FIGURE 1. Morphology of taste buds (rat).

a, Viable bud isolated from the vallate papilla. Taste pore at the upper left (arrow). Length of bud is 30 m. b, Cut-open view of a bud (cartoon). Highlighted are two receptor cells with apical microvilli and basolateral synapses. c, Images of a viable bud from the vallate papilla, taken with a 2-photon microscope. The four optical planes depict multiple bipolar cells in different states of loading with a fluorescent dye, and nerve fibres. d, Three-dimensional reconstruction, from microscopic serial sections, of a bud from the foliate papilla, the taste pore facing upwards. On the left, a solitary bipolar cell with innervating nerve fibre is also visible. Scale bar, 25 m. (Image courtesy of V. I. Popov, Institute of Cell Biophysics, RAS, Pushchino, Russia.). e, Bipolar receptor cell with sensory nerve fibre attached. Some morphological details and the location of the main types of identified ion channels on the lateral membrane are indicated. BP, basal cell process.