| Many biochemical, physiological, and behavioral parameters exhibited by organisms show daily fluctuations, and most of these fluctuations persist when the organisms are maintained in constant environmental conditions, thus demonstrating that they are driven by an endogenous oscillator. Rhythms that persist in constant conditions with a period close to 24-h are called circadian. In reptiles and other nonmammalian vertebrates the importance usually ascribed to the pineal gland and the eyes in the circadian organization and sustainment. But during the last decade the suprachiasmatic nucleus(SCN) have also been recognized to play a role in the circadian system of lizards and the SCN of lizards are topographically similar to the SCN of rodents. Furthermore, the fact that some circadian rhythm of behavior is not definitely abolished after both parietalectomy and pinealectomy suggested that the SCN or neighboring hypothalamic areas may also be involved in driving this rhythm. Arginine vasopressin belonging to Neurohypophyseal hormones which occurs within the various classes of vertebrates and nonvertebrates, is an ancient hormone of animal. AVP, that is expressed with a circadian rhythm in DD is considered as an important candidate for output signal and modulator of the SCN of mammalians. Arginine-vasotocin(AVT) is known to be the homologous form of AVP in reptiles, then what is the role of AVT in reptilian circadian rhythms?The present investigation was carried out in our model animal Gekko swinhonis, and was aimed at testing whether AVT be used as marker(s) of circadian oscillation of the lizard . For this purpose, by using immunohistochemistry and morphometry we examined the distribution of AVT in the brain and the circadian changes of AVT expression in the hypothalamus of... |
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