The Effect of Local Anaesthetics on Apoptotic Neurodegeneration in the Developing Brain in Mice

Abstract

Introduction: General anaesthetics induce the neuronal apoptosis in the immature brain. Regional anaesthesia using local anaesthetics (LA) can decrease the dose of general anaesthetics or even be an alternative to general anaesthesia. However, no report has examined the effect of LA on brain apoptosis. Therefore, this study investigated the effect of LA on neuronal apoptosis.

Methods: Fifty-one 7-day-old C57BL6 mice were allocated into control (group C), lidocaine (group L), lidocaine plus midazolam (group LM), and isoflurane (group I) groups. Group C received normal saline administration. Groups L and LM were injected with lidocaine (4 mg/kg, subcutaneously) and with midazolam (9 mg/kg, subcutaneously). Group I was exposed to 0.75 vol% isoflurane for 6 h. After 6 h, apoptotic neurodegeneration was assessed using caspase-3 immunostaining and TUNEL staining.

Results: For the entire brain, neuronal cells exhibiting caspase-3 activation were observed more frequently in group LM and group I than group C (P = 0.039 and 0.002). In the thalamus, apoptosis of group L was significantly more than that of group C (P = 0.001), but less than group I (P = 0.002). In the cortex, the mice of group I experienced more apoptosis than the mice of group L and C (all P < 0.001). In the caudate nucleus, apoptosis of group LM was more observed than that of group L (P = 0.006) and C (P = 0.002). On TUNEL staining, the number of cells per mm2 undergoing DNA fragmentation in group C was less than in groups LM and I (P = 0.006 and P = 0.002, respectively). Apoptosis of group I was also more observed than that of group L (P = 0.036). More apoptosis occurred in group L than in group C, but the difference was not significant (P = 0.05).

Conclusions: LA may induce neuronal apoptosis in the immature brain, although not to the same degree as inhalational anaesthetics. Adding midazolam to lidocaine has an effect on neuronal apoptosis similar to that of inhalational anaesthetics. More research regarding the degree and exact mechanism of brain apoptosis caused by LA is needed.