Effect of LED light spectra on exogenous prolactin-regulated circadian rhythm in goldfish, Carassius auratus

Abstract

We investigated the effect of light spectra on circadian rhythm by exogenous prolactin (PRL) using light-emitting diodes (LEDs): red, green and purple. We injected PRL into live fish or treated cultured brain cells with PRL. We measured changes in the expressions of period 2 (Per2), cryptochrome 1 (Cry1), melatonin receptor 1 (MT1) mRNAs, and MT1 proteins, and in the plasma PRL, serotonin and melatonin levels. After PRL injection and exposure to green light, MT1 expression and plasma melatonin levels were significantly lower, but the expressions of Per2 and Cry1 were significantly higher than the others. Plasma serotonin after PRL injection and exposure to red light was significantly lower than others. These results indicate that injection of high concentration PRL inhibits melatonin, and inhibited melatonin regulates circadian rhythm via clock genes and serotonin. Thus, exogenous PRL regulates the circadian rhythm and light spectra influence the effect of PRL in goldfish.

Keywords:

• circadian rhythm
• cryptochrome 1
• period 2
• prolactin
• melatonin receptor 1
• serotonin

Additional information

Funding

Funding. This work was supported by the National Research Foundation of Korea grant funded by the Korea government [grant number 2014R1A2A2A01002747] and by Korea Institute of Ocean Science and Technology (PE99234).