Figure 1.

Different expression levels of EGFP fluorescence in astrocytes in the ventral respiratory group. A, B, Maximum-intensity projections of stacks of images recorded by confocal laser scanning microscopy from EGFP-expressing astrocytes in the ventral respiratory group(A) and the hypoglossal nucleus (B). In both regions, weakly fluorescent astrocytes (arrowheads) appear to have fewer processes than brightly stained cells (arrows). To visualize process extension more precisely, cells were filled during patch-clamp recording with a red fluorescent dye (Alexa Fluor 568), and confocal images were recorded after fixation. C-E, Filling of a highly fluorescing astrocyte with Alexa Fluor 568 revealed a dense process extension of several tens of micrometers (maximum-intensity projection). F, Membrane currents evoked by 100 msec voltage steps from -150 to +70 mV of the highly fluorescent astrocyte filled in C-E. G-I, Filling of weakly fluorescent astrocytes with Alexa Fluor 568 revealed a similar extension of processes, but the overall density of the processes was smaller. J, Corresponding membrane currents evoked by 100 msec voltage steps from -150 to +70 mV of the astrocyte filled in G-I. Scale bars, 20 μm.