Daily variation of D2 dopamine receptor transcription in the brain of the Japanese eel Anguilla japonica and its regulation with dopamine and melatonin

Effects of dopamine and melatonin treatment on the expression of the genes associated with artificially induced sexual maturation in Japanese eel, Anguilla japonica

“…Jeng et al (2014) supported this suggestion; they reported that d2b mRNA abundance decreased in the forebrain and pituitary gland of Japanese eels during silvering. However, the effects of DA and DA + domperidone on d2b transcription levels were inconsistent with those observed in immature individuals (Byun et al, 2020). This phenomenon is attributed to negative feedback, as the functionality of D2B seems to be primarily prominent in sexually immature individuals, contributing to fundamental disparities in the levels of D2B between sexual immature and mature individuals.…”

“…The interaction between melatonin and DA in regulating the dopaminergic system has been explored in Japanese and European eels. Byun et al (2020) reported that the daily circadian variation in D2B receptor transcription was influenced by melatonin, and that melatonin treatment reduced d2b mRNA levels in the midbrain of sexually immature Japanese eels. This study suggested that melatonin in immature Japanese eels could have a positive effect on reproduction by controlling the dopaminergic inhibition of sexual maturation.…”

“…Fish (six individuals per stage) were collected from the tanks at weeks 0 (W0), 2 (W2), 4 (W4), 6 (W6), and 8 (W8) after hCG injection and then anesthetized with 0.01% 2-phenoxyethanol (Kanto Kagaku, Tokyo, Japan). Following decapitation, the whole brain and pituitary were removed from the skull, and the whole brain was separated into the forebrain, midbrain, and hindbrain (Byun et al, 2020). Testes were collected from the body cavity and weighed.…”

“…Pharmacological studies have revealed that D2B receptors may be involved in sexual maturation in the European eel, because a D2 receptor antagonist stimulates LH expression in vitro (Jolly et al, 2016). Byun et al (2020) reported that day‐low and night‐high fluctuations in melatonin play a key role in the rhythmic changes in the messenger RNA (mRNA) abundance of the d2b receptor in the midbrain of the Japanese eel.…”

What Goes Wrong during Early Development of Artificially Reproduced European Eel Anguilla anguilla? Clues from the Larval Transcriptome and Gene Expression Patterns

“…Like d2br, melatonin regulates motor behavior in zebrafish larvae [102][103][104]. Melatonin possibly even influences the d2br transcript levels since high day/low night variation of d2br have been observed in adult eels [120]. The daily variations of the dopaminergic and melatonergic systems in eel larvae were beyond the scope of our study, but should be further investigated.…”