Effect of circadian phase on context and tone fear conditioning in C57BL/6J mice

VALENTINUZZI VS; KOLKER DE; VITATERNA MH; FERRARI EAM; TAKAHASHIJS; TUREK FW

ANIMAL LEARNING & BEHAVIOR

Psychonomic Society, Inc

Lugar: Austin; Año: 2001 vol. 29 p. 133 - 142

0090-4996

We examined context-dependent and tone-cued fear conditioning during the activity and rest periods of C57BL/6J mice. Wheel-running activity was measured constinuously as a marker of circadian phase. To control de effects of light on the response, the animals were kept in a skeleton photoperiod (two 15-min light pulses per day, indicating the beginning and the end of the day). Half the animals were trained and tested for context-dependent fear conditioning 2 h after the morning light pulse; the other half were trained and tested 2 h after the evening light pulse. Animals were tested every 24 h for five days to analyze the conditioned response and the rate of extinction. They were then trained for tone-cued fear conditioning at the same time and tested for five consecutive days. A significant difference between the morning and the evening groups was observed for the conditioning level and the extinction rate of context-dependent fear conditioning, but not in tone-cued fear conditioning.These results suggest a modulating effect of the biological clock on the context fear conditioning pathway.