Abstract
One important role of the brain is to maintain the living organism in a normal steady state by responding adequately to the changing demands of both the internal and external environment of the body. Psychosomatic disorders are perturbed states of this regulatory mechanism. Today, knowledge of neurotransmitters and neuromodulators and their receptors is rapidly increasing. Many amines, such as dopamine, noradrenaline, serotonin and acetylcholine, many amino acids and nucleosides, such as glutamate, GABA and adenosine, and many peptides, such as substance P, enkephaline, endorphine, TRH, CCK and others, act as neurotransmitters or neuromodulators. Psychosomatic disorders are closely related to mental activities like anxiety and depression. These mental activities have their biological basis in the central nervous system. Anxiety disorders are suspected of being caused by a disturbance of endogenous anxiogenic substances. Candidates for these substances include noradrenaline, β-pcarboline and lactate. GABA and adenosine, on the other hand, are putative endogenous anxiolytic substances. In anxiety disorders, anxiety attacks are provoked by the administration of the α_2 adrenoceptor antagonist yohimbine and inhibited by its agonist clonidine, indicating the supersensitvity of presynaptic α_2 adrenoceptors in such disorders. Investigation of the benzodiazepine receptor revealed that the receptor is coupled with GABA receptor sites and associated chloride channels, a result that indicates benzodiazepine facilitates GABA related neuronal inhibition. β-Carboline and its derivatives are active antagonists or inverse agonists of benzodiazepine. Caffeine and theophyline are anxiogenic substances which are antagonists of adenosine. On the other hand, carbamazepine has a high afiinity to the adenosine receptors, especially to the A1 receptor in brain tissue. The anticonvulsive and antianxiety effects of carbamazepine may be related to central adenosine function. Depression is frequently provoked by chronic stress. Among patients with major depression, there are many nonsuppressors of the dexamethasone suppression test (DST), indicating a hyperactivity of hypothalamicpituitaryadrenocortical function. The DST is a state-dependent biological index of the severity of symptoms. Depressed patients with high postdexamethasone cortisol levels have high plasma catecholamine levels. The plasma levels of MHPG (3-methoxy-4-hydroxyphenylglycol), a metabolite of noradrenaline, are also increased in depressed patients, many of whom have symptoms of anxiety and agitation. The various states of psychosomatic disorders are most likely based on different kinds of disturbances in the function of neurotransmitters or their receptors. Increased knowledge of the biological basis of such disorders contributes to their treatment.
