Inhibitory effect of anisodamine on the neuropathic hyperalgesia following peripheral nerve injury (II).

A peripheral neuropathy with hyperalgesia and allodynia was produced by loosely tying constrictive ligature around the left sciatic nerve of rats, i.v. injection of anisodamine 20 mg/Kg abolished both neuropathic hyperalgesia responses to noxious radiant heat and ectopic discharges generated from the injured region of the nerve. Anisodanime applied either systemically or locally to the damaged area of the nerve not only ceased the spontaneous ectopic discharges recorded from A beta to C fibers but also blocked the afferent ectopic discharge elicited by K+ channel blocker, noradrenaline, Ca2+ or antidromic stimulation of sciatic nerve proximal to the injured nerve area. The experiments indicated that anisodamine probably possessed a calcium channel blocker-like activity and produced selective block of the new channels in the injured area. It is suggested that anisodamine may be a candidate therapeutic agent in relieving hyperalgesia and allodynia following nerve injury.