| Abstract: | The effects of exogenously added phospholipase A2 (PLA2) and its hydrolytic products in isolated bullfrog sciatric nerve were investigated. Nerves were pretreated for 3 h with a dose of trypsin which did not affect conduction in order to enhance penetration of the added agents. Threatment of nerves with β-glucosidase, neuraminidase or chymotrypsin had no effect on conduction. Whereas incubatin of the nerves with normal Ringers for 2 h had no significant effect on conduction, incubation with PAL2 in Ringers caused decrements in the height of the compound action potential in dose-related manner. In addition, incubation of the nerves with 10 mg/ml lysolecithin, arachidonic acid, or docosahexaenoic acid caused marked decrements in the height of the compound action potential. Electron microscopic analysis of nerves after each treatment which caused conduction block revealed varying levels of myelin damage. Although myelin was damaged at the paranodal and/or internodal region, depending on the agents used, the axonal membrane appeared to be intact at the ultrastructural level. It was concluded that the block in conduction resulting from PLA2 was due to the formation of lysolecithin and long chain polyunsaturated fatty acids. |
