NOTES FROM THE LOG-BOOK OF A PSYCHOPHARMACOLOGICAL RESEARCH UNIT. II

Provocative tests with psychostimulant drugs in schizophrenia

The psychotogenic effects of psychostimulant drugs have provided a major line of evidence in support of the DA hypothesis of schizophrenia. To evaluate the effects of psychostimulant (PS) drug in schizophrenia and the clinical variables which may influence their expression, we reviewed 36 studies of PS drugs in patients with schizophrenia. Approximately 40% evidence a psychotogenic response to PS administration in doses that are subpsychotogenic in normals. Specific clinical variables appear to modify this response, including diagnosis, degree and type of psychopathology, stage of illness and pharmacologic status at the time of testing. Non-amphetamine-like PS drugs, e.g., methylphenidate, appear to have greater psychotogenic potency than amphetamine-like PS drugs. These results suggest the presence of a subgroup of schizophrenic patients who exhibit psychotic symptom activation with PS in a state dependent or independent fashion. This biologic phenomenon may be clinically exploitable and should be investigated further.

Differential response to amphetamine in schizophrenia

Amphetamine added to maintenance therapy with neuroleptic drugs was accompanied by relief of complaints in 32 of 48 chronic schizophrenic patients with a long-standing incapacity for work. In 22 cases this relief was followed by increased work efficiency. These gains were lost at experimental withdrawal of amphetamine. The response to amphetamine varied with type of schizophrenic symptomatology. All current regressive symptoms meant worsening in spite of concomitant neuroleptic treatment, in accordance with the dopamine hypothesis. Non-regressive subjects displaying florid symptoms, however, benefited. Worsening, in a few cases, occurred only in the absence of neuroleptics. A few subjects with negative symptoms only, seemed totally unresponsive. These findings point at variations in sensitivity to dopaminergic stimulation in schizophrenic subjects. Worsening and improvement with amphetamine were each clearly connected with type of symptomatology only when current psychotic or florid non-regressive symptoms were exhibited. In cases with negative symptoms only, the type of response could not be reliably based on clinical data. Studies of autonomic functioning and attention were therefore performed in a sub-sample. Skin conductance level, reactivity and habituation rate were found to be lower in positive responders before amphetamine. After amphetamine there were no such differences. Attention tests showed no initial differences between groups but the performance of positive responders improved with amphetamine.