IL1R1 and microtia: To accomplish this we investigated whether: (i) sciatic nerve injury increases the expression of IL-1β in the lumbar spinal cord dorsal horn; (ii) IL-1R1, a functional receptor of IL-1β, is expressed in spinal astrocytes; (iii) the blockade of IL-1R1 using the recombinant IL-1 receptor antagonist (IL-1ra) modulates astrocyte P450c17 expression and pathological astrocyte activation; and (iv) this modulation is associated with the development of MA induced by peripheral nerve injury.