What can I learn from worms? June 2012Lesson 1: What is regeneration?

Model Organisms Used in Neuroscience Research

Sea slug (Aplysia caligornica)

The neurons of this West Coast invertebrate are unusually large—about 1 millimeter long at the most—and visible to the naked eye. The sea slug’s cells are easily manipulated and useful for understanding how we learn and how diseases like Alzheimer’s work at the cellular level. Furthermore, the sea slug has only

20,000 brain cells, compared to the 100 billion of a human brain. The neuroscientist Eric Kandel and his colleagues were awarded with a Nobel Prize in 2000 for work using sea slugs to study how memories are formed at the molecular level.

Zebrafish (Danio rerio)

Zebrafish are great for studying a variety of human diseases. Besides their easily observable and testable behaviors, these fish have a sleep cycle that is very similar to mammals. Zebrafish are easier to take care of than mice, and are used to study circadian rhythms and other research topics. For example, when scientists injected stem cells from zebrafish into the diseased retinas of rats, the stem cells developed characteristics of the rats’ neuronal cells. This is promising research for humans who suffer from damaged retinal neurons, which is related to glaucoma and diabetes-related blindness.

Fruit fly (Drosophila melanogaster)

You may think nothing about this 3-mm long, tiny insect you see around spoiled fruit or the trash, but this model organism has been used for over 100 years to study genetics. Fruit flies are convenient for this use because they have only four chromosomes, including sex chromosomes X and Y. However, these flies are so easy and cheap to breed, raise, and observe

that they have been used for many different types of studies including circadian rhythms, longevity, and alcohol tolerance. Thomas Hunt Morgan is a famous scientist who received a Nobel Prize in 1933 for his work using fruit flies to study the role of chromosomes in genetics.

Chimpanzees (Pan troglodytes)

This species is a member of the great ape family (Hominidae) along with gorillas, humans, and orangutans. Their closeness in relation to humans (we share 98% of our genome code) has made them useful for research in language development, tool use, surgery, and infectious diseases such as AIDS. Chimpanzees have even been launched into outer space by the United States space program NASA to study the effects of space travel on humans! In neuroscience, chimps are used to study complex brain processes such as face recognition and reasoning skills.

1

What can I learn from worms? June 2012Lesson 1: What is regeneration?

Guppy (Poecillia reticulata)

Guppies are used in genetic studies to observe mating and behavior patterns. The female guppy retains the embryos inside her body, observable to the naked eye, and gives live birth. It is known that females prefer complex and unique color patterns in their male mates, and that this preference contributes to color polymorphism, or multiple phenotypes, within the guppy species. Current research is focusing on social and environmental factors that affect a female’s selection of male mate and why females are generally more attracted to novel males, those they have not seen before.

Planaria (Schmidtea mediterranea)

Planarians are invertebrate flatworms with an amazing ability to regenerate. If you cut a piece of the planarian that is 1/279th of the body, an entire new flatworm can be generated! Because they are also easily observable creatures, researchers can manipulate planarians’ simple genome and observe changes in response to stimuli and how their nervous system controls learning, memory, and behavior. For these reasons, planarians can be used to understand the human genes associated with stem cell development and how these can be manipulated in neurogenesis and used to treat patients with neurodegenerative disorders.

Zebra finch (Taeniopygia Guttata)

Zebra finches are an intriguing model organism due to their ability to learn songs produced by members of their species. Researchers are able to study the underlying neural networks that allow the male finch to learn a song and other social behaviors. The male finch’s song is generally learned from his father but can have some variation due to his environment and other male birds. Research has shown that singing to females strongly activates the male finch’s reward centers of the brain, which makes them happy. These same reward centers are strongly activated in humans addicted to drugs. Thus, the finch provides a model to study these reward centers, and whether damage caused by an addiction to drugs can be remedied.

2

Animal Testing

Non-human animals have helped scientists and doctors cure many diseases and save millions of human lives by developing vaccines, surgery and organ transplant techniques, and antibiotics. Today, there are strict federal policies regarding the treatment of animals in research in the United States. Any scientist that receives federal funding must justify research involving animals and show that animals will not be “unnecessarily burdened.” This means that the number of animals used in research is minimized, experiments are refined to reduce pain and distress, and computer or in vitro (intact or natural state) models are preferred in experiments.