Effects of local anesthesia on persistence of peripherally induced postural asymmetries in rats.

Abstract

Hindlimb flexion induced by direct stimulation of the hindlimb has been observed subsequent to spinal section if an appropriate time interval was allowed to elapse between onset of flexion and spinal cord section. The present series of experiments was conducted to test the possibility that asymmetry persistence is a product of ongoing cutaneous input that continues after stimulation offset and spinal cord section. A local anesthetic (lidocaine) was injected in the general area of stimulation, and its effects on asymmetry were assessed in three experiments. The results generally indicated that ongoing cutaneous input was not a sufficient explanation for persistence of flexion in animals stimulated with intact or severed spinal cords. The data revealed, however, that ongoing cutaneous input may partially explain results of a previous study that employed a "stimulation-wait" preparation to obtain peripherally induced spinal fixation.

Long-lasting alterations of postural asymmetry induced by cerebellar lesion and stimulation in rats

“…The observation that cerebellar lesion-induced postural asymmetry outlasts spinal cord section and dorsal rhizotomy provides additional evidence that neural alterations responsible for maintaining a fixated asymmetry occur at the spinal cord level. This finding is consistent with recent studies that have demonstrated lack of involvement of neuromuscular junctions (Steinmetz, Cervenka, et aI., 1982) or cutaneous receptors (Steinmetz, Beggs, Lupica, & Patterson, 1983) in retention of peripheral stimulation initiated fixation. It is possible that feedback from muscle afferents is required during the postlesion waiting period to produce, but not maintain, centrally initiated fixation.…”

Fixation of spinal reflex alterations in spinal rats by sensory nerve stimulation.

“…Experiment 1 provides direct evidence for this assertion. In a recent study, poststimulation thigh skin injections of a local anesthetic failed to disrupt a fixated hindlimb asymmetry, a result suggesting a lack of participation by cutaneous receptors in prolonging the fixation effect (Steinmetz et al, 1983). Potential involvement of cutaneous receptors during stimulation was eliminated in the present preparation by using direct sensory nerve stimulation and thus demonstrating that cutaneous receptors do not participate in either formation or maintenance of a fixated muscle contraction.…”

“…Experiment 1 Steinmetz, Beggs, Lupica, and Patterson (1983) recently demonstrated that ongoing sensory input from cutaneous sensory receptors was not necessary for maintaining a fixated asymmetry in spinal rats. In that study, local anesthetic (lidocaine) injected into the thigh skin after stimulation failed to block the poststimulation display of flexion.…”