Cold prevents the light induced inactivation of pineal N-acetyltransferase in the Djungarian hamster, Phodopus sungorus

Abstract

In the Djungarian hamster seasonal acclimatization is primarily controlled by photoperiod, but exposure to low ambient temperature amplifies the intensity and duration of short day-induced winter adaptations. The aim of this study was to test, whether the pineal gland is involved in integrating both environmental cues. Exposure of hamsters to cold (0 degrees C) reduces the sensitivity of the pineal gland to light at night and prevents inactivation of N-acetyltransferase (NAT). The parallel time course of NAT activity and plasma norepinephrine content suggests that circulating catecholamines may stimulate melatonin synthesis under cold load.

Significance and application of melatonin in the regulation of brown adipose tissue metabolism: relation to human obesity

“…Likewise, in some mammals cold exposure increases the activity of pineal gland to produce additional melatonin; this is reported for the Syrian hamster (122) and the spontaneously hypertensive rat and the Wistar/Kyoto rat (123). Cold exposure also reportedly neutralizes the suppressive effect of light exposure on melatonin synthesis in the pineal gland of Djungarian hamsters (124). This finding was somewhat unexpected as light exposure at night is considered the most potent factor to suppress melatonin production.…”

Annual rhythms that underlie phenology: biological time-keeping meets environmental change

“…Under natural photoperiod, this may translate to a one-week delay of testicular regression when temperature is 48 higher. Temperature effects in small mammals are thought to be mediated through melatonin [63,66,69], and would thereby take place through modulation of the essential input signal to the annual hypothalamic timing mechanism. Based on neuroanatomical evidence in the prairie vole, Kriegsfeld et al [64] suggest that lower temperatures may inhibit the release of GnRH by neurons located in a brain area that also contains temperature-sensitive neurons.…”

Generation of the Melatonin Endocrine Message in Mammals: A Review of the Complex Regulation of Melatonin Synthesis by Norepinephrine, Peptides, and Other Pineal Transmitters

“…SIMONNEAUX AND RIBELAYGA modulates the inhibitory effect of light applied at night (Stieglitz et al, 1991). Currently, anatomical structures and transmitters involved in these effects of temperature are not known and could act directly on the pineal gland or on intermediate structures sensitive to the temperature.…”