Conduction processes in the nerve cord of the moth Manduca sexta in relation to its ultrastructure and haemolymph ionic composition.

摘要: 1. Connectives of the ventral nerve cord Manduca sexta consist glia-ensheathed axons surrounded by a perineuriurn and an acellular neural lamella, which is greatly expanded on dorsal surface. The glial cells are linked to one another desmosomea tight junctions; latter also occur between adjacent perineurial cells. There no continuous circum-neural fat-body sheath. 2. A ten-fold change in external potassium concentration results 43 mV resting potential de-sheathed connectives. Action potentials such exposed rapidly blocked low-sodium or sodium-free saline under these conditions neither calcium nor magnesium able maintain conduction. Spikes from preparations abolished exposure 10 -6 M tetrodotoxin. These iindmgs indicate conventional ionic basis excitation for axonal membrane this insect. 3. Analyses haemolymph reveal mean sodium 25.4 (s.E. ± 0.98) mM/1 25.1 1.74) mM/.1 4. recorded sheathed connectives maintained extended periods saline. 5. Exposure most elevated concentrations two-stage depolarization. rapid, single-stage, apparently extraneuronal is, however, observed some preparations. 6. presence peripheral barrier movements potassium; junctions considered be possible sites restriction.