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DIFFERENTIAL EFFECTS OF LOW CALCIUM ON SIGNAL TRANSMISSION FROM RODS AND CONES TO HORIZONTAL CELLS IN CARP RITINA

Wang Hailong, Yang Xiongli

(Shanghai Insititute of Physiology, Shanghai Joint Laboratory of Life Science, Chinese Academy of Seiences, Shahghai 200031)

Abstract

Intracellular recordings were made from neurons in the superfused isolated carpretina and the effects of calcium on synaptic transmission from cones and rods to horizontal cells were studied by changing the ionic composition of the external medium.When extracellular Ca2+ is lowered from 1. 2 mmol/L to 0. 1 mmol/L，both cone- and rod-horizontal cells (Cone-HC and Rod-HC) are depolarized，but light responsiveness of these cells are differentially affected:light responses of Cone-HCs are reduced in
size，whereas those of Rod-HCs are significantly enhanced. In 0. 1 mmol/L Ca2+，glutamate-isolated P 1Q components，both photopic and scotopic，are enhanced，suggesting that the differential effects of low calcium on the horizontal cells must occur during signal transferring from photoreceptors to horizontal cells. Similar to the effect of 0. 1mmol/L Caz+，phosphodiesterase inhibitor IBMX(5 0 pmol/ L) is also capable of enhancing light responsiveness of both L-type Cone-HC and Rod-HC. These results suggest that the differentail effects of low calcium on the two types of horizontal cells may
be due to different changes in the calcium influx into the receptor terminals.

Key words: retinal horizontal cen;Synaptic transmission;photoreceptor;calcium

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Citing This Article：

Wang Hailong, Yang Xiongli. DIFFERENTIAL EFFECTS OF LOW CALCIUM ON SIGNAL TRANSMISSION FROM RODS AND CONES TO HORIZONTAL CELLS IN CARP RITINA. Acta Physiol Sin 1996; 48 (2): (in Chinese with English abstract).