Antinociceptive Effect of Botulinum Toxin A in Persistent Muscle Pain Rat Model

OBJECTIVE: To investigate the effects of botulinum toxin on the mechanical hyperalgesia, electrophysiology and motor functions in the persistent muscle pain rat model. METHOD: A secondary mechanical hyperalgesia in the bilateral hindpaws of Sprague-Dawley rats was produced by the repeated injections of acidic saline into gastrocnemius. Botulinum toxin A (BTX-A(4): 4 U/kg, BTX-A(7): 7 U/kg) was administrated into same muscle 24 hours after a second injection of saline. The mechanical hyperalgesia was measured with withdrawal threshold to von Frey filament. The grade of muscle paralysis was evaluated with electrophysiology and the locomotor performance using inclined plane board. RESULTS: The mechanical hyperalgesia was significantly decreased from 5 days to 2 weeks in BTX-A(7) group in the injected side. The dose-dependent decreased amplitude of compound muscle action potential and reduced prevalence of endplate noise from the first day of botulinum toxin injection lasted for 4 weeks in both gastrocnemius. The maximum angle maintained at initial position on the inclined plane board did not change. CONCLUSION: Local muscular injection of botulinum toxin A reduced ipsilateral hyperalgesia dose-dependently in persistent muscle pain rat model without motor deficit. The antinociceptive mechanism of botulinum toxin might act at a local or peripheral rather than a systemic or central effect due to ineffectiveness of contralateral hyperalgesia. Clinically, botulinum toxin A might be useful for the treatment of local and referred pain of muscle origins.

Posterior Capsule Opacification and Intraocular Lens Design with In-the-bag fixated Posterior Chamber Lens

This study was performed to evaluate the correlationship between posterior capsular opacification and optic configuration of intraocular lens in extracapsular lens extraction with In-the-bag implantation of posterior chamber lens. We retrospectively studied the 455 cases of cataract operations that were performed between January 1993 and January 1995. All were in-the-bag placement and their optic designs were divided into two groups: a group of biconvex lens and a group of convex-plano lens with continuous laser ridge. The incidence of PCO in bicovex lens group was 7.0% and that of convex plano lens with laser ridge group was 7.1%. The difference in the rate of posterior capsular opacification between two groups was not statistically significant. The incidence of Nd: YAG laser posterior capsulotomy revealed 0.0% in continuous ridged group and 2.6% in biconvex group(p>0.05).