A sciatic nerve blockade method to differentiate drug-induced local anesthesia from neuromuscular blockade in mice

This report introduces a simple and easy technique for animal handling and drug administration into the sciatic nerve area for determining local anesthesia and neuromuscular blocking activity in mice. The drugs were injected into the popliteal space of the right hindlimb (i.e., the sciatic nerve area). The loss of motor activity of the right hindlimb was taken as a sign of producing local anesthesia. A positive local anesthetic activity was recorded when a mouse was only able to walk using three limbs on an inverted wire mesh screen and the injected limb was hanging in the air. This method is superior to the commonly used techniques of applying drugs to the rabbit's cornea, the guinea pig's back skin, or the root of the mouse tail to determine the reduced reflex responses and to assess the local anesthetic activity. The present method has evaluated a number of drugs (cocaine, lidocaine, procaine, propranolol, quinidine, quinacrine, verapamil, and diltiazem), which are known to produce local anesthesia. The sciatic nerve blockade technique is also capable of determining neuromuscular blocking activity of drugs, in which the end point of activity taken is different from that for local anesthetic drugs. The method reported here has been validated by reference neuromuscular blocking agents (d-tubocurarine, decamethonium, and succinylcholine). A positive neuromuscular blockade was recorded when a mouse was unable to stay on the inverted wire mesh screen. The information provides not only the local anesthetic or neuromuscular blocking potency of drugs but also duration of action of drugs.