Serotonin-Injeel and forte, according to definition and action, can also be included in group C of the intermediary catalysts (q.v.), where, for example, corresponding directions will be found under Histamin-Injeel. The functions of serotonin: stimulation of the smooth musculature, the blood vessels, the bronchial tubes, the intestine and the uterus. In each case according to the initial condition of the circulatory RR-reducing or RR-increasing action (Wilder‘s rule of initial values).

In this connection, the action of serotonin on the coronary-circulatory system is of a very complex nature, as direct and reflex effects make an analysis of the action very difficult.

Serotonin is very greatly increased in the blood of carcinoid patients. Increased elimination of 5-hydroxyindoleacetic acid (serotonin degradation product) in the urine can always be detected.

Apart from the flushes (fitful red-cyanotic coloration of the face and neck), the following symptoms are frequent in these cases: diarrhoea, possibly, at first alternating with spasmodic atonic constipation; attacks of Iycorexia with spontaneous hypoglycemia, polymorphous allergic dermatitis, cyanosis, tachycardia, tachypnea with a tendency toward attacks of asthma but also to attacks of migraine (serotonin or histamine headache in the form of a Bing-Horton syndrome (see above under Histamin-Injeel and forte). Further, in this connection, serotonin can also bring about endocardial fibrosis, with subsequent coronary insufficiency as a result of tricuspidal insufficiency and pulmonary stenosis (alterations, therefore, particularly on the right side of the heart).

Serotonin and substances similar to serotonin can bring about psychotic conditions; on the other hand, investigations with Iysergic acid diethylamide (LSD), an antagonist to serotonin, showed that the psychodysleptic action of LSDis attributable to a repression of the serotonin of the neurone receptors, leading to the appearance of a schizophrenic onset (LSDintoxication).

Indications: To be used experimentally for symptoms and clinical pictures as indicated above, in which disturbances of the serotonin metabolism can play a part; thus, for example, for headaches and the symptoms of a caroinoid syndrome. Allergic and toxic skin affections, e.g. after contact with octopods, salamanders, cuttlefish, mollusks (murex) or stinging nettles.