Figure 6. Data from a single neurone showing that the Group I agonist DHPG and Group I antagonist 4CPG have opposing effects on visual responses in vivo.

For details of histograms and stimuli see Fig. 1. A, DHPG inhibits visual responses: (i) control, (ii) during DHPG ejection, (iii) recovery, data obtained 120 s after DHPG ejection ceased. B, 4CPG enhances visual responses: (iv) new control, (v) during 4CPG ejection, (vi) recovery, data obtained 120 s after 4CPG ejection ceased.