Behavioral and electrophysiological estimates of visual thresholds in awake rats treated with 3,3 ',4,4 ',5-pentachlorobiphenyl (PCB 126)

Visual thresholds for luminance increments were obtained behaviorally and e lectrophysiologically from rats exposed to a polychlorinated biphenyl (PCB) during development. Male Long-Evans rats exposed to 0, 0.25, or 1.0 mu g/k g/day of 3,3',4,4',5-pentachlorobiphenyl (PCB 126) through gestation and we aning were trained as adults to perform a signal detection task. Estimates of threshold were derived from psychometric functions for each animal relat ing the proportion of hits to signal intensity. Thresholds derived under th ree luminance conditions did not differ significantly among the PCB-treated groups. After behavioral testing was completed, flash-evoked potentials we re recorded from dark-adapted awake animals. Peak amplitudes increased line arly over approximately 3 log units of intensity. Extrapolations to 0 ampli tude along the linear portion of the amplitude-log intensity functions prod uced estimates of absolute threshold of -5.44 to -5.53 log cd/m(2)-s. Wavef orms recorded from awake animals had a large late negative component that w as absent in previously reported anesthetized preparations. Developmental e xposure to PCB 126 had no significant effect on absolute threshold or peak amplitudes and latencies. (C) 2000 Elsevier Science, Inc. All rights reserv ed.