POTASSIUM CHANNELS ACTIVATED BY GABA(B) AGONISTS AND SEROTONIN IN CULTURED HIPPOCAMPAL-NEURONS

1. Single-channel currents were recorded in cell-attached patches on c ultured hippocampal neurons in response to gamma-aminobutyric acid-B ( GABA(B)) agonists or serotonin applied to the cell surface outside the patch area. 2. The channels activated by GABA, agonists and serotonin were potassium selective but had a different conductance and kinetic behavior. Channels activated by GABA, agonists had a higher conductanc e, longer open-time, and longer burst-length than channels activated b y serotonin. 3. The kinetic behavior of channels activated by GABA, ag onists varied with potential whereas channels activated by serotonin d id not show voltage-dependent changes in kinetics. 4. In a few cell-at tached patches, both types of channel were activated when the cell was exposed to GABA together with serotonin. 5. It was concluded that GAB A, agonists and serotonin activate different potassium channels in the soma of cultured hippocampal neurons.