Fig. 6. Effect of dnqx on excitation of cell Tr1 by p cell. a. In normal physiological saline, intracellular stimulation of the P cell evokes a barrage of action potentials in cell Tr1. CALIBRATION: 10 mV, 1 s. b. Control: In high divalent saline, 3 action potentials (denoted by *) elicited in a P cell by intracellular current injection result in summation of 3 EPSPs in cell Tr1. DNQX: Exposing the nerve cord to saline containing 50 mM DNQX almost completely eliminates the P cell-induced EPSPs in cell Tr1. Each trace represents 10 averaged signals. The tops of P cell action potentials are clipped. CALIBRATION: 20 mV (P cell) and 1 mV (cell Tr1), 100 ms.