The dopamine hypothesis survives, but there must be a way ahead

How CATIE brought us back to Kansas: a critical re-evaluation of the concept of atypical antipsychotics and their place in the treatment of schizophrenia

The subdivision of the class of antipsychotic drugs into two discrete groups – ‘conventional’ (or first generation) and ‘atypical’ (or second generation) – has been adopted as standard, with the latter generally accepted as ‘better’ and widely recommended as automatic first-line choices. However, this perception has been thrown into confusion with the results of large pragmatic trials that failed to identify advantages with the new, more expensive drugs, while identifying worrying tolerability issues. This article explores the origins of ‘atypicality’, its construction on the back of a confusing and weak clinical validator (diminished liability to promote parkinsonism) and how even in relation to the archetypical atypical, clozapine, the uncertain boundaries of drug-induced extrapyramidal dysfunction may be contributing to confusion about ‘efficacy’ and ‘tolerability’. It argues that abandoning atypicality would open up clinical practice to all drugs of a single class of ‘antipsychotics’ and allow for individualised risk/benefit appraisal as a basis for truly tailored treatment recommendations.

Role of genotype in brain dopamine metabolism and dopamine-dependent behavior of mice

In mice of eight inbred strains--BALB/c, AKR/J, DBA/2, CBA, C57B1/6, DD, CC57Br, and C3H/He--brain dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), in striatum and nucleus accumbens with tuberculum olfactorium, the structures of two main dopaminergic systems--nigrostriatal and mesolimbic--were determined. In both dopaminergic regions, no strain effect on either dopamine or DOPAC levels was found, while for HVA content a highly significant hereditary determination was shown. Influences of selective D1 and D2 dopamine receptor agonists--SK&F 38393 and quinpirole, respectively--as well as that of a mixed D1/D2 agonist, apomorphine, on general locomotor activity and stereotypic climbing were studied. By that, marked genotypic differences in dopamine-dependent behavior and dopamine receptor sensitivity were observed. Although both SK&F 38393 (5 mg/kg) and apomorphine (0.25 mg/kg) decreased locomotion, the effect being genotype dependent, in all strains of mice quinpirole (2.5 mg/kg) proved more potent in locomotor inhibition. SK&F 38393 (10 mg/kg) induced climbing, but 2.5 mg/kg apomorphine in most strains was much more effective. At the same time, quinpirole (up to 8 mg/kg) failed to induce this behavior. This suggests the crucial role of D1 receptors in the generation of climbing, attracting, at the same time, attention to the importance of D1/D2 interaction. The observed drastic interstrain differences in dopamine receptor sensitivity demonstrate the essential role of genotype in the effects of dopaminergic drugs.

The relationship of environmental temperature to the incidence and outcome of schizophrenia

This paper presents new analyses of data from two multicentre studies carried out by the WHO. The morbid risk of developing schizophrenia, as broadly defined by the Determinants of Outcome Study, was positively related to the mean daily range of temperature. The outcome of schizophrenia, as determined by the International Pilot Study of Schizophrenia, was found to be positively related to mean environmental temperature. Further studies are needed to examine the relationship of geographical and climatic variables to schizophrenia in order to complement what is already known about the role of sociocultural factors.

Smithkline Beecham Prize for Young Psychopharmacologists: A review of the relationship between calcium channels and psychiatric disorders

The symptoms and etiology of most major psychiatric disorders probably represent an underlying disturbance of neurotransmitter function. Understanding the mechanisms which control neurotransmitter function, and in particular neurotransmitter release, is therefore of considerable importance in determining the appropriate pharmacological treatment for these disorders. Calcium entry into neurons triggers the release of a wide range of neurotransmitters and recently our understanding of the mechanisms which control neuronal calcium entry has increased considerably. Neuronal calcium entry occurs through either voltage-sensitive or receptor-operated calcium channels. This article reviews the different subtypes of calcium channel, with particular reference to their structure; drugs which act upon them; and the possible function of the subtypes identified to date. In addition, it reviews the potential role of calcium channel antagonists in the treatment of a wide range of psychiatric disorders, and concludes that these drugs may have an increasing therapeutic role particularly in the treatment of drug dependence, mood disorders and Alzheimer's disease.

The estimated density of D2 striatal receptors in schizophrenia. A study with positron emission tomography and 76Br-bromolisuride

The striatal D2 receptors of 19 untreated schizophrenics and 14 normal control subjects were investigated with PET and 76Br-bromolisuride. The ratio of radioactivity in the striatum to that in the cerebellum was taken as an index of the striatal D2 receptor density. There was no significant difference between the control and the schizophrenic groups, nor any difference between subgroups of patients defined by clinical type or course of illness, and no relationship between the striatum:cerebellum activity ratio and SANS or SAPS ratings of symptoms. Unlike in the controls, this ratio was not correlated with age in schizophrenics. This study suggests that there is no quantitative abnormality of striatal D2 dopamine receptors in schizophrenia.

G proteins (Gi, Go) in the medial temporal lobe in schizophrenia: preliminary report of a neurochemical correlate of structural change

We have measured the amount of Gi (the inhibitory G-protein) or Go (a similar G-protein of unknown function) in 5 areas of the medial temporal lobe of control and schizophrenic brains utilizing pertussis toxin-catalyzed ADP ribosylation. The material used has previously been shown to have asymmetrical structural abnormalities of the ventricular system. The amount of Gi or Go was reduced on the left side in the hippocampus, amygdala and parahippocampal gyrus, the difference reaching significance in the hippocampus. This data is the first report of a neurochemical correlate of the structural change in the brains of patients with schizophrenia. Decreased Gi or Go in hippocampus may relate to other reported neurochemical deficits or other transmembrane signalling abnormalities. Further investigations of these indices of secondary messenger function in relation to structural changes are indicated.

Increased forskolin binding in the left parahippocampal gyrus and CA1 region in post mortem schizophrenic brain determined by quantitative autoradiography

Using quantitative autoradiography of [3H]forskolin we have visualized the activated states of adenylate cyclase in the hippocampal formation bilaterally in sections from schizophrenic brain and age-matched controls. There is a generalized increase in binding in schizophrenic hippocampi, particularly in the CA1 region and parahippocampal gyrus. The effect is particularly marked in the left parahippocampal gyrus. These findings add some support to the notion of schizophrenia as a medial temporal lobe disorder and suggest novel substrates as therapeutic targets in schizophrenia.

G-proteins (Gi, Go) in the basal ganglia of control and schizophrenic brain

We detected the existence of Gi (the inhibitory G-protein) or Go (a similar G-protein of unknown function) in the striatum of control and schizophrenic brains utilizing pertussis toxin-catalyzed ADP ribosylation. The level of Gi/Go was significantly decreased by 42% in the putamen of the left hemisphere in schizophrenics; caudate head and globus pallidus levels were unchanged. Decreased Gi or Go may underlie enhanced dopamine function in the schizophrenic brain.

Quantitative autoradiographic analysis of glutamate binding sites in the hippocampal formation in normal and schizophrenic brain post mortem

Using quantitative autoradiography, the anatomical distribution of the binding sites (kainate, N-methyl-D-aspartate and quisqualate) for the excitatory neurotransmitter glutamate has been established in the hippocampal formation from control and schizophrenic brains, post mortem. There is a loss of the kainate subtype particularly in schizophrenic hippocampi mainly from the CA4/CA3 mossy fibre termination zone of the cornu ammonis (CA4 and CA3; control and schizophrenic left hippocampus, respectively, 54.2 and 66.6 pmol/g; 18.3 and 17.9 pmol/g), as well as bilateral losses in the dentate gyrus (left 14.2 pmol/g and right 28.0 pmol/g; left 9.5 pmol/g and right 7.9 pmol/g, control and schizophrenic, respectively) and parahippocampal gyrus (left 50.8 pmol/g and right 41.7 pmol/g, left 27.7 pmol/g and right 25.3 pmol/g, control and schizophrenic, respectively). There is complete preservation of N-methy-D-aspartate sites in schizophrenic hippocampi, and a marginally significant loss of the quisqualate binding site in CA4/CA3 regions (left 249 fmol/g and right 306 fmol/g, left 157 fmol/g and right 148 fmol/g, control and schizophrenic, respectively). These findings reflect the possible importance of glutamate in the pathophysiology of schizophrenia and represent novel targets for therapeutic manipulation in schizophrenia.

Transient recurrence of auditory hallucinations during acute dystonia

Three schizophrenic patients who had transient recurrence of auditory hallucinations during acute dystonia precipitated by neuroleptic medication are reported. If it is accepted that psychotic symptoms result from dopaminergic overactivity, such phenomena suggest that acute dystonia might also have been caused by increased dopaminergic neurotransmission in these cases.

Sight and insight: brain dopamine receptor occupancy by neuroleptics visualised in living schizophrenic patients by positron emission tomography

There can be few more impressive sights in contemporary neuroscience and biological psychiatry than the imaging of neurotransmitter receptors in the brains of living human subjects by positron emission tomography (PET; Sedvall et al, 1986). How has such technology advanced our understanding of the pathophysiology and/or treatment of major psychiatric disorders?

Can the supersensitivity of rodents to dopamine be regarded as a model of tardive dyskinesia?

1. The paper presents arguments derived from both, clinical work and animal experiments, for or against the traditional hypothesis suggesting that tardive dyskinesia (TD) is caused by supersensitivity to dopamine. The main aim of this study was to answer the question posed in the title - whether the supersensitivity to dopamine evoked in rodents by neuroleptics can be regarded as an adequate pharmacological model of TD. 2. The data presented here prove that chronic administration of neuroleptics to schizophrenic patients cannot be the only factor inducing TD; furthermore, symptoms similar or identical to those of TD are also observed in the course of other disorders, not connected with neuroleptics, e.g. aging or schizophrenia itself. 3. Clinical data offer no clear evidence for the existence of a direct cause-effect relationship between super-sensitivity to dopamine and occurrence of TD. 4. The role of brain degeneration, caused by different factors but in particular by the process of aging, in the pathogenesis of dyskinetic disorders, including TD, has been stressed. 5. Pharmacological and biochemical data show that chronic administration of classic neuroleptics to animals induces an increase in the density of dopamine D-2 receptors (Bmax). It seems that this receptor-mediated supersensitivity may concern both the postsynaptic and the presynaptic D-2 dopamine receptors. On the other hand, it is not clear enough whether a dopamine D-1 receptor-mediated supersensitivity might also be a causal factor of TD. 6. The analysis in animals, of biochemical and pharmacological effects of neuroleptics which do not induce TD showed that in some situations these drugs may also evoke the receptor-mediated supersensitivity concerning dopamine D-2 receptors. 7. The method of a prolonged (approx. 1 year) oral administration of neuroleptics seems to differentiate those which induce TD from those which do not, at least regarding the induction of an increase of Bmax for butyrophenone neuroleptics and an increase of apomorphine-induced stereotypy, however, some exceptions are noted. 8. The above analysis of clinical and experimental data suggests that the supersensitivity to dopamine in rats treated chronically with neuroleptics cannot be accepted as a model which reflects the etiopathogenesis of TD. Neither a positive nor a negative result obtained in this test is reliable enough, and either depends on the tested parameters (apomorphine stereotypy and [3H]spiperon binding seem to be the most reliable), route of neuroleptic administration, duration of treatment and, probably, a number of other, still unknown factors.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuroleptic-resistant schizophrenics

According to Crow's postulated positive-negative distinction, negative symptoms of schizophrenia are less responsive to neuroleptic drugs. Not all research evidence supports that expectation, however, so that neuroleptics need not be withheld from any schizophrenic patients. Other aspects of Crow's hypothesized distinction have indicated possible promising results, but more research is required.