Figure 2. Psilocybin does not improve mechanical or thermal hypersensitivity in male or female mice in three pain models.

(A) Legend and timeline for pain models and assessments. Relative to baseline testing: SNI surgery was performed 7 days prior; AIMP involves two acidic normal saline injections, 6 days and 1 day prior; CFA injection to the paw occurs 1 day prior. Psilocybin injections were administered after baseline testing. Hargreaves test (thermal) is quantified by paw withdrawal latency. Von Frey test (mechanical) is quantified by paw withdrawal threshold (PWT). Muscle sensitivity to tweezer force is quantified by muscle withdrawal threshold (MWT).

(B,C) SNI produces neuropathic pain and long-lasting thermal and mechanical hyperalgesia. 7 days after surgery, in the acute phase, mice (males and females n=6 per group) were injected with either psilocybin or vehicle control and tested out to 24 hours. Two weeks later, in the chronic pain phase, mice received a second injection and again were tested out to 24 hours. Psilocybin has no effect on either thermal or mechanical hyperalgesia at the doses tested. Two-way repeated measures ANOVA (Thermal: F (32, 440) = 4.861 P<0.0001; Mechanical: F (32, 440) = 7.979 P<0.0001). Post-hoc Tukey Test, * P < 0.0001 versus control.

(D,E) AIMP produces long-lasting cutaneous thermal and muscle mechanical hyperalgesia. 24 h after initiation of pain, in the acute phase, mice (males and females n=5–7 per group) were injected with either psilocybin or vehicle control and tested out to 24 hours. Two weeks later, in the chronic pain phase, mice received a second injection and again were tested out to 24 hours. Psilocybin has no effect on either cutaneous thermal or muscle mechanical hyperalgesia at the doses tested. Two-way repeated measures ANOVA (Thermal: F (32, 440) = 2.809 P<0.0001; Mechanical: F (32, 440) = 11.99, P<0.0001) Post-hoc Tukey Test, * P < 0.0001 versus control.

(F,G) CFA produces long-lasting thermal and mechanical hyperalgesia due to inflammation of the paw. 24 h after CFA injection, in the acute pain phase, mice (males and females n = 5–7 per group) were injected with either psilocybin or vehicle control and tested out to 24 hours. Two weeks later, in the chronic pain phase, the mice received a second injection and were again tested out to 24 hours. Psilocybin has no effect on either thermal or mechanical hyperalgesia at the doses tested. Two-way repeated measures ANOVA (Thermal: F (32, 280) = 3.664 P<0.0001; Mechanical: (32, 280) = 5.242). Post-hoc Tukey Test, * P < 0.0001 versus control.