Biomedical subjects
Publications and source records attributed to S Gershon.
Acute i.v. infusion but not daily oral administration of thioridazine-HCl in the dog produced EKG anomalies similar to those reported in psychiatric patients taking this drug. Lack of EKG effects after thioridazine-5-sulfoxide infusion and presence of anomalies after thioridazine at equivalent doses suggests further evaluation of the relationship between reported plasma levels of thioridazine and its ring-sulfoxide in association with EKG changes.
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The effects of the antipsychotic/antidepressant drug CI-686 on apomorphine- and amphetamine-induced stereotypies, dopamine metabolism, neuroleptic binding, and serum prolactin levels were determined. CI-686 displayed profiles of activity in each of these systems that differs markedly from those of other antipsychotics. CI-686's unique preclinical profile suggests a mechanism of action other than dopamine antagonism which could have implications regarding current thinking on the pathophysiology of schizophrenia.
Low doses of the dopamine agonist ET-495 were administered to nonpsychotic volunteer subjects by slow intravenous infusion, followed by a bolus of 1.5--2.5 mg haloperidol. ET-495 caused progressive dysphoria and sedation (in some cases, light sleep), effects believed to be mediated by dopaminergic inhibition. However, ET-495 also elevated growth hormone and suppressed prolactin, typical responses to dopamine agonist activity. Haloperidol reversed both the sedation and prolactin suppression induced by ET-495. These findings suggest: (1) that the sedation and hormonal responses were produced by stimulation of dopamine receptors; (2) that neurotransmitter systems mediating behavioral and neuroendocrine regulation may have differential neuropharmacological characteristics.
In an open study of 8 subjects, approximately half showed some attenuation of CNS stimulant effects of amphetamine after pretreatment with lithium. Two showed specific blockade of euphoria, with persistence of some CNS stimulant effects. In 3 subjects lithium did not appear to affect the response to amphetamine. Lithium caused significant attenuation of the amphetamine-induced increase in systolic blood pressure for the group as a whole.
Apomorphine, a direct-acting dopamine agonist, stimulates release of growth hormone (hGH) and suppresses release of prolactin (PRL) from the anterior pituitary. Previous studies comparing the magnitude of these responses in schizophrenics and controls suggest that many acute (and some chronic) schizophrenics have exaggerated hGH responses; many chronic schizophrenics (and patients with tardive dyskinesia) have blunted hGH responses to apomorphine, and possibly blunted PRL responses. The present studies extend and confirm these findings in chronic schizophrenics; in addition, several studies were undertaken to further characterize these apomorphine-induced endocrine responses. Studies in which apomorphine was given on 2 or 3 separate occasions to each of five subjects indicate that the hGH response is a highly reproducible individual index, but PRL suppression is a less satisfactory measure. hGH responses to apomorphine were consistently antagonized by pretreatment with haloperidol, supporting the concept that the hGH-releasing effect of apomorphine is mediated by its action on dopamine receptors. Cyproheptadine pretreatment was associated with erratic increases or decreases in the hGH response to apomorphine, but did not alter PRL levels or apomorphine-induced PRL suppression. The relationship of these findings to biological hypotheses of schizophrenia and to neuroleptic-induced receptor changes is discussed.
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