Chloride enters glial cells and photoreceptors in response to light stimulation in the retina of the honey bee drone

Coles, J. A., Orkand, R. K. and Yamate, C. L. (1989) Chloride enters glial cells and photoreceptors in response to light stimulation in the retina of the honey bee drone. Glia, 2(5), pp. 287-297. (doi: 10.1002/glia.440020502)

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Double-barrelled ion-selective microelectrodes were used to measure free [Cl−] in photoreceptors, extracellular space, and glial cells in superfused slices of drone retina. Tests indicated that with normal superfusate the intracellular electrode signal was due essentially to Cl− and not to some other interfering anion. The results indicate that Cl− is more concentrated in both photoreceptors and glial cells than would be predicted for a passive electrochemical distribution. When the photoreceptors were stimulated by a standard train of 20 ms flashes, 1/s for 90 s, their intracellular free [Cl−] (Cli) rose by 8 ± 1 mM. At the end of stimulation Cli usually continued to rise for up to a further 2 min and then returned toward the baseline over about 10 min. During light stimulation Cli in the glia rose. The magnitude of the increase was 5.1 ± 0.4 mM, about half the increase in Ki. In some extracellular recording sites, light stimulation caused [Cl−] to increase and in others to decrease. The mean change was –0.7 mM, SD 6.5 mM. The Cl− that entered the photoreceptors and the glia was presumably made available by the shrinking of the extracellular space. When the cells were depolarized by increasing [K+] in the superfusate from 7.5 mM to 18 mM, Cli increased. The half-time of the change in Cli was longer than the half-time of the depolarization by 10–30 s in the glia and 50–250s in the photoreceptors. During superfusion with 0 Cl− Ringer's solution, the light-induced rise in extracellular [K+] was greater by a factor of 1.4–2.7, and the clearance after the end of the stimulation was slower. The rate of increase in glial Ki during light stimulation fell; the rate of increase of glial Ki caused by superfusion with raised [K+] (in the absence of Cl−) fell more. We conclude that when extracellular [K+] is increased, entry of Cl− into the glia is necessary for part, but not all, of the net uptake of K+. During light stimulation, the observed movement of Cl− into glia contributes to homeostasis of extracellular [K+], and the cell swelling associated with movement of Cl− into both glia and photoreceptors contributes to homeostasis of extracellular [Na+].

Item Type:Articles
Glasgow Author(s) Enlighten ID:Coles, Dr Jonathan
Authors: Coles, J. A., Orkand, R. K., and Yamate, C. L.
College/School:College of Medical Veterinary and Life Sciences > Institute of Infection Immunity and Inflammation
Journal Name:Glia
ISSN (Online):1098-1136

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