The depth profile of electrically induced tectal sustained potential shift responses in the goldfish (Carassius...

Tectal sustained potential shifts (SPSs) were recorded in response to electrical stimulation of the tectal surface in immobilized goldfish using saline-filled glass microelectrodes. The peak amplitudes of surface recorded SPS responses were negative, this negativity declining with increasing tectal depth, reversing in polarity at a depth of ca. 350 microns and subsequently increasing in positivity. These opposing SPS polarities are attributed to field potentials generated by the source and sink of extracellular K+ ([K+]e) redistribution through a functional syncitium of radially connected glia.