Circadian Rhythm and Synapse Activity in Zebrafish


The other day I found an article that seemed all too perfect. Development. Neurology. Zebrafish. For those of you who don’t know, these little fishies are not only PZ’s specialty but are also currently taking over our lab (You will be missed, fishies in tank #3).

In zebrafish, the sleep-wake cycle is regulated by hypocretin neurons (HCRT). These neurons also play a major role in mammals as well and if damaged can lead to narcolepsy. The researchers labeled these neurons in zebrafish with a presynaptic marker synaptophysin (SYP) attached to a fluorescent dye. Now the researchers can look at activity across the span of a day to visually quantify changes in baseline function or artificially produced by various conditions (e.g. sleep deprivation). So,  they irritated fish for several hours after normal sleeping time until the fish were nice and sleep deprived.

The sleep deprived fish showed homeostatic influences on the number of HCRT synapses. Why is this important? The fish showed that upon sleep deprivation more synapse terminals were created  to maintain cellular balance. Yet, simultaneously, the natural circadian rhythm began to decrease the number of synapses from the point of initial sleep deprivation. Homeostatic effects are estimated to be a mere 17% and this result appears only after six hours of deprivation. Essentially, as the day wears on the brain winds up more and more. The circadian rhythm counteracts this by gradually resetting the system back to baseline. A portion of this study showed that as the system tries to reset, sleep deprivation will weakly offset efficacy leading to impairment in memory retainment (and overall cranky fish).

*Professor, I would have gotten that question right but the course workload created homeostatic effects which led to faulty memory retainment!*

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About James R

A twice-over senior at the University of Minnesota - Morris. View all posts by James R

4 responses to “Circadian Rhythm and Synapse Activity in Zebrafish

  • Joan

    Here is this post’s extra curricular, non-course related question by your non-biologist reader (if you are up for it):

    I can’t get at the article, and I am dying to know…

    What does faulty memory retainment in zebra fish kept in tanks (without predator fish, I’m guessing?) translate into behavior wise? What do they stand to forget due to these homeostatic effects?

    • James R

      Good catch! I actually had the wrong link posted. It’s fixed if you’re still interested in the original. As for the behavior, I haven’t the slightest idea. The zebrafish are a relatively new organism of study for myself and I’m not yet well versed enough to have competence on them. But, this research provides a good starting point for observing potential correlations in easier research subjects, such as humans.

  • Joan

    Thank you! (Joan waves as she skips off to read about Circadian and Homeostatic Regulation of Structural Synaptic Plasticity in Hypocretin Neurons….)

  • Kat Bjornstad

    The way you ended this post is amazing, and I am writing that down for future use. Sadly it may not be as funny with my professors, as I am a history major and there’s no guarantee my teachers will have a clue what that means.

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