The Electrophysiological Effects of Lithium in the Rat

Abstract

The effects of lithium on the tail nerve conduction velocity of the rat were studied. No effect of lithium on the conduction velocity was found, even at toxic serum lithium levels. No effect of lithium on repetitive stimulation of the distal forelimb flexor muscles was seen. The results suggest that electrophysiological measurements do not provide an effective means of titrating serum lithium levels in the rat. The results may have clinical significance since they provide evidence against neuropathic or neuromuscular transmission defects as the cause of the transient weakness of some patients taking lithium.

Effects of Lithium on Rat Tail Nerve Conduction Velocity

“…The antidromic response, on the other hand, mainly reflects conduction in centrifugal fibers and thereby corresponds primarily to transmission in sensory nerves. It is to be noted, however, that the orthodromic and antidromic responses in the rat tail nerve are not completely identical to conduction in motor and sensory nerves, respectively [11], The conduction velocity measured by the orthodromic response in our control rats was similar to the motor nerve conduction velocity reported by Samples and Seybold [9] and by Miyoshi and Goto [7] in rats of the same age as ours. However, the velocity of antidromic response in our control rats was lower than the sensory nerve conduction velocity measured by Samples and Seybold [9].…”

“…Samples and Seybold [9] failed to find alterations in conduction veloc ity in their study on the effects of lithium in the peripheral nerves of rats. Their animals received lithium for 2 weeks and showed polyuria without signs of neuromuscular disturbances at the time of testing.…”

“…The occurrence of neuromuscular disorders during lithium therapy makes the actions of lithium on peripheral nerves of interest. A previous study in humans showed lithium administration to reduce the conduction velocity in peripheral nerves [5], while a study in laboratory animals failed to find effects of lithium on nerve conduction velocity [9]. The present study was carried out to investigate further effects of lithium on conduction veloc ities in peripheral nerves.…”

“…Nerve conduction velocity was measured between 4 and 7 p.m. following the meth ods of Miyoshi and Goto [7] and Samples and Seybold [9] as shown in figure 1. The rats were anesthetized by an intraperitoneal injection of pentobarbital sodium (35 mg/kg).…”