Mechanical withdrawal thresholds of postnatal day (P)3 rat pups prior to (baseline) and at intervals (15, 30, 45, 60 min, and 24 h) following intrathecal injection of saline or 0.5 μl/g of 0.5% levobupivacaine. Graphs represent the log₁₀ stimulus–response relationship between number of hind limb withdrawal responses (0–5) and mechanical stimulus (grams, g) applied with graded von Frey hairs. At 15 min, thresholds were higher in the levobupivacaine (log EC₅₀ 11.3 g; 95% CI, 9.2–13.5) than saline (log EC₅₀ 2.0; 95% CI, 1.7–2.3) group. Data points = pooled mean ± SEM for saline (n = 11) and levobupivacaine (n = 9) groups.