CIRCADIAN MOTOR ACTIVITY RHYTHM OF Callithrix jacchus UNDER T CYCLES SHORTER THAN 24 HOURS

*Corresponding author e-mails: jordanabarbalho@ymail.com, crhisbio@yahoo.com.br Introduction: Some behavioral and physiological alterations are resulted from disturbances in circadian system, like metabolic syndrome and sleep disorders. Some authors suggest that the dissociation model of motor activity in rats under T22 is an excellent model to study these disturbances. Then, with the purpose to evaluate if this model can be applied to diurnal primates, we observed the motor activity of marmosets under LD cycles shorter than 24h. Methods: Motor activity of six adult females, in individual cages, was continuously registered. They were isolated in a room with controlled temperature and humidity, sound attenuated, under the symmetrical light-dark (LD) cycles T24, T21, T21.5 and T22, during 14, 60, 35 and 48 days, respectively. The light intensity during light phase was 146.5 ± 53.3 lx whereas dark phase consisted in total darkness. There were analyzed the percentage of variance (VSP) of each female motor actrivity rhythm, by Periodogram Sokolove-Bushell, and the percentage of activity during light phase. Results: Motor activity rhythm was expressed with two circadian periods under the three T cycles shorter than 24 hours: one entrained to external LD cycle, named light-entrained component (LEC) and other in free-running, named non-light-entrained component (NLEC). But all the animals presented both components only under T21. In the other two conditions, only 83.3% (T21.5) and 33.3 % (T22) of the animals showed two significative components. The value of VSP of LEC was 8.2 ± 1.1, 14.2 ± 2.5, 24.8 ± 8.0, and of NLEC was 12.0 ± 5.3, 10.9 ± 3.9, 11.9 ± 1.5 to 721, 721.5 and 722, respectively. Despite that, most of activity happened at the light phase in relation to total distribution of activity, being 86.7±4.3% (T21), 94.0±3.2% (T21.5) and 91.4±6.4% (T22). Conclusions: The occurrence of two circadian components in the motor activity of all the females under T21 is a strong evidence that this LD cycle period promotes internal desynchronization in this species. Therefore we suggest that marmosets under T21 can be a good animal model to study internal desynchronization in diurnal primates. Support: CAPES, CNPq and FAPERN Núcleo de Primatologia da UFRN — Register IBAMA: 1/24/92/0039-0 Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil