Figure 5

Measurement of the vocalization threshold using a pressure algometer test to examine the pharmacological efficacy of drugs on traumatic disk puncture-initiated discogenic pain (tested during weeks 7 through 9). Administration of pregabalin (20 mg/kg), morphine (6.7 mg/kg), celecoxib (selective inhibitor of COX-2, 50 mg/kg), ketorolac (COX-1 and COX-2 inhibitor, 20 mg/kg) or control vehicle by either oral gavage or intraperitoneal injection followed by primary pressure pain assessment by algometer. Morphine demonstrated a potent analgesic drug effect with a single administration, whereas pregabalin, celecoxib and ketorolac use led to no significant behavioral changes compared to saline control. *P < 0.001 compared to the other drug groups; †P < 0.001 compared to presurgery baseline (time 0). COX-1 = cyclooxygenase 1; COX-2 = cyclooxygenase 2.