Temperature-dependent electroretinogram responses were investigated in the dark adapted bullfrog eyes within the physiological temperature range 0-40oC.
In hypothermic process (25
0
25oC), the amplitude of b- and c-wave decreased with lowering the temperature but increased with raising up to room temperature again.
Both b-wave amplitude and threshold responses were maximal around 15oC during the temperature increment.
Upon warming to room temperature again (25oC), the b-wave amplitude was approximately doubled as compared to that of control without temperature changes.
During the hyperthermic process (25
40
25oC), however, the responses decreased with warming, and the wave amplitude failed to recover by cooling to 25oC again.
As described above, the recoveries of ERG in both processes show the striking difference.
The hypothermia induces the amplification of the b-wave, that is, enhances the retinal function with the temperature recovery toward room temperature.
While the hyperthermia produces the decrease of the b-wave even though recovered to room temperature, which indicates an irreversible retina.
The morphological alteration is shown both hypothermic and hyperthermic process, such as an appearance of large vacuoles and degenerating outer segments, more intense in hyperthermia, similar to light induced damage.