Seasonal variations in pineal 5-methoxytryptophol (5-ML) concentrations and in the daily pattern of pineal 5-ML and melatonin in the desert rodent Jaculus orientalis: effect of prolonged illumination during the night.
Seasonal variations in daytime pineal 5-methoxytryptophol (5-ML) and in the daily pattern of both pineal 5-ML and melatonin concentrations were measured by radioimmunoassay in male and female jerboas, Jaculus orientalis. Pineal 5-ML content was found to be low in winter and spring and showed a short but marked increase in summer. A clear daily rhythm was present in pineal 5-ML in September, with high concentrations during daytime and low concentrations during nighttime. In May there was a considerable drop in the daytime values and a marked decrease in the amplitude of the rhythm, while in December the daily rhythm completely disappeared. On the contrary, a clear daily rhythm was observed for pineal melatonin in September, December, and May with high values during nighttime and low values during daytime; no differences in the amplitude of the rhythm could be observed. Illumination during early night prevented both the nocturnal decrease of 5-ML and the increase of melatonin in September; in May illumination had no clear effect on 5-ML, while it prevented the normal increase of melatonin. These results suggest a possible desynchronization between the regulation of 5-ML and melatonin synthesis and release, and stress the complexity of the mechanisms involved in the environmental synchronization of seasonal functions.
Lakhdar-Ghazal
N
N
Unité de Neurosciences, Faculté des Sciences, Université Mohammed V, Rabat, Maroc.
Vivien-Roels
B
B
Pevet
P
P
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology; D005260:Female; D007211:Indoles / Q000378:metabolism*; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D017440:Photoperiod; D010870:Pineal Gland / Q000378:metabolism*; D011863:Radioimmunoassay; D012377:Rodentia / Q000378:metabolism*; D012621:Seasons
D007211:Indoles; C002465:methoxytryptophol; D008550:Melatonin