Responses of isolated white perch horizontal cells to changes in the concentration of photoreceptor transmitter agonists

Current and voltage responses elicited by increasing or decreasing the concentration of l-glutamate or its analog kainate around isolated cone horizontal cells were measured with patch pipettes using the whole cell recording configuration. Application of these photoreceptor transmitter agonists induced inward currents in voltage-clamp experiments (for negative holding potentials) and depolarizing responses in current-clamp experiments. Continuous exposure to either drug produced inward currents which were maintained for as long as superfusion with the drugs continued. Reducing the concentration of the agonists by pressure ejection of pulses of drug-free Ringer's solution onto the cells completely turned off the drug-induced currents. Under current-clamp conditions, pulses of control Ringer's elicited hyperpolarizing responses of large amplitude (40-80 mV). The data demonstrate the ability to stimulate in vitro the horizontal cell's photoresponses and thus support the use of cultured cells as a model system for studying horizontal cell physiology and pharmacology.