ALERT STATE IN Callithrix jacchus UNDER LIGHTDARK CYCLES SHORTER THAN 24 HOURS

*Corresponding author e-mail: laisbmm@gmail.com, crhisbio@ yahoo.com.br Introduction: Some quotidian situations, like summer time, shift work, among others, promote desynchronization among the endogenous oscillators that can lead to disturbs in circadian rhyhtmicity. These disturbs can generate diseases, including circadian rhythms sleep disorders. Some authors suggest that the dissociation model of rats under T22 is a good model to force internal desynchronization. Then, in order to find a primate model of internal desynchronization we evaluated the effects of light-dark (LD) cycles shorter than 24 hours on alert state of marmosets. Methods: Six adult females, in individual cages, were maintained under the symmetric light-dark (LD) cycles T21, T21.5 and T22 during 60, 35 and 48 days, respectively, in a room with constant 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. The vocalizations (an alert indicator) of all the animals were continuously recorded by a microphone installed in the room, connected to a computer. Results: There were observed two circadian components for vocalizations frequency and duration in the three external LD cycles, being one synchronized to the LD cycle, named light-entrained component (LEC), and the other an average of endogenous period of all females, named non-light-entrained component (NLEC). The percentage of variance (VSP) of vocalizations frequency was 16.6%, 13.9%, 10.7% for LEC and 9.3%, 4.0%, 4.2% for NLEC; and of vocalizations duration was 15.9%, 12.4%, 11.4% for LEC and 9.8%, 4.6%, 4.3% for NLEC. The occurrence of vocalizations at the light phase was of 95.2%, 95.0%, 98.3% for frequency and 95%, 95.9%, 98.8% for duration. All the values were given for T21, T21.5 and T22, respectively. Conclusions: Expression of two circadian components in vocalizations rhythmicity of marmosets under T cycles shorter than 24 hours indicates that alert state is driven by at least two different groups of circadian oscillators, being one capable of entrain to the external LD cycle while the other can’t, depending on T cycle. Both components were more evident and similar in T21 than in T21.5 and in T22. Based on this data, we suggest that marmosets under T21 can be a good animal model to force internal desynchronization. This can be very helpful to provide new treatments to disturbs in circadian rhythmicity, including cognition deficit. 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