Involvement of orexin A in nocturnal melatonin secretion into the cerebrospinal fluid and the blood plasma in seasonal sheep
Katarzyna Kirsz , Małgorzata Szczęsna , Weronika Biernat , Edyta Molik , Dorota Zięba-Przybylska
AbstractIn sheep, differences in orexin A (OXA) gene expression and activity are related to changes in energy demandand seasonal reproduction. However, the mechanism by which and the key place where the OXA signal isintegrated with photoperiod, whose main biochemical expression is melatonin (MEL), remain unknown. Weexamined the effects of cisterna magna injections of OXA (0.3μg/kg body weight) on nocturnal cerebrospinalfluid (CSF) and plasma MEL concentrations; mRNA and protein expression of two rate-limiting enzymes for MELbiosynthesis, tryptophan 5-hydroxylase-1 (TPH1) and arylalkylamine-N-acetyltransferase (AA-NAT); and OXAreceptor (OX1R, OX2R) expression in the pineal gland (PG) obtained from twenty ewes during the short-day (SD)and long-day (LD) seasons. OXA increased (P < 0.001) CSF and plasma MEL concentrations regardless of theseason. Plasma MEL was positively correlated (P < 0.001) with CSF MEL in the OXA-treated sheep in bothseasons. OXA had no effect (P > 0.05) on TPH1 transcript or protein level but upregulated (P < 0.05) AA-NATmRNA and protein expression in both seasons. OXA enhanced (P < 0.05) OX1R mRNA level only during the LDseason. Our results show that the endocrine activity of the ovine PG is regulated by day length and non-photicsignals via hypothalamic OXA. These results are important for understanding the work of the biological clockand recognizing mechanisms responsible for the adaptation of seasonal animals to the changing external en-vironment conditions. OXA and MEL are both involved in the regulation of the sleep-wakefulness system,therefore our results can be used in the study on the circadian rhythm disorders in humans (e.g. jet lag, insomnia,seasonal depression).
|Journal series||General and Comparative Endocrinology, ISSN 0016-6480, e-ISSN 1095-6840, (N/A 100 pkt)|
|Publication size in sheets||0.5|
|Keywords in English||orexin A, Orexin receptors, Melatonin, Tryptophan 5-hydroxylase-1, Arylalkylamine-N-acetyltransferase, Sheep|
|Publication indicators||= 0; : 2018 = 1.006; : 2018 = 2.445 (2) - 2018=2.66 (5)|
|Finansowanie||This work was supported by a grant from the National Science Center in Poland (grant number NCN 2017/01/X/NZ9/00204).|
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