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Diurnal variation of behaviour
and habituation in pigeons: correlations with rhythms of plasmatic
melatonin and corticosterone C. M. Z. Souza, A. A. M. Rosa e Silva, M. C. S. Caldas, V. S. Valentinuzzi and Elenice A de Moraes Ferrari Universidade Estadual de Campinas, Brasil This work analyzed the diurnal variation of behaviour and habituation of the exploratory response to tone along the 24h of the day. In Experiment I, behaviour was video-taped at 3, 6, 9, 12, 15,18, 21 and 24h. One group was under a 12:12h light-dark cycle (LD) and another had constant light (LL). Blood samples were obtained every 3 hours. Radioimmune essays evaluated plasmatic melatonin and corticosterone. Experiment II analyzed habituation of exploration to sound (1000-Hz, 83dB, 1s). LD and LL birds were subdivided in 8 groups, each one tested at a different time. LD data showed a rhythm of melatonin with high melatonin during the dark. Diurnal variation of behaviour showed peaks at 6h, 12h and 18h. Under LD habituation occurred only during the day. Habituation occurred at every time under LL, except at 21:00 and 24:00h. Higher LL values of median plasma corticosterone indicated constant light as stressful. This change in corticosterone added to the blunting of the melatonin rhythm in LL may affect the diurnal variation of behaviour and habituation. The data relate to the interrelationships between oscillatory biological systems and the circadian timing of activity and learning. Keywords: habituation, behavioural rhythms, melatonin, corticosterone, pigeons |
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