Fig. 8. Time course of the effects of Ca²⁺-free saline (A) or 10^–4 mmol l^–1 bicuculline (B) on the optical signals in the antennal lobe (AL) evoked by stimulation of the lateral nerve (LN). The optical signals were compared in five square areas (mT, cT, lT, mC and lC). The optical signals were filtered at 246 Hz (=F_c). Scale bar in real image, 100 µm. (A) The optical signals under normal saline conditions (black line) were superimposed onto those under Ca²⁺-free saline conditions (green lines). Postsynaptic activity (red lines), blocked by Ca²⁺-free saline, was evoked in both the lT and the lC (arrowheads). The peak amplitudes of the excitatory postsynaptic responses (blue lines) in the optical signals in the lT and the lC were significantly larger than those of the other macroglomerular complex (MGC) sub-regions (see text for details). (B) Optical signals blocked by bicuculline were detected in all MGC sub-regions except for the mT (double arrowheads on orange lines). The maximum amplitudes of the GABAergic inhibitory postsynaptic responses in these MGC sub-regions were not significantly different from each other.