Figure 3. Light increases the open channel frequency of the NMDA receptor.

A, sample traces from an outside-out patch excised from a cortical neurone. Single channel events were activated by 3 μM NMDA. In this patch, the open channel frequency increased from 35.9 events s⁻¹ to 62.9 events s⁻¹ following a light pulse (2 s, > 280 nm). Total amplitude histograms and open time measurements in this and the other three patches revealed that light did not affect these two parameters (see Results). In this patch, the single channel conductance and open time values were 52.5 pS and 6.1 ms before the flash, and 49.7 pS and 6.4 ms following photostimulation. Scale bars: 2 pA, 20 ms. B, similar effects of light on open channel frequency were seen in a total of 4 patches which remained stable following the light stimulus (*P < 0.05, Student's two-tailed one sample t test, the null hypothesis being F_flash/F_control= 1, where F is the frequency of channel opening).