The suitability of Melanoplus differentialis for electrophysiological investigation based on hemolymph ionic and anatomical studies

Effect of metabolic inhibition on sodium ion exchange in the ventral nerve cord of Melanoplus differentialis

“…Recent studies on M. dz@~entiuZis (Weidler et al, 1973) demonstrated a so-called tracheolated membrane or fat-body sheath in this species. Therefore, it follows from the above discussion that it is possible that the tracheolated membrane or fat-body sheath in M. d$mntialis is the site of the active Na+ absorption which was demonstrated in the present study.…”

“…Tris-HCl buffer was used to maintain the pH at 7.4, and to elevate the osmotic concentration to the desired level. Although the normal hemolymph Na+ concentration in M. diferentialis is 64.9 mM (Weidler et al, 1973), a solution containing only 15 mM Na+ was utilized in the present study to exaggerate the effect of an active Na+ uptake mechanism which might be present. In experiments where metabolic inhibition was desired, the normal physiological solution was altered by replacing 5 mM NaCl with 5 mM sodium azide (NaN,).…”

“…However, despite these defects it is clear that active Na+ absorption occurs in the nerve cords of C. morosus and D. fmorata because total uptake values are not dependent on the methods of component analysis. In the present work the effect of metabolic inhibition on Na+ absorption by the nerve cord of M. dz@mztialis was investigated; this species was selected because it has a hemolymph Na+ concentration of 64.9 mM (Weidler et al, 1973). Since M. dzj%mntiaZis has a relatively low hemolymph Na+ concentration, we hypothesize that Na ions are absorbed actively into the extracellular fluid which surrounds the neurons in the nerve cord ; such a transport mechanism would result in an elevated Na+ concentration in the extracellular fluid relative to the hemolymph, and may occur via an active transport system located in the neural sheath complex.…”