Bacterial lipopolysaccharide induces a conduction block in the sciatic nerves of rats.

A single injection of Escherichia coli lipopolysaccharide (LPS; intraperitoneally [i.p.] and intravenously [i.v.]) reliably induces peripheral nerve disturbances in the hindlimbs of inbred Australian albino Wistar (AaW) rats. In the series of experiments presented here, we aimed to characterize this syndrome by examining electrophysiologic, immunologic, and immunochemical features. The LPS-induced neurologic sequelae in AaW rats were transient, at least partly reversible by drug treatment, and were not associated with any detectable neuropathologic findings by light microscopy. Neurologic sequelae were prevented by administration of dexamethasone and by pretreatment with the macrophage inhibitor gadolinium chloride, suggesting that they were caused by LPS-induced activation of peripheral macrophages. Sequelae were associated with early decreases in compound muscle-action potential amplitudes, indicating impaired functioning of either proximal sciatic nerve axons and/or neuromuscular synapses. Spinal somatosensory-evoked potential latencies also were increased, indicating impaired somatosensory function at the sciatic nerve, dorsal roots, spinal cord, and/or postsynaptic interneurons, although the precise location of impairment could not be delineated. Similarities between this syndrome and immune-mediated polyneuropathies in humans are discussed.