The effects of adjuvant agents added to bupivacaine on block duration times, and gene expression of calcium and sodium channels in sciatic nerve block of rat

In this experimental study, comparing of effects of one of the commonly used local anesthetic, Bupivacaine, and its combination with adjuvant agents such Epinephrine, Dexmedetomidine, and Clonidine on onset time and duration of block, were aimed. Investigation of changes of gene expression in Na+ and Ca++ channels on cell membrane of sciatic nerve also aimed. The study was performed in Research Laboratory of Experimental Animal in Department of Physiology of The University of Gaziantep after approval of The Ethics Committee of Experimental Animals. A total of 24 adult, healthy male Wistar-Albino rats weighs 200-250 g were used. The rats were divided into 4 groups each consisting of 6 with randomly. Groups were organized as: Group B: Bupivacaine (5mg/ml), Group BD: Bupivacaine + Dexmedetomidine (5µg/ml), Group BC: Bupivacaine + Clonidine (7.5µg/ml), Group BE: Bupivacaine + Epinephrine (5µg/ml). Skin of the right leg was incised 1-2 mm. at bifurcation of sciatic nerve under ketamine anesthesia. For each group, the previously prepared solution was injected under epineurium 0.2mL and skin was sutured. Sensory and motor block onset and end times were recorded following the waking up of rats. Motor block was evaluated according to the ability to walk, proprioceptive block was evaluated according to response of tactile replacement, and nociceptive block was evaluated according to response of withdrawal reflex. The sciatic nerve samples were taken for genetic evaluation after the procedure. RNA isolation, cDNA synthesis, and reverse-transcriptase polymerase chain reaction (RT-PCR) was performed for gene expression analysis of Na+ channels (SCN9A) and Ca+2 channel (TRPM2, TRPM4, TRPM7) with those examples. In the study, it was found that, BC group has the shortest onset time, and BD group has the longest duration of sensory and motor block. We considered that, adding clonidine is appropriate for rapid onset time, and adding dexmedetomidine is appropriate for longer duration for peripheral blocks. Increasing the rate of TRPM-2 which is a preliminary indicator of cell apoptosis and oxidative stress, and decreasing the rate of TRPM-7 which protects the cell from oxidative stress and anoxic cell death were observed in all groups except BE group. By the way the changes of SCN9A and TRPM2-4-7 expression rates are minimum, the group of BE seems to be the most reliable in terms of cell integrity. Key words: Sciatic nerve block, Bupivacaine, Adjuvant agent, SCN9A, TRPM.