Local Anesthetic Treatment Significantly Attenuates Acute Pain Responding but Does Not Prevent the Neonatal Injury-Induced Reduction in Adult Spinal Behavioral Plasticity

Recent findings indicate that neonatal injury results in decreased spinal plasticity in adult subjects ( E. E. Young, K. M. Baumbauer, A. E. Elliot, & R. L. Joynes, 2007 ). Previous research has shown that acute manipulations of pain processing (i.e., administration of formalin, carrageenan, capsaicin) result in a loss of spinal behavioral plasticity ( A. R. Ferguson, E. D. Crown, & J. W. Grau, 2006 ). Moreover, neonatal injury results in a lasting reduction in adult spinally mediated plasticity resembling the deficit seen following acute manipulations in adults ( E. E. Young et al., 2007 ). The present study was designed to determine whether the effects of neonatal injury could be prevented by lidocaine administration during the initial healing period. Subjects (injured or uninjured) received lidocaine or saline on 1 of 4 administration schedules (preinjury only, postinjury only, for 24 hr postsurgery, or for 72 hr postsurgery). Results demonstrated that lidocaine administration did not prevent the hypersensitivity and reduced spinal plasticity associated with neonatal injury. This suggests that (a) the mechanisms underlying neonatal injury are independent of peripheral input in the initial healing period and (b) lidocaine is ineffective at preventing long-term spinal plasticity changes following neonatal injury.