1,720,968 research outputs found
The pineal and circadian rhythms of temperature selection and locomotion in lizards
No full textThe existence of a circadian rhythm of behavioral temperature selection has been demonstrated in lizards (Podarcis sicula) held on a thermal gradient in constant darkness. This rhythm becomes temporarily abolished during 1 week following parietalectomy and 2-3 weeks following pinealectomy. Parietalectomy does not affect the locomotor rhythm, while pinealectomy invariably lengthens the freerunning period of this rhythm. These results support the contention of separate control systems for the temperature selection rhythm and the locomotor rhythm. As neither rhythm is definitively abolished by parietalectomy and pinealectomy, other pacemaking components exist elsewhere in the circadian system of Podarcis sicula which can control both rhythms
Investigations on the role of the pineal, the retinae, and melatonin in the circadian system of the lacertid<i>Podarcis sicula</i>
No full textCircadian organization in the ruin lizard Podarcis sicula: the role of the suprachiasmatic nuclei of the hypothalamus
No full textCircadian organization in the ruin lizard Podarcis sicula: the role of the suprachiasmatic nuclei of the hypothalamus
No full textThe effects of electrolytic lesions to the suprachiasmatic nuclei of the hypothalamus (SCN) on circadian rhythms of locomotor activity were examined in ruin lizards Podarcis sicula maintained in constant darkness and constant temperature (29°C). All lizards (N = 15) in which the lesion damaged 80% or more of the SCN became behaviorally arrhythmic. On the contrary, locomotor rhythms persisted in all cases (N = 11) when the SCN remained intact and lesions were confined to neighbouring regions of the preoptic area. Taken together with previous work which demonstrates that the pineal and the retinae are not essential for the persistence of circadian locomotor rhythmicity in Podarcis sicula and with recent evidence showing the homology between the SCN of lizards and those of mammals the present results strongly support the view that the SCN of Podarcis sicula contain the primary pacemaker(s) for locomotor rhythms
Seasonal variations of pineal involvement in the circadian organization of the ruin lizard Podarcis sicula
No full textTo establish whether the effects of pinealectomy on circadian locomotor rhythmicity vary with season, we examined, in constant temperature and darkness, the locomotor behaviour of ruin lizards Podarcis sicula collected and subjected to pinealectomy at different times of the year. Changes in the freerunning period in response to pinealectomy were found to be significantly greater in summer than in winter, spring and autumn. Circadian activity time changed significantly in response to pinealectomy only in spring and summer. Furthermore, while pinealectomy was effective in altering the locomotor rhythms of all individual lizards tested in summer, the same surgery was found to leave locomotor rhythmicity of many lizards tested in autumn and winter completely undisturbed. These results demonstrate for the first time in
a non-mammalian vertebrate that the pineal gland is centrally involved in determining circadian organization in some seasons and is only marginally involved in others
Extraretinal photoreceptors can mediate the response of the circadian system to changes in level of constant light in ruin lizards.
No full textControl mechanisms of the seasonal changes of activity pattern in ruin lizards: melatonin and the pineal are involved.
No full textThe pineal, the retinae and melatonin in the circadian system of the European ruin lizard.
No full textElectrolytic lesions to the optic chiasm affect circadian locomotor rhythms in lizards
No full textElectrolytic lesions to 85-95% of both optic nerves at the level of the optic chiasm (OC-X) induce a significant shortening of the freerunning period (tau) of locomotor rhythms in Podarcis sicula held in constant temperature (29°C) and constant darkness. Together with previous data in P.sicula, showing that also retinalectomy (RET-X) in constant darkness mostly induces a shortening of tau, the present results demonstrate that the retinae play a central role in the control of behavioural circadian rhythmicity independently of light perception. The fact that OC-X and RET-X affect locomotor rhythms in the same way (mostly by shortening tau) strongly supports the contention that the influence of the retinae on the circadian system is neurally mediated
New experiments on the role of the pineal gland in the control of circadian locomotor rhythms in lizards: effects of pineal transplant.
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