Photoperiod and ambient temperature as environmental cues for seasonal thermogenic adaptation in the Djungarian hamster, Phodopus sungorus.
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Adaptation, Physiological↗
Biomedical subjects
S Steinlechner
Publications and source records attributed to S Steinlechner.
In vivo responses of the pineal gland of the Syrian hamster to isoproterenol or norepinephrine.
The influence of isoproterenol, a norepinephrine (NE) agonist, or NE itself on pineal melatonin levels in adult male Syrian hamsters was examined in a series of studies. Isoproterenol (3 mg/kg) failed to stimulate pineal melatonin production in hamsters kept under light:dark cycles of 14:10 or in hamsters that had been superior cervical ganglionectomized for 1 week. When the drug was given to animals kept under continual light for 7 days it caused a low-grade rise in pineal melatonin, however, this was not confirmed in a second experiment. When the dosage of isoproterenol was increased to 10 mg/kg and 2 injections of the drug were given (at 2 h intervals) pineal melatonin levels also did not exhibit a significant increase. Finally, the administration of NE at a dosage of either 2.5 or 5 mg/kg also failed to augment melatonin levels in the hamster pineal gland.
Animals↗
Photoperiodic control and effects of melatonin on nonshivering thermogenesis and brown adipose tissue.
Exposure to a short photoperiod improved the thermogenic capacity, and cold resistance of Djungarian hamsters and increased the respiratory power of their brown adipose tissue. Exposure to a long photoperiod caused a decrease in thermogenic measurements. This thermotropic action of the short photoperiod was detectable only during late summer and fall. A similar thermotropic response could be elicited by implanting hamsters with melatonin, indicating that the pineal may be involved in photoperiodic control of thermoregulatory effectors.
Adipose Tissue, Brown↗