Pineal rhythms are synchronized to light–dark cycles in congenitally anophthalmic mutant rats

Centre for Cellular and Molecular Biology, Hyderabad, 500 007, India
Brain Research (Impact Factor: 2.84). 05/1999; 825(1-2):95-103. DOI: 10.1016/S0006-8993(99)01226-3
Source: PubMed


Genetically mutant anophthalmic rats lacking a complete visual system due to the absence of eyeballs and optic nerves up to the optic chiasma were used as a model to study photo-regulated physiological activities. The photoreception in these mutant rats was determined by measuring the neuroendocrine response of the pineal gland-melatonin levels in the serum, and synaptic ribbon complexes (SRCs) in the pinealocytes. These parameters were studied in both normal and anophthalmic rats maintained under light–dark (LD 12:12), continuous dark (DD) and light (LL) conditions. Both normal and mutant anophthalmic animals showed nocturnal increases in serum melatonin levels and in the number and diameter of SRC and their vesicles in the pinealocytes in LD. The daily rhythms persisted even upon transfer to DD both in normal and mutant rats, whereas in LL, the nocturnal elevation of both the parameters disappeared. These observations suggested that congenitally blind rats can perceive light. The studies of these parameters in both normal and mutant rats in reversed-LD conditions confirmed that pineal rhythms can be entrained by light–dark cycles in congenitally anophthalmic mutant rats through a nonvisual system for light perception.

Download full-text


Available from: James Olcese
  • Source
    • "Blue light is being identified as a new environmental pollutant. Earlier we studied the effects of day light in anopthalmic rats and concluded that the mammalian eye sub serves at least two photic systems: the occipital cortex, which mediates the conscious perception of light and recognition of images and a subcortical system that med-iates light-sensitive synchronization of the circadian pace-maker (Foster et al., 1991; Chaurasia and Gupta, 1999; Jagota et al., 1999). "
    [Show abstract] [Hide abstract]
    ABSTRACT: A correlation between prevalence of breast cancer with blindness has not been attempted in India and only scanty information is available at the world scenario as well. We have done a pilot study by epidemiological survey of blind menopausal (high risk age group) women (n = 204) from Chennai to find the prevalence of the disease. In the present study, menopausal visually challenged women have shown that the ratio at risk of developing breast cancer in this group is very much lower (1:100) compared to sighted women in the similar age group, The risk of developing breast cancer is 1:78 (Cumulative Risk 35 -64 age), among sighted women in Chennai. Statistical analysis of the present data also provide enough evidence that blind women who are > 40 years of age had 13% greater risk of breast cancer compared with those in the study group < 40 years (RR = 1.125; 95% CI = 0.07 to 17.74).The susceptibility to develop the disease among partially blind women is almost twice than that of totally blind women (RR = 2.14; 95% CI = 0.14 to 33.68). Similarly menopausal stage of a woman has more risk of developing breast cancer than pre-menopausal stage (RR = 5.18; 95% CI = 0.33 to 80.75). Vision loss after menarche also indicates an increased risk (RR = 8.27; 95% CI = 0.54 to 127.6).The intervals for these risks give a very wide range of possible values for the corresponding risk ratio due to small sample size and the rarity of breast cancer among blind women. The topographical location of India close to the equator and life style pattern of the people could be the major reasons for the very low prevalence of breast cancer in Chennai. None of the other high or low risk factors were found to be influencing blind women to develop breast cancer. The relationship between visible light and breast cancer can be studied by taking blind menopausal women as a model.
    Full-text · Article · Nov 2009
  • Source
    • "For example, light-exposure of the popliteal region did not suppress plasma melatonin in humans [Lockley et al., 1998; Hebert et al., 1999], and no phase-shifting effects of light on the rhythms of melatonin, cortisol and thyrotropin were observed when the human abdomen and chest was light-exposed [Lindblom et al., 2000]. With one exception [Jagota et al., 1999], rodent data demonstrated that the eyes are necessary for circadian and visual photoreception. Most researchers of the circadian field therefore supposeÐas pointed out by [Yamazaki et al., 1999]Ðthat ªhumans can be phase-shifted by some uncontrolled aspects of the paradigm used by Campbell and Murphyº. "

    Full-text · Chapter · Dec 2004
  • Source
    • "The existence of a diurnal rhythm of melatonin secretion in a subterranean animal is not unprecedented, as ocular regression that is associated with adaptation to a subterranean habitat is not necessarily accompanied by a loss of circadian melatonin secretion. In fact, diurnal melatonin rhythms have been described previously in blind (Pevet et al., 1984; Green & Romero, 1997) and anopthalmic (Bartness & Goldman, 1989; Jagota et al., 1999) animals. In addition to being diurnal, melatonin secretion in C. damarensis seems to be circadian, as evidenced by the similar pattern of diurnal melatonin secretion in mole-rats transferred from a neutral photoperiod to continuous darkness in experiment 1. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Subterranean mammals inhabit an environment that is normally devoid of light and are therefore deprived of photoperiodic information that can be used to time important life-history events. An assessment was made of whether melatonin secretion in a strictly subterranean rodent, the Damaraland mole-rat Cryptomys damarensis, can be modified by photoperiod. In experiment 1, a clear diurnal rhythm of melatonin secretion in animals housed under a neutral photoperiod (12L:12D) was observed, with significantly higher melatonin concentrations in the dark compared to the light phase. The same diurnal melatonin rhythm was found 1 day after animals were transferred to either continuous light or continuous dark, suggesting that a circadian rhythm was maintained under acute exposure to light and dark. In experiment 2, melatonin secretion was monitored in a long (14L:10D) and short day (10L:14D) photoperiod and was found to be modified by the photoperiodic change. We therefore suggest that the Damaraland mole-rat possesses a circadian melatonin rhythm that can be physiologically modulated in response to photoperiod.
    Full-text · Article · Oct 2003 · Journal of Zoology
Show more