The experience in the water maze task can affect the circadian rhythm of locomotor activity

VALENTINUZZI, VS ; PASTRANE-DINIZ G; MENNA-BARRETO L; XAVIER GF

BIOLOGICAL RHYTHM RESEARCH

Taylor & Francis

Lugar: Leiden; Año: 2007 vol. 38 p. 399 - 414

0929-1016

Wistar rats maintained in cages with running wheels and submitted to a skeleton photoperiod or to a light-dark cycle were tested in the Morris water maze. Half of the animals of each condition was exposed to the task during their active phase while the other half was exposed during their inactive phase. The effect of the experience in the water maze, a strong arousing event, on the rhythm of wheel-running activity was evaluated. In the first experiment a group of animals submitted to a skeleton photoperiod was trained every day in the reference memory version of the task. The novel experience in the water maze produced an apparent abrupt phase shift of the circadian rhythm of wheel-running activity only of the animals tested during their inactive phase. Another experiment was run but now using single working memory sessions in the water maze and with animals submitted to a light/dark cycle. The circadian rhythm of locomotor activity was evaluated in undisturbed days and compared with testing days. The experience in the water maze had a significant effect on rhythmicity despite the presence of the light-dark cycle. Changes in the phase angle of entrainment to the light-dark cycle, as well as an increase in onset variability were observed. All together, the data suggest that there is a modulating effect of the arousing experience in the pool on the overt circadian rhythm of locomotor activity.