Fig. 1.

Neuronal domains in fura-2-stained slices in neonatal rat visual cortex. Slices were illuminated with 385 nm light at which fura-2 emission decreases with increasing calcium concentration. Video images were taken before (left) and during (middle) the occurrence of neuronal domains. On the right, the changes in the fura-2 fluorescence are expressed in pseudocolor as ΔF/F (in percent) and overlaid onto the images shown in themiddle. Each individual image is the average of 16 background-subtracted single frames taken at video rate. The pial surface is indicated by the arrowheads; the white matter is identified by the dashed line. A, Neuronal domains elicited by temperature drop under control conditions (2 μm TTX). Coronal slice of a P3 rat. B, Neuronal domains elicited by temperature drop in the presence of 2 mm Ni²⁺ and 2 μm TTX. These neuronal domains are similar in size and shape to those observed under control conditions, indicating that neither sodium-dependent action potentials nor extracellular Ca²⁺ entry is required for the occurrence of neuronal domains. Coronal slice of a P2 rat.