Oral melatonin produces arrhythmia in sparrows

Abstract

Above 24 h the values diminish slightly as a function of T. The critical number of short night signals depends on the light regime. The clock-counter system works better with very long cycles. Below 24 h it loses its efficiency. If there were a circadian element in the system (either for clock or for counter), a higher efficiency would be expected as one approaches the natural period of 24 h. The measure of time provided by the Zeitgeber is determined by a circadian system for the induction at the larval stage while it is apparently accomplished according to an hour-glass model for diapause termination in the pupa. This change in operation during development is indicated here for the first time. Metamorphosis in holometabolous insects involves the almost total restructuring of the tissues and organs, including the central nervous system. Two situations may occur: either there is a single clock to control entry into and exit from diapause, and metamorphosis provokes a change in its operation, or induction is controlled by a larval clock operating with a circadian oscillator and diapause termination by another, anatomically different pupal clock, working according to the hour-glass model.Summary. In two arctiid species, Holomelina lamae and H. aurantiaca, which rhythmically extrude and retract their abdominal tips during pheromone emission, pheromone glands contain up to three orders of magnitude more of the major component than in most Lepidoptera examined to date. Using an effluent collection technique, relatively high rates of pheromone emission were obtained from freely calling females. In contrast, volatilization rates from forcibly extruded glands were about 25 times lower for both species, suggesting that pulsation of the gland functions to increase the release rate.

Photoperiodism, pineal clock and seasonal reproduction in the Indian Weaver Bird (Ploceus philippinus)

“…Also, as noted above, a direct effect of the pinealectomy and/or melatonin administration has been shown in regulation of several circadian rhythms (Gaston and Menaker 1968;Gaston 1971;Binkley et al 1971Binkley et al , 1972Menaker and Zimmerman 1976;Turek et al 1976;Binkley and Mosher 1985;Gwinner et al 1987Gwinner et al , 1997Beldhuis et al 1988;Gwinner 1989;Oshima et al 1989;Chabot and Menaker 1992;Lu and Cassone 1993a, b;Pohl 2000). Of all the overt markers of the circadian system, the rhythm of locomotor activity is conveniently measurable and is also reliable.…”

Neural Basis of Avian Circadian Rhythms

“…In fact, melatonin implants in the House Sparrow shorten free-running activity rhythms in some animals and induce continuous activity in others (87). Melatonin administered in drinking water results in arrhythmic activity in House Sparrows (13).…”

Circadian organization and the role of the pineal in birds

“…Depending on dosage, melatonin causes either arrhythmicity or changes in the period of the free-running activity, feeding, or body temperature rhythms. Arrhythmicity has been observed in house sparrows, Java sparrows, house finches, pigeons, and Japanese quail and period changes have been observed in house sparrows, starlings, and Japanese quail (Beldhuis et al, 1988;Binkley and Mosher, 1985;Ebihara and Kawamura, 1981;Fuchs, 1983;Turek et al, 1976;Underwood and Edmonds, 1995). House sparrows implanted with silastic capsules containing melatonin show accelerated reentrainment to shifts in the phase of the LD cycle (Hau and Gwinner, 1995).…”