Figure 2.

Stress response evoked by the functional inactivation of the right inner ear by trans-tympanic injection of 3% ropivacaine. (A) ACTH and corticosterone plasma concentrations (pg/ml and ng/ml respectively) measured by radioimmunoassay of trunk blood taken from rats sacrificed 30 min after the onset of the symptoms of unilateral vestibular loss. Symptom severity (spontaneous ocular nystagmus, barrel-rolling, postural asymmetry) was estimated on a behavioral scale as described in detail in Bergquist et al. (2008). Note sham-treated animals (n = 5) developed no symptoms and maintained low ACTH and corticosterone levels, while ropivacaine-treated animals (n = 6) developed marked behavioral symptoms and showed ACTH and corticosterone levels that were elevated in relation to the severity of the symptoms. (B) Mean ± SD of plasma ACTH and corticosterone concentrations in the sham-treated group (open bars) and the ropivacaine-treated group after functional unilateral labyrinthectomy (UL, closed bars). Bergquist, F., Brunton, P., and Dutia, M. B., unpublished data.