Protein kinase C does not mediate the dopamine-dependent modulation of glutamate receptors in retinal horizontal cells of the perch (Perca fluviatilis)

The whole-cell patch-clamp technique was employed to record membrane currents from cultured horizontal cells of the perch (Perca fluviatilis). The cells were voltage clamped and slowly superfused with an extracellular solution containing L-glutamate. The glutamate concentration in the bath was continuously measured with the help of photodiode and a dye which accumulated in the bath together with the agonist. The PKA-activator forskolin mimicked the effect of dopamine and enhanced glutamate-induced currents, while application of the PKC stimulator PMA or the synthetic diacylglycerol analogue OAG had no significant effects on the dose-response curves of glutamate induced-currents. These results may indicate that the modulation of glutamate receptors in fish horizontal cells is not mediated via a PKC-dependent pathway.