Close tip-to-tip contacts between dendrites of transient amacrine cells in carp retina

In isolated retinas of the carp (Cyprinus carpio) placed receptor side up in a plastic chamber, a subclass of amacrine cells, generating a fast ON-OFF transient response to spot and annular light stimuli, were intracellularly recorded and injected with a fluorescent dye, Lucifer yellow (LY). After brief fixation of the same preparations in aldehyde solution, the retinas were wholemounted vitreous side up in a tissue chamber. Under a fluorescence microscope, one LY-injected cell and several dye-coupled cells were seen; these cells belonged to type Fnd, having a fusiform soma, narrow dendritic field and bistratified dentrites in the inner plexiform layer (IPL). To reveal the interconnections between dendrites, one of such dye-coupled cells was further injected with LY. Close tip-to-tip contacts were predominantly found between dendrites of neighboring type Fnd cells in sublaminae a and b of the IPL, respectively.