Marmosets Under T21: A Primate Model for Forced Desynchronization

*Corresponding author e-mail: crhisbio@yahoo.com.br Introduction: The suprachiasmatic nuclei (SCN) are the master structure of mammalian circadian system. There are lots of evidences that each SCN cell is an oscillator and that entrainment depends upon coupling degree between them. Knowledge of this coupling mechanism is essential to understand entrainment and expression of circadian rhythms, which will help to provide the development of new treatments to circadian rhythms sleep disorders (CRSDs). Some authors suggest that the dissociation model of circadian rhythm activity of rats under T22 is a good model to induce internal desynchronization, and in this way, enhance knowledge about the coupling mechanism. So we applied the dissociation model to marmosets in order to find a primate model for forced desynchronization. Methods: With this purpose 6 adult females were kept in individual cages, in a room with controlled temperature and humidity, and sound attenuated. The light intensity during light phase was 146.5 ± 53.3 lx whereas dark phase consisted in total darkness. They were maintained under the symmetric light-dark (LD) cycles T 21, T 21.5 and T 22 during 60, 35 and 48 days, respectively. Motor activity of each animal and vocalizations of all animals were continuously registered. Results: Two components of circadian motor activity rhythm were seen for all animals under T21, one with the same period of external LD cycle, named light-entrained component (LEC), and the other in free-running, named non-light-entrained component (NLEC). In the other two conditions, only 83.3% (T21.5) and 33.3 % (T22) of the animals showed two significative components. For vocalizations there were observed two circadian components under the three LD cycles periods. These results reflect the activity of at least two different groups of oscillators, being one capable of entrain to the LD cycle while the other can’t, depending on LD cycle period. This probably occurred due to an uncoupling between these oscillators inducing an internal desynchronization. Conclusions: Therefore, as all the animals presented two circadian components in motor activity and vocalizations rhythms only under T21, we suggest that marmosets under T21 can be a good primate model to study internal desynchronization. An animal model with a diurnal primate can be very useful to the development of new treatments to CRSDs, since most of the animal models are with nocturnal rodents. Support: CAPES, CNPq and FAPERN Núcleo de Primatologia da UFRN — Register in 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