440 Purinergic Signalling (2010) 6:429–445 Fig. 8 Impact of the telencephalic purinergic system on the immediate processing of olfactory information in OB cells. a Schematic represen- tation of a nose–brain preparation of larval X. laevis. The black rectangle indicates the area of the telencephalon monitored in the Ca2+ imaging experiments. b The mean response (±SEM) of all responsive cells of an OB (n=45 cells) upon epithelial application of an odorant mixture (15 amino acids, each at 100 μM; see “Materials and methods” section) was not affected by continuous OB stimulation with 5 μM 2MeSATP (b1, upper row). Compare the trace in the gray-shaded area (amino acid-induced responses after 10 min of 2MeSATP perfusion) with the traces to its left (amino acid-induced responses prior to 2MeSATP perfusion) and right (amino acid-induced responses after 5 min washout of 2MeSATP). The lower row of b1 shows the amino acid-induced [Ca2+]i transient of a randomly chosen individual cell of the same slice. Also, the mean response (± SEM) of all amino acid- responsive cells of an OB (n=23 cells) was not affected by continuous OB stimulation with 100 μM ATP (b2). Compare the trace in the light red-shaded area (amino acid-induced responses after 10 min of ATP perfusion) with the traces to its left (amino acid-induced responses prior to ATP perfusion) and right (amino acid-induced responses after 5 min washout of ATP). Prolonged application of 200 μM suramin did also not disrupt the mean response (±SEM) of all amino acid-responsive cells of an OB (n=35 cells; b3). Compare the trace in the yellow-shaded area (amino acid-induced responses after 5 min of suramin perfusion) with the traces to its left (amino acid-induced responses prior to suramin perfusion) and right (amino acid-induced responses after 5 min washout of suramin). c The mean peak responses (±SEM), expressed as percent of control response to an epithelial application of 100 μM amino acid mixture (200 OB cells from four nose–brain preparations) in control conditions (dark gray columns) and after 5 to 10 min in bath solution with 5–20 μM 2MeSATP (light gray column) are shown in c . The 1 mean peak responses ± SEM, expressed as percent of control response to an epithelial application of 100 μM amino acid mixture [78 OB cells/ 5 slices for ATP (100 μM) and 81 OB cells/4 slices for suramin 200 μM)] in control conditions (dark gray columns) and after 5 to 10 min in bath solution with ATP or suramin (light red and yellow column) are respectively given in c2 and c3. Abbreviations: OE olfactory epithelium, ON olfactory nerve, OB olfactory bulb, AA amino acid mixture that proliferating cells actively incorporate BrdU [24]. Therefore, the location of BrdU-positive cells allowed an identification of the approximate borders between the two regions (see Fig. 2). We thereby chose an adequately long time window to stain enough cells in the PVZ, but not long enough to permit stained cells to migrate into the OB. Remarkably, more than 40% of the cells within the PVZ were BrdU-positive 24 h after the injection of BrdU. This