- A systemic exposure to gram negative LPS have caused transient conduction abnormalities in a certain strain of rats probably associated with the action of cytokines secreted by macrophages. Our previous studies demonstrated that anti-GM1 antibodies induced in rats by the cross-reactive Cj-LPS, caused no conduction abnormalities. We designed the present study to evaluate the effect of systemic exposure to Cj-LPS on nerve conduction after a focal minor neural trauma. Female Lewis rats were sensitized against KLH by repetitive subcutaneous injections. After 28 days rats were intraneurally injected with saline in the right sciatic nerve and concomitantly with intraperitoneal Cj-LPS. Sciatic nerve conduction studies were performed on days 0, 1, 2, 3, and 7 after injections. Nerve conduction blocks developed in all the rats ( n =10) which received an intraneural injection of saline concomitantly with the systemic Cj-LPS exposure, before titers of anti-ganglioside antibodies were detected. We conclude that humoral factors (possibly cytokines), other than antibodies are secreted by lymphocytes and macrophages stimulated by gram negative LPS, and cause functional conduction abnormalities when the blood–nerve barrier is disrupted.