Hungarian Brain Research Program(2017-1.2.1-NKP-2017-00002)
The aim of this study is to obtain a more complete picture of blood plasma melatonin
concentrations in the donkey mares. To this purpose, sampling and statistical processing
were carried out in such a way that allowed the researchers to establish the annual
and daily rhythms. Based on human observations, according to the hypothesis of the
authors, the blood plasma melatonin concentration of pregnant individuals rises during
the late gestational period, before parturition. To confirm this, the melatonin concentrations
of pregnant and non-pregnant jennies were monitored and compared. In regard to the
circannual rhythm, the significantly lowest midnight melatonin value (27.67 pg mL–1)
was typical for the summer solstice. Under consideration of circadian changes, a significantly
strongest melatonin production (45.16 pg mL–1) was observed on the night of the winter
solstice (p < 0.001). Considering gestational age, the blood plasma melatonin concentration
(around 38 pg mL–1) does not change as gestation progresses (p = 0.136). The results
obtained in this studied population of the domestic ass usefully expand the little
knowledge previously gathered about the development of the blood plasma melatonin
concentrations of this species.