Light-induced changes in extracellular volume in the retina of the drone, <i>Apis mellifera</i>

Slices of drone retina were superfused with a Ringer solution containing 1 mM tetraethylammonium (TEA), and the concentration of this ion in the extracellular space ([TEA]0) was measured with ion-sensitive microelectrodes. A train of light flashes for 90 s caused [TEA] to increase by 48 ± 4% (S.E.), n = 12. Since water crosses cell membranes more readily than TEA does this indicates a volume decrease of at least 32%. Measurements of Ca2+ activity under similar conditions showed an increase of 32 ± 4% (S.E.), n = 14. Since this is less than the increase in [TEA]0 it suggests that the total amount of Ca2+ in the extracellular space actually decreased

Nitric oxide sensitive depolarization-induced hyperpolarization: a possible role for gap junctions during development

Electrical coupling is a widespread feature of developing neuronal circuits and it contributes to the generation of patterned activity, In the developing rat hippocampus, release of GABA by coactive hilar interneurones generates widespread synchronized activity, Here it is shown that hilar interneurones strongly rectify in the outward direction when depolarized, This depolarization-induced hyperpolarization, abolished by gap junction uncouplers, is modulated by nitric oxide, This phenomenon might represent a current-shunting mechanism of the excess current by providing functional inhibition at a developmental stage when GABA is excitatory, Spatial buffering of the current might represent an osmotic mechanism for growth and differentiation