Mycobacterium tuberculosis

Morphine was purchased from Millipore Sigma (St. Louis, MO). THC was obtained from the National Institute on Drug Abuse (Bethesda, MD). Drugs were administered by s.c. (morphine) or i.p. (THC) injection in volumes of 1 ml/kg. Morphine was dissolved in saline, which served as the vehicle for morphine. When morphine was given alone, doses were 0.032, 0.1, 0.32, 1.0, or 3.2 mg/kg. THC was dissolved in a 1:1:18 ethanol:cremophor:saline solution, which served as the vehicle for THC. When THC was given alone, doses were 0.5, 1.0, 2.0, or 4.0 mg/kg. Morphine:THC dose equivalency ratios at 1:1, 3:1, and 1:3 were calculated based on von Frey data (see Data Analysis section below for additional details), and several dilutions (5, 10, 20, 40, or 80%) of each equivalency ratio were administered (Table 1). Experimenters were blind to dose. CFA (1 mg/ml heat-killed Mycobacterium tuberculosis) was purchased from Millipore Sigma (St. Louis, MO). Isoflurane was purchased from Patterson Veterinary Supply (Everett, WA).

Drugs were obtained from the National Institute on Drug Abuse (Bethesda, MD; THC and CBD) and Cayman Chemical Co. (Ann Arbor, MI; CBD). THC (0.05–2.0 mg/kg) and CBD (0.05–6.0 mg/kg) were dissolved in a 1:1:18 ethanol:cremophor:saline solution, which also served as the vehicle. CBD:THC combinations included CBD (0.05, 0.1, 1.0, & 2.0 mg/kg) in combination with THC 0 mg/kg (vehicle), THC (0.05, 0.1, 0.5, 1.0, & 2.0 mg/kg) in combination with CBD 0 mg/kg (vehicle), combinations with equal mg/kg CBD and THC doses (1:1 dose ratio), low CBD + high THC combinations (1:3 dose ratio), and high CBD + low THC combinations (3:1 dose ratio). Actual doses administered in each combination are shown in Table 1. Because studies using neuropathic pain models demonstrated that 1:1 CBD:THC interactions were only synergistic at very low doses^{9 (link), 42 (link)}, we tested 1:1 combinations down to 0.05 and 0.1 mg/kg -- doses below those that typically produce antinociceptive effects when given alone in rodent chronic pain models.^{6 (link), 9 (link), 42 (link)} Drugs were administered by i.p. injection in volumes of 1 ml/kg. Experimenters were blind to dose. CFA (1 mg/ml heat-killed Mycobacterium tuberculosis) was purchased from Millipore Sigma (St. Louis, MO). Isoflurane was purchased from Patterson Veterinary Supply (Everett, WA).