Kassel biologist researches the inner clock

Biological clocks control many vital processes in humans and animals. For example, they determine eating and sleeping rhythms. Many small clocks are distributed throughout the body, for example in the brain, the eye, the liver or the kidney. Here, certain chemical processes run in very regular cycles. If these clocks get out of sync, humans and animals become tired, less efficient or even ill. Using the Madeira cockroach and the tobacco hawkmoth as examples, biologists at the University of Kassel are investigating how the networking and interaction of the many internal clocks in the insect is controlled by neuropeptides. Prof. Dr. Monika Stengl, head of the Department of Animal Physiology / Neuroethology at the University of Kassel, explains: "Whether cockroach or human - at the molecular level, the processes that take place in the so-called internal clocks in a 24-hour cycle hardly differ. Of course, there are small differences - but the general logic is the same."

Prof. Stengl has already researched part of the mechanism of internal clocks in Madeira cockroaches. She explains, "A central internal clock is located in the cockroach's brain and consists of individual neurons that communicate with each other via neuropeptides. This communication controls rhythms in the behavior and physiology of the animals - for example, the cockroach always sleeps during the day and becomes active at the beginning of the night. These behavioral rhythms, in turn, are influenced by external rhythms called timers. Such an external zeitgeber is, for example, the 24-hour rhythm of day and night." Prof. Stengl continued, "The many internal clocks couple with each other and are synchronized with the environment by the alternation of day and night. So light pulses find their way into internal clocks and speed them up, or slow them down, depending on the time of day." Thus, the 24-hour rhythm of humans also synchronizes with the external 24-hour rhythm of day and night. According to Stengl, the input of light into the mechanism of the internal clock creates a clock protein that in turn inhibits its own production. The rhythm in which this process takes place lasts about 24 hours. According to Prof. Stengl, the internal clocks can be read from the level of clock proteins in the pacemaker cells, or from electrical rhythms of their cell membrane.

As early as 13 years ago, the biologist was able to identify the pacemaker neurons that form a central internal clock in the Madeira cockroach's brain - these clock neurons contain the neuropeptide PDF (pigment-dispersing factor), which synchronizes other biological clocks. Prof. Stengl explains, "If you destroy this peptide in the cockroach's body, it becomes a-rhythmic - which means, for example, that it no longer sleeps and eats regularly." In humans, too, there is a peptide in the brain that corresponds to the PDF. As the most important coupling signal, it contributes, among other things, to the development of a sense of time (e.g. "today - yesterday - tomorrow").

Currently, the Kassel researchers are trying to identify other substances such as neuropeptides and neurotransmitters that are also part of the inner clockwork. They want to understand the network of clock neurons, how exactly the central clock in the cockroach's brain is linked to many other internal clocks in the cockroach's body. The research team is also interested in the effect of individual neuropeptides on the rhythmic feeding behavior of cockroaches. In addition, the biologists want to explore the connection between the electrical rhythms in the cell membrane of the pacemaker neurons and the rhythms in their gene regulation in the cockroaches. According to Prof. Stengl, the results of the basic research could later be applied in medicine, for example, as a basis for research teams looking at the influence of body functions that are not synchronized in time on the human psyche.

The effects of jetlag and time changes in humans can also be better explained in the long term through such basic research.

Tip from the biologist for jetlags

Knowing how internal clocks tick also helps explain a well-known phenomenon: It is much easier to delay the internal clock than to speed it up. If you want to adjust your body to winter time or fly west, you should expose yourself to a lot of light at the beginning of the night and also immediately adapt to the new sleeping and eating regime. When flying east or adjusting to daylight saving time, we have a much harder time. Prof. Stengl reports, "You have to give light late at night over several days to speed up internal clocks."
 

A photo of a Madeira cockroach (Photo: Achim Werckenthin, University of Kassel) at: http://www.uni-kassel.de/uni/fileadmin/datas/uni/presse/Rhyparobia_maderae_male_Foto_Achim_Werckenthin.png
 

A photo of Prof. Dr. Monika Stengl (Photo: Sonja Rode) at: https://www.uni-kassel.de/uni/fileadmin/datas/uni/presse/Prof._Dr._Stengl__Monika.jpg
 

Contact:

Prof. Dr. Monika Stengl
University of Kassel
Professorship of Animal Physiology
Tel.: +49 561 804 4564
E-mail: stengl[at]uni-kassel[dot]de