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| Titel: |
Daily Rhythm of the Response to Noradrenaline in Djungarian Hamsters Acclimated to Cold and Short Photoperiod |
| Auteur: |
Jefimow, M. Masuda, A. Oishi, T. |
| Verschenen in: |
Biological rhythm research |
| Paginering: | Jaargang 31 (2000) nr. 5 pagina's 545-558 |
| Jaar: |
2000-12 |
| Inhoud: |
We investigated the daily rhythm of the response to noradrenaline injections in Djungarian hamsters (Phodopus sungorus sungorus) at neutral ambient temperature, under long photoperiod (L:D 12:12) and after four weeks of acclimation to cold (10ºC) and short photoperiod (L:D 8:16). Animals were injected with noradrenaline (0.6 mg/kg) every four hours. Body temperature and gross motor activity were measured with MiniMitter transmitters implanted into abdominal cavity. Additionally, we measured body weight and food intake prior to, and after acclimation. After four weeks of acclimation, the experiment was performed under LD cycle and then repeated during one-day of constant light (LL) and constant darkness (DD). In animals acclimated to L:D 12:12 and ambient temperature of 25ºC, noradrenaline injections caused short-lasting increase in body temperature followed by marked decrease. There was no significant difference in the magnitude of the reaction between light and dark phase of the day. After acclimation to cold and L:D 8:16, under LD conditions, we recorded significant differences between the responses to the noradrenaline injections during light and dark phase of the day. Post-injection increase was higher during the day than during the night while following noradrenaline-induced hypothermia was much more pronounced in darkness. In experiments performed after acclimation to cold and short photoperiod but during one day of LL and DD regimes, these differences were attenuated. Data presented here indicate that in cold acclimated hamsters, the response to exogenous noradrenaline depends on the time of injection and it exhibits clear daily rhythm. The rhythmicity is altered under LL and DD regimes. It seems that post-injection increase in body temperature elicits following hypothermia. This hypothermia might be of a great ecological importance. Reasonable lowering of body temperature would be a protective mechanism, allowing for energy charge restoration. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 2 van 7 gevonden artikelen
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