO for i.t. administration; 1:1:18, emulphor/ethanol/saline, for i.c.v. and i.p. administration). One hour later the mice were administered approximate ED80 doses of various cannabinoids i.t. and/or i.c.v. The mice were tested 15 min later using the tail-flick test. At least 12 mice were used per treatment group. The % inhibition of antinociception in the presence of SR was determined as described in “Materials and Methods.”

  • 1-150  significantly different from Δ9-THC, Δ8-THC and CP55,940 (all i.t.); ** significantly different from Δ9-THC and CP55,940 (all i.c.v.); *** significantly different from Δ9-THC and Δ8-THC (both i.t.).

  • 1-a indicates that block by SR was incomplete (<70%) up to 100 μg/mouse i.t.

  • 1-b The AD50 could not be determined where maximal blockade was less than 50%.

  • NT indicates that the combination was not tested.