Electrical stimulation of the rat lumbar spine induces reflex action potentials in the nerves to the lower abdomen

Study Design.The distribution of the nerve action potentials reflexively el icited by electrical stimulation of the lumbar was investigated in rats. Objectives. To elucidate the relation between the lumbar spine and other bo dy regions that compose the sinal reflex. Summary of Background Data. The hypothesis was that the ventral portion of the L5-L6 disc spatially corresponds to the groin. Methods. In Experiments 1 and 2, wire electrodes were placed 1) in the vent ral and dorsal portions of the facet joint, and muscle fascia at L5-C6, and 2) in the ventral portions of L3-L4, L4-L5, L5-L6, and L6-S discs. A needl e electrode was inserted in the L5-L6 disc by 0.4-mm increments, and action potentials were serially recorded from the genitofemoral nerve. Results. Experiments 1 and 2: Reflex action potentials were elicited in the iliohypogastric (T13 and L1), ilioinguinal (L1), and genitofemoral (L2) ne rves. Experiment 1: significantly more frequently than stimulation of the f acet joint and muscle fascia. Experiment 2: The more cranial the stimulated , the more frequently the reflex discharge induced in the iliohypogastric n erve. Experiment 3: The depth of stimulation did not influence the size of the reflex action potential. Conclusions. Electrical stimulation of the lumbar disc and facet joint indu ced reflex discharges in the nerves to the lower abdominal regions. It was postulated that the reflex discharges are related to muscle contraction res ulting in referred pain referred pain in the loin and groin.