Fig. 8. DADLE did not affect the amplitude of membrane currents induced by glutamate applied microiontophoretically in the presence of TTX. (A ) Membrane inward currents induced by glutamate application (1 s, bars indicate application period) in the absence (control) and presence of DADLE. Recordings were taken in the presence of TTX (0.6–1.2 μm). The membrane potential was clamped to −70 mV. DADLE did not affect the amplitude of the glutamate-induced currents (see superimposed recordings, right ). (B ) Summary of similar experiments performed in different neurons (n = 6). Absolute values of the holding current (upper ) and the amplitudes of the glutamate-induced current (lower ) were plotted as a function of recording time. In each neuron DADLE was applied for 15 min after a control period of 15 min. The opioid peptide did not affect the holding current and the amplitude of the glutamate-induced inward current. (C and D ) Glutamate-induced inward current consisted of both an NMDA and an AMPA receptor–mediated component. This was demonstrated by the application of D-2-APV (C ) and CNQX (D ), respectively. Calibration in (D ) corresponds also to recordings depicted in (C ).