The relationship between tryptophan pyrrolase activity, 5-HT metabolism in the brain and induction of hibernation
Novotná, R.; Civín, J.
Physiologia Bohemoslovaca 28(4): 339-346
1979
ISSN/ISBN: 0369-9463 PMID: 158774 Document Number: 148898
Data on the mechanism controlling 5-HT [5-hydroxytryptamine] turnover in the CNS during hibernation were obtained by studying the precursor supply furnished by liver tryptophan pyrrolase (LTP). LTP activity was measured at +37.degree. C during all 4 seasons in golden hamsters [Mesocricetus auratus] living and hibernating under outdoor conditions. Data for hibernating and for the control, non-hibernating hamsters adapted to constant laboratory conditions were compared. LTP activity diminished with the onset of the prehibernation period. The maximum decrease in LTP activity (about 50%) occurred during hibernation. Immediately after arousal from hibernation, activity rose by 100% compared with the summer values. The minimum LTP activity measured at temperatures of below +37.degree. C in hibernating hamsters indicated the temperature optimum for LTP did not change during hibernation. No seasonal changes in LTP activity were observed in control hamsters living under constant laboratory conditions. The decrease in peripheral tryptophan metabolism is related to hibernation only. Apparently the possible increase in the blood tryptophan level owing to diminished LTP activity is needed for enhanced 5-HT turnover during hibernation. Since liver LTP is activated by corticosteroids, the decrease in its activity indicates that corticosteroid and ACTH production are very low during hibernation. Apparently seasonal changes in the activity of the pituitary-adrenal axis and 5-HT pathways in the CNS are necessary for the induction of hibernation.