Analysis of the Mechanism underlying the Rhythm Reversal from Diurnal to Nocturnal in the Cricket Gryllus bimaculatus, with Special Reference to the Role of Serotonin : Physiology

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The cricket, Gryllus boimaculatus, shows a rhythm reversal from diurnal to nocturnal in about a week after the imaginal molt. In the present study, we investigated the role of serotonin (5-HT) in the rhythm reversal. The 5-HT content in the brain measured by HPLC equipped with an electrochemical detector gradually increased after the imaginal molt, and in fully nocturnal adults it was about 2 times of nymphal level. We then examined thee ffects of 5,7-dihydroxtryptamine (5,7-DHT), a selective neurotoxine to serotonergic neurons, on the locomotor rhythm. In most animals with 5,7-DHT (25 μM or 250μM, 32.2 nl) injected into the brain, daytime activity significantly increased even after the rhythm reversal, while nighttime activity was not significantly affected, forming rather diurnal pattern. The serotonin content in the brain of animals injected with 250μM 5,7-DHT was reduced by about 30%. On the basis of these results, possible involvement of 5-HT in the neural mechanism controlling the locomotor rhuthm is discussed.
社団法人日本動物学会の論文
2000-11-01