Emulsified isoflurane increases convulsive thresholds of lidocaine and produces neural protection after convulsion in rats

In relation to NO-System, Stable Pentadecapeptide BPC 157 Counteracts Lidocaine-Induced Adverse Effects in Rats and Depolarisation In Vitro

Recently, the pentadecapeptide BPC 157-induced counteraction of bupivacaine cardiotoxicity has been reported. Medication includes (i) lidocaine-induced local anesthesia via intraplantar application and axillary and spinal (L4-L5) intrathecal block, (ii) lidocaine-induced arrhythmias, (iii) convulsions, and (iv) lidocaine-induced HEK293 cell depolarisation. BPC 157 applications (intraplantar, intraperitoneal, and intragastric) were given (i) immediately after lidocaine, (ii) 10 min after, or (iii) 5 min before. The BPC 157/NO-system relationship was verified with NO-agents, the NOS-blocker L-NAME and the NOS-substrate L-arginine, given alone and/or together, in axillary and spinal intrathecal blocks. BPC 157 applied immediately after lidocaine or 5 min before the application of lidocaine considerably ameliorated plantar presentation. BPC 157 medication considerably counteracted lidocaine-induced limb function failure; L-NAME was counteracted; L-arginine exhibited counteraction when given immediately after lidocaine, but prolongation was seen when given later. Given together, prophylactically or therapeutically, L-NAME and L-arginine (L-NAME + L-arginine) counteracted the other's response. BPC 157 maintained its original response when given together with L-NAME or L-arginine. When BPC 157 was given together with L-NAME and L-arginine, its original response reappeared. BPC 157 antagonised the lidocaine-induced bradycardia and eliminated tonic-clonic convulsions. Also, BPC 157 counteracted the lidocaine-induced depolarisation of HEK293 cells. Thus, BPC 157 has antidote activity in its own right against lidocaine and local anesthetics.

Emulsified isoflurane combined with therapeutic hypothermia improves survival and neurological outcomes in a rat model of cardiac arrest

Emulsified isoflurane (EIso), when introduced following cardiopulmonary resuscitation (CPR), significantly improves survival and neurological outcomes in a rat model of cardiac arrest (CA). The present study aimed to examine whether EIso combined with therapeutic hypothermia (TH) confers an additive neuroprotective effect. Adult male Sprague-Dawley rats that were subjected to return of spontaneous circulation (ROSC) after a 6-min asphyxia-induced CA were randomized to five groups: Sham group, control group under normothermic conditions, EIso group (4 ml/kg for 30 min under normothermic conditions), TH group (33°C for 2 h), and EIso plus TH group. Survival conditions and neurological outcomes were evaluated at 1 day and 7 days after ROSC. Animal survival rate at 7 days after ROSC was 30.7% in the CPR group, 60% in the EIso group, 63.6% in the TH group and 72.7% in the EIso plus TH group. EIso, TH and EIso plus TH yielded significant improvements in survival rates, neural deficit score and cognitive function, and ameliorated hippocampal CA1 region cell injury and apoptosis at 1 day and 7 days after ROSC compared with the CPR group. Combined therapy of EIso and TH was superior to EIso or TH alone, suggesting that combined EIso and TH treatment results in significant improvements in survival and neurological outcomes, and was more effective than independent EIso or TH treatment.

The quaternary lidocaine derivative QX-314 produces long-lasting intravenous regional anesthesia in rats

Background

The lidocaine derivative, QX-314, produces long-lasting regional anesthesia in various animal models. We designed this study to examine whether QX-314 could produce long-lasting intravenous regional anesthesia (IVRA) in a rat model.

Methods

IVRA was performed on tail of rats. EC₅₀ (median effective concentration) of QX-314 in IVRA was determined by up-and-down method. IVRA on tail of rats was evaluated by tail-flick and tail-clamping tests. For comparison between QX-314 and lidocaine, 60 Sprague-Dawley rats were randomly divided into 6 groups (n = 10/group), respectively receiving 0.5 ml of 0.5% lidocaine, 0.25% QX-314, 0.5% QX-314, 1.0% QX-314, 2.0% QX-314 and normal saline. To explore the role of TRPV1 channel in IVRA of QX-314, 20 rats were randomly divided into 2 groups (n = 10/group), respectively receiving 0.5 ml of 1% QX-314 and 1% QX-314+75 µg/ml capsazepine. Toxicities of QX-314 on central nervous system and cardiac system were measured in rats according to Racine's convulsive scale and by electrocardiogram, respectively.

Results

QX-314 could produce long-lasting IVRA in a concentration-dependent manner. EC₅₀ of QX-314 in rat tail IVRA was 0.15±0.02%. At concentration of 0.5%, IVRA duration of QX-314 (2.5±0.7 hour) was significantly longer than that of 0.5% lidocaine (0.3±0.2 hour, P<0.001). TRPV1 channel antagonist (capsazepine) could significantly reduce the effect of QX-314. For evaluation of toxicities, QX-314 at doses of 5 or 10 mg/kg did not induce any serious complications. However, QX-314 at dose of 20 mg/kg (1% QX-314 0.5 ml for a rat weighing 250 g) induced death in 6/10 rats.

Conclusions

QX-314 could produce long-lasting IVRA in a concentration-dependent manner. This long-lasting IVRA was mediated by activation of TRPV1 channels. Evaluation of toxic complications of QX-314 confirmed that low but relevant doses of QX-314 did not result in any measurable toxicity.