A review of nicotinic acid, N-methylated indoleamines and schizophrenia

Altered consciousness states and endogenous psychoses: a common molecular pathway?

Interest in the role of indolamines in the pathogenesis of psychoses has been renewed in recent years by the development of atypical antipsychotic drugs such as clozapine, olanzapine, and risperidone, which act on serotonin receptors. Discovery of the hallucinogenic compounds called methylated indolealkyalamines (MIAs) (e.g. N,N-dimethylserotonin, or bufotenin, and N,N-dimethyltryptamine, or DMT) led proponents of the transmethylation hypothesis of schizophrenia to theorize that through some inborn error of metabolism, serotonin or tryptamine might undergo the addition of extra methyl radicals, thereby forming MIAs with hallucinogenic properties. Various studies have attempted to detect the excretion of MIAs, especially DMT, in the body fluids of psychotic patients and normal controls. Some of these studies have demonstrated elevated MIA concentrations in psychotic patients, including those with schizophrenia, compared with normal persons, and others have not. A number of variables may account for these contradictory findings. The mechanism whereby the beverage ayahuasca, which is used in certain cure and divination rituals in the Amazon Basin, exerts its hallucinogenic effects may serve as a model to explain the mechanism underlying hallucinogenic symptoms in schizophrenia and may lend support to the transmethylation hypothesis. Certain studies suggest that specific perceptual disturbances manifested by schizophrenic patients could contribute to progressive deterioration and negative symptomatology. All these findings point to the need for further study of the neurophysiology of MIAs and their pathogenetic role in endogenous psychoses.

Production of convulsions in mice by the combination of methionine and homocysteine

Behavioral effects of methionine have been attributed to either increased availability of methyl groups for the production of methylated amines or accumulation of convulsive metabolites. If the second hypothesis is correct, methionine would be expected to have convulsive properties either by itself or in combination with subconvulsive dosages of other known convulsants. Methionine alone did not induce convulsions when administered by various routes in dosages of 250--13,000 mg/kg, although larger doses of methionine (500--4,000 mg/kg) decreased behavioral activity. However, methionine pretreatment (125--1,000 mg/kg) markedly enhanced convulsions in animals challenaed with subconvulsine dosages of homocysteine. Pentylenetetrazol was less effective than homocysteine in promoting convulsions in methionine-pretreated animals. Although the convulsive effects of methionine were not shared by other natural amino acids (glutamate, asparate, cysteine, tryptophan, and others), ethionine enhanced homocysteine-induced convulsions almost as effectively as did methionine. Methionine thus promotes convulsions under certain conditions, plerhaps due to an accumulation of homocysteine or of other metabolites with convulsive properties.U

Loose associations: straight and crooked thinking and the group of schizophrenias

In this paper I hope to provide the basis for a discussion on logic, logical thinking and creativity in medicine, particularly in psychiatry. By way of illustration we will examine schizophrenia with particular reference to biochemistry, but the discussion will focus on semantic issues and philosophical concepts. These issues are of fundamental importance in the development of psychiatry both as art and craft. Thus the paper deals both with the study of madness and madness itself. The title of the address illustrates some forms of communication which occur in the schizophrenias. It includes references to other ideas, to formal thought disorder and illogical thinking, private puns, vague links, and pointers to other sources and authors, namely, Bleuler (1950), Ernest Jones (1959) and Thouless (1974). These are all contained in a loose framework, wherein reference is made to a key anomaly always found in, but by no means unique to schizophrenia.