Scientists at the National Institute of Mental Health, in their ongoing efforts to unlock the secrets of incapacitating mood disorders, are recruiting volunteers for three studies.

In one, a chemical that scientists have used to induce dreams in sleeping subjects may help point the way to identifying people at risk for so-called "medical" depression and manic-depression, and may help show if vulnerabilities to such disorders are inherited.

The second study will examine and compare child-rearing practices of family groups in which the mother is even mildly depressed with those in which the mothers suffer no mood disorders.

The third study is a continuation and possible expansion of research demonstrating that many people, often intelligent and creative women, have mood swings dependent on seasons and, more specifically, on the length of the day. The studies have shown that such depression can be dispelled by daily periods of bright light.

Scientists at NIMH have been working on the causes and predictors of the so-called affective disorders--disabling and hard-to-treat illnesses of mood--with an eye to both better treatment and eventual prevention.

These illnesses are described as unipolar depression (deep apathetic hopelessness as the single symptom), bi-polar depression (so-called manic-depressive illness in which moods can swing from suicidal lows to agitated highs) and schizo-affective disorders, in which mood disorders may be accompanied by psychoses, often occurring between the mood cycles.

Research has identified a number of common characteristics, both behavioral and biochemical. Many of the victims suffer sleep disorders, for example, either sleeping too little or too much.

Studies in the NIMH sleep laboratory have demonstrated that patients suffering mood disorders go into the dream stage of sleep--REM or rapid eye movement sleep--much sooner than do normal subjects.

The researchers discovered that by intravenously administering varying quantities of arecoline, a chemical extracted from the betel nut, they could catapult any sleeping subject into a dream stage. But patients suffering from--in this study--manic-depressive mood disorders were much more sensitive to arecoline than normal subjects. This was true even though the patients were in a state of remission--showing no abnormal mood symptoms--when the tests were conducted.

The chemically induced dreams (in either patients or normal subjects) were no different in intensity or subject matter from natural dreams, the researchers found. However, it took much smaller amounts of arecoline to put the manic-depressive patients into the dream stage of REM sleep.

Arecoline is a stimulant and in some cultures is popularly extracted by chewing betel nuts--as in "Bloody Mary's chewing betel nuts; she is always chewing betel nuts," from the musical "South Pacific." Arecoline is also very similar in action to one of the brain's natural chemical messengers, the neurotransmitter acetylcholine.

Scientists have linked that neurotransmitter and the so-called cholinergic system--nerve fibers affected by acetylcholine--to mood disorders. Over-production of acetylcholine or of the chemicals or drugs that produce or release it, has a depressing effect. (There is even some evidence suggesting that some agricultural workers exposed to certain long-acting insecticides known to inhibit the breakdown of acetylcholine show symptoms of depression.) Chemicals that block acetylcholine can produce euphoria.

At the same time, says Dr. John I. Nurnberger Jr., a staff psychiatrist and clinic administrator at NIMH, some new studies have indicated that mood disorders may run in the family. A recent study of NIMH patients and several thousand brothers, sisters and adult offspring--"first-degree relatives"--confirmed, says Nurnberger, "that this is a familial disorder."

Not only is there a greater incidence of these mood disorders in relatives of people who have them, but the illnesses appear to be strongly related to each other--any of the illnesses can show up in relatives of a person with a single one. Also, says Nurnberger, "there seems to be a spectrum or continuum of illness in terms of risk," with relatives of people with schizo-affective disorders being most likely (nearly one in three) to get one of the disorders sooner or later. One in four children of manic-depressive (bipolar) parents will eventually develop one of the affective disorders, and although it is a lifetime risk, about half will be affected between the ages of 15 and 25.

In further research, a study of volunteer pairs of twins disclosed that if one of the pair was sensitive to arecoline, the other was, too--suggesting that the sensitivity could be inherited.

Now the scientists are looking for volunteers in a risk group--in this case with manic-depression in one or both parents--for a new study that they believe may provide a "marker" to identify future affective illness in genetically vulnerable groups.

"Because the sleep procedure is cumbersome," says Nurnberger, "we are also exploring other ways of determining super sensitivity to acetylcholine, possibly involving the measurement of acetylcholine receptors in skin and blood cells. It appears," he says, "that the number of receptors may be related to vulnerability to depression."

Subjects will be followed for about a decade to test the thesis. Some of them may also be tested for a biochemical sensitivity to light, another possible predictor of depressive illnesses.

For this study volunteers should be healthy, between the ages of 15 and 25, with one or both parents having suffered from manic-depressive illness severe enough to cause impairment or incapacitation.

Volunteers will be paid for their time and stand to benefit from the Institute's resources, should they be needed. Volunteers should phone: Mrs. Joel Hamovit, 301-496-3465.

For the child-rearing study, Dr. Marian Yarrow, chief of the NIMH Laboratory of Developmental Psychology, is looking for normal and depressed mothers (even if the depressions are minor). Each mother should have two small children, the youngest between the ages of 15 months and 2 years, and the other between 5 and 8.

Part of the study will take place in a special apartment--described as very home-like and middle class--where the mother and children and their interactions will be observed on three half-days. Yarrow's lab and the apartment are in one of the old estate mansions on the NIH campus in Bethesda. The observations are conducted through one-way screens.

Some 12 to 18 months later another half-day will be spent in the apartment, this time in the afternoon with the father's participation as well.

About 80 families have already taken part in this study, but more are being sought. Volunteers should call: Judy Stillwell at 301-496-4431.

Dr. Norman Rosenthal, an NIMH staff psychiatrist, has been successfully treating a group of people for a depression that comes with the winter and melts along with the snow into a summer euphoria. Now he is interested in any subjects whose moods are affected by seasons in any way, such as those who have depressions in spring or summer and are cheerful in the winter. He is also interested in more volunteers with winter depression to help him find the most efficient time, length and method of shining the light that seems to dispell the winter blues.

Volunteers whose moods change with the weather (or length of the day) should call: 301-496-2141 or write Seasonality Study, National Institutes of Health, Building 10, Room 4S239, 9000 Rockville Pike, Bethesda Md. 20205.