The humble laboratory mouse, which has suffered all manner of indignity in the name of science, has now really got something to worry about. Scientists have worked out how to make a mouse neurotic and have produced a Woody Allen of the murine world - a mouse that is born anxious.
A single gene has been discovered to play a formative role in whether mice are bold and inquisitive or huddle in a corner in a paroxysm of nervous indecision. Worry, it seems, is as much a part of the genes at is its upbringing. Although some laboratory mice can be made to achieve a state of neurosis, some are born to it.
Scientists at the Salk Institute in La Jolla, California, found that removing a gene that allows an anti-stress hormone to work in the brain causes a mouse to become anxious.
The resulting neurotic mice approach new situations tentatively and appear to suffer stress more readily than normal mice.
For example, ordinary mice can be restrained for 10 minutes with little effect, but the scientists report the neurotic mice becoming stressed within two minutes of enforced restraint.
The altered mice also produce seven times more of the major stress hormone - corticosterone - than normal mice.
The researchers, writing in the journal Nature Genetics, said the neurotic mice would be useful in the study of errors in chemical pathways of the human brain that can lead to serious neuroses in psychiatric patients, and would help develop new drugs.
The neurotic mice will be studied alongside another mouse developed at the same laboratory. A genetic mutation in this mouse has resulted in it being relaxed and laid back, which has earned it the nickname "mellow mouse" - a true native of California.