Scientists are curing a form of diabetes in rats, a type that also affects humans, by transplanting brain tissue from normal rat fetuses.

The research is part of a growing thrust at several centers, a thrust that could point the way to correcting or ameliorating many human brain disorders, including strokes, Parkinson's disease and damage caused by brain tumors or accidents.

The latest research was done by Drs. Don Gash and John and Celia Sladek at the University of Rochester.

The development of the ability to transplant brain cells to correct central nervous system deficiencies "has extraordinary theoretical and clinical implications," the Rochester scientists say in this week's issue of Science magazine.

In practical terms, treating human brain and nerve problems by transplanting fetal tissue would mean using bits of brain from infants that were either purposely or spontaneously aborted.

This might raise huge legal, moral and emotional problems today. But any human applications are probably 10 years away, various scientists guessed yesterday, and one said: "I think if this technique becomes possible, the demands of the sick would outweigh any objections to using a little fetal tissue for humanitarian purposes. It might even become immoral not to use it."

Also, said Dr. Raymond Lund of the Medical University of South Carolina, "It is quite possible the human brain might accept tissue of a sufficiently close animal type," such as brain tissue from a primate fetus. Lund bases this conjecture (his term) on some success he has had in transplanting embryonic chick nervous system tissue into rats' brains.

For the most part, Lund has grafted tissue from the visual systems of fetal rats' brains into adult rats.

"The main thing I'm interested in," he said, "is whether you can transplant tissue into a host brain and have it develop and make the appropriate connections. This now seems possible."

Last year a National Institute of Mental Health research team -- working with scientists in Colorado and Sweden -- reported creating a condition much like human Parkinson's disease in rats, then making them better by grafting brain tissue from rat fetuses.

The University of Rochester scientists worked with a strain of rats habitually afflicted with diabetes insipidus. In this disease -- uncommon but seen in some persons, especially after traumatic auto accidents -- the brain fails to make an essential water-conserving hormone called vasopressin.

As a result, affected individuals drink and excrete copious amounts of water. Humans can control the disease by using a vasopressin nose spray.

The Rochester group has improved the condition of 14 rats by fetal brain transplants, achieving success in 20 per cent of their tries.