Fig. 1.
Retinal waves in normal mice are mediated by nAChRs containing α3 and β2 subunits. A, Time evolution of a single retinal wave visualized with fluorescence imaging. Decreases in fura-2 fluorescence associated with the increased calcium evoked by waves are shown at successive 0.5 sec intervals. Thelast frame represents the “domain” of the wave, defined as the total area of tissue covered by a single wave.B, Spontaneous activity is blocked by toxins specific to nAChRs containing the α3 subunit. Left, Effects of 50–100 μm curare (CUR), 2 μm dihydrobetaerthroidine (DBE), and 200 nm α-bungarotoxin (BTX) on the fractional change in fluorescence, ΔF/F, averaged over 100 μm2 regions of P0–P6 retinas.Right, Effects of α-conotoxin-AU1B (AU1B) and α-conotoxin MII (MII) on the number of waves per minute per square millimeter. The collagenase treatment necessary for peptide penetration restricted wave propagation (see Materials and Methods) and made ΔF/F measurements in a small region a poor reflection of the overall activity level. Therefore, the conotoxin effects on wave activity were measured by counting the number of waves observed in the total imaged area in a 10 min period. Scale bar, 100 μm.