Effects of some Ca2+ blockers on receptor potentials of crayfish retina.

One drug known to inactivate calmodulin and two others to block Ca2+ channels were applied to isolated superfused retinae of the crayfish Astacus leptodactylus and their influence on the receptor potentials (RP) was studied. Trifluoperazine causes an increase of the amplitude of maximum (h max) of RP and a prolongation of the time of half decrease (t2). Furthermore, trifluoperazine could antagonise the effect of raised calcium concentration of superfusate, which decreases h max and shortens t2 of the RP. Iproveratril and D-600 cause a transient increase and thereafter a progressive decrease of h max of the RP. There is a difference between effects of both drugs on t2 of the RP. The mechanisms of effects of these drugs on the sensitivity of the isolated retina are discussed.