THE DEPTH PROFILE OF ELECTRICALLY INDUCED TECTAL SUSTAINED POTENTIAL SHIFT RESPONSES IN THE GOLDFISH (CARASSIUS-AURATUS)

Tectal sustained potential shifts (SPSs) were recorded in response to electrical stimulation of the tectal surface in immobilized goldfish using saline-filled glass micro-electrodes. 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 μm 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. © 1993 Academic Press, Inc.