Pharmacology: the dopamine connection

Article Abstract:

In the September 13, 1990, issue of the journal Nature, researchers report the molecular cloning of a novel receptor for the neurotransmitter dopamine. Clearly distinct from the D1 and D2 receptors, it has been labeled D3. The discovery will probably renew the interest of pharmacologists in the relation between neuroleptic drugs and dopamine. The introduction of chlorpromazine in 1952 began a revolution in psychiatry. Numerous drugs followed; they had a clinically valuable antipsychotic effect and were dubbed neuroleptics. Research into the mechanism of the function of the neuroleptic drugs suggested that they somehow altered dopamine systems within the brain. However, the technology was not yet available for resolving questions about the mode of action of neuroleptics. The introduction of ligand-binding techniques opened the doors for further research. These techniques use radioactively labeled drugs to directly demonstrate where and to what the drugs bind within the brain. Using these techniques, investigators showed that two distinct types of dopamine receptors were present, which resolved some of the enigma of why some neuroleptics blocked dopamine well and others did so poorly. By definition, all dopamine receptors bind dopamine. Butyrophenones, the most potent neuroleptics, bind to the D2 receptor much better than to the D1, and thus may exert a potent effect while showing poor overall blocking of dopamine. Now, the identification of D3 may not only answer more questions, but be of great clinical importance as well. For example, pergolide and quinpirole, both drugs of the class called dopamine agonists have therapeutic effects in parkinsonism (a neurological condition involving involuntary movement and tremor), which were thought to be due to binding to D2. The interaction of these drugs with D3, however, seems to be 30 to 100 times more potent. Since neurological side effects are a major drawback top some neuroleptics, the understanding of the relationships of D1, D2, and D3 to drug effects opens the door for the effective design of a whole new generation of safer and more effective antipsychotic drugs. (Consumer Summary produced by Reliance Medical Information, Inc.)

Identification and classification, Antipsychotic drugs, Antipsychotic agents, Dopamine receptors, editorial

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Diurnal variation in mRNA encoding serotonin N-acetyltransferase in pineal gland

Article Abstract:

The analysis of pineal mRNA from a rat encoding serotonin N-acetyltransferase (NAT) indicates that the expression of this gene increases during the night and gradually decreases during the day. Study of a cDNA library from pineal gland of 200 rats, killed at 2.00 a.m. reveals the presence of a 1.6 kb cDNA encoding 205 amino acids. The diurnal variation in pineal NAT activity shows that cAMP response element binding factor regulate NAT transcription. The cloning of NAT is discussed.

Methods, Cloning, Messenger RNA, Pineal gland

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No endothelial NO

Article Abstract:

Nitric acid produced by the endothelial cells is a potent vasodilator involved in blood pressure and blood flow regulation. Abnormalities in the NO production causes atherosclerosis, diabetes and hypertension. The three main forms of nitric oxide synthase are the neuronal, the macrophage or inducible and the endothelial. The biological functions of nitric oxide are discussed.

Nitric oxide, Endothelium, Cytology

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