Kainic acid-induced release of serotonin from OFF-bipolar cells in the turtle retina

The immunofluorescence of antibody-labelled serotonin was used as an indicator for the amount of intracellular serotonin. Incubation in Ringer solution containing serotonin and pargyline increased the immunofluorescence which was subsequently decreased in a calcium-dependent manner by incubation in high-potassium Ringer. If preloaded retinas were exposed to 10 microM kainic acid, the immunofluorescence decreased in a time-dependent way. This kainic acid-induced release was blocked by piperidine dicarboxylic acid. These results support the idea that serotonin is a transmitter in OFF-bipolar cells.