Differential prolactin responses to haloperidol and TRH in normal adult men

Prolactin responses to im haloperidol in drug-naive and drug-experienced schizophrenic patients

The prolactin (PRL) responses to 5 mg im haloperidol were assessed in the drug-free state and after one month treatment with neuroleptics in 14 male schizophrenic patients who had never received drug treatment, and in 20 male patients who had discontinued their neuroleptic treatment for periods of two months to one year. Drug experienced patients showed lower PRL increases after acute haloperidol (mean 31.7 ng/ml) than drug-naive patients (mean responses 43.4 ng/ml). After treatment with neuroleptics in doses appropriate for the best clinical response, the baseline PRL levels were similar in the two groups, and im haloperidol did not cause any further PRL increases. The results provide evidence that after discontinuation of neuroleptics, the hypothalamic-pituitary dopamine receptors are subsensitive, and remain in that state for long periods of time.

Dopaminergic modulation of working memory for spatial but not object cues in normal humans

It appears that functionally segregated visual pathways exist in the primate brain for the processing of visuospatial versus nonspatial information. Functional segregation has been demonstrated for the early associative processing of sensory information but may also exist at higher levels of cognitive analysis. Namely, connections between the dorsal visual system and dorsolateral prefrontal cortex (PFC) appear to mediate spatial working memory, which is modulated by dopamine receptor fields in the principal sulcal region of the PFC. It is speculated that nonspatial working memory may be modulated within connections between ventral visual processing regions and the inferior convexity of the PFC. Whether dopamine facilitates nonspatial memory through connections between the ventral visual system and ventral PFC has not been examined. In this study, normal humans completed spatial and nonspatial working memory tasks under pharmacological challenges with a dopamine receptor agonist (bromocriptine) and antagonist (haloperidol) in a double-blind placebcxontrolled repeated measures design. Findings indicated facilitation of spatial delayed working memory functions by bromocriptine and impairment of spatial working memory functions by haloperidol. Neither drug was effective in manipulating nonspatial memory performance. Control tasks were included to measure drug effects on basic sensorimotor and attentional processes. Findings suggest that separate processing mechanisms for remembering "What" versus "Where" an object is may exist at structural, but also neurochemical, levels in the human brain.

Changes in central serotonergic function as a correlate of duration of illness in paranoid schizophrenia

There is evidence that the duration of untreated psychosis may affect both the course and outcome of treatment in schizophrenic patients. In the present study, we used neuroendocrine probes to test the hypothesis that untreated psychosis may induce time-dependent changes in central serotonergic and dopaminergic neurotransmission. Prolactin responses to the administration of clomipramine (i.v.) and haloperidol (i.m.) were measured in healthy control subjects and in 16 never-treated male patients with DSM-IV diagnoses of schizophreniform or schizophrenic disorders of paranoid subtype, both before and after 5 weeks of treatment with haloperidol. In the drug-free state, schizophrenic patients exhibited significantly increased prolactin responses to clomipramine administration compared with both the healthy control subjects and the schizophreniform patients. Maximum prolactin responses to clomipramine in the total group of patients were positively correlated with the duration of psychotic illness and negatively correlated with changes in Positive and Negative Syndrome Scale (PANSS) total, negative symptoms and general psychopathology scores after 5 weeks of treatment with haloperidol. Prolactin responses to haloperidol challenge in the drug-free state were lower in the schizophreniform group than in the control and the schizophrenic groups, but the differences did not reach statistical significance. The results provide evidence that the persistence of psychotic psychopathology induces secondary neuroadaptive effects, which seem to involve changes in central serotonergic function.

Dopamine receptor responsivity in schizophrenic patients in a drug-free state and after treatment with olanzapine

1. Olanzapine is a novel atypical antipsychotic with affinity for a number of neurotransmitter receptors including dopamine D1, D2, D4, serotonin 5HT2A, 5HT2C, histamine H1, a1-adrenergic, and muscarinic receptors. 2. A neuroendocrinological method to check the degree of dopamine receptor blocking is by measuring the prolactin (PRL) responses to acute (i.m.) administration of haloperidol (HAL). The authors applied this test in a group of male patients with DSM-IV schizophrenia in the drug-free state. The patients were subsequently treated with olanzapine (OLZ) (mean daily dose: 22.5+/-5.8) and the test was repeated six weeks later. For the HAL-test, 5mg HAL were injected i.m. and blood samples were taken at times 0, 30, 60, 90 and 120 minutes. Fourteen patients enrolled in the study. Psychopathology was assessed by means of the Brief Psychiatric Rating Scale (BPRS). 3. Six weeks treatment with OLZ resulted in significant decreases in the total BPRS score and on the score of its subscales for positive, negative, and general psychopathology. Comparison of the PRL response patterns, after HAL administration by analysis of variance for repeated measures (ANOVAR) for drug treatment and time, revealed a highly significant time effect (F=28.98, p=0.000) and a significant treatment by time interaction (F=8.27, p=0.000008). Namely, in the drug-free state significant increases were found in the PRL levels after i.m. HAL administration which were significantly reduced during treatment with OLZ, indicating moderate receptor blockade.

Prolactin secretion in response to haloperidol challenge in delusional (psychotic) and non-delusional depression

Certain studies on measures related to central neurotransmitter activity have demonstrated that in delusional (psychotic) depression there is a dopaminergic dysregulation which distinguishes it from non-psychotic depression. A neuroendocrinologic method to check the degree of DA receptor responsivity is by measuring the prolactin responses to acute intramuscular administration of haloperidol. We studied this possibility by applying the haloperidol test in seven delusional and ten non-delusional depressed patients. All patients met DSM-IV criteria for a major depressive episode, single or recurrent, with or without psychotic features. After a three-week washout period, 5 mg of haloperidol were injected i.m. and blood samples were taken at 0, 30, 60, 90 and 120 minutes. In both trials, significant time effects were observed (elevated prolactin levels, F = 11.36, P = 0.000). However, the prolactin responses to haloperidol did not differ significantly between the two patient groups (F = 0.12, P = 0.97). These data do not show a difference in D(2) receptor responsivity, at least at the hypothalamus-pituitary level, between psychotic and non-psychotic depression.

Influence of the dosing interval on prolactin release after remoxipride

1. The prolactin response following administration of the D2-dopamine receptor antagonist remoxipride was studied in eight healthy male volunteers. The purpose of the study was to investigate the duration of a refractory period of prolactin release following two doses of remoxipride. A further aim was to compare the prolactin response following remoxipride and thyrotropin release hormone (TRH) during the refractory period. The subjects received two 30 min intravenous (i.v.) infusions of remoxipride 50 mg with different time intervals between the two doses, in a randomized six period crossover design. The time intervals between the two remoxipride doses were 2, 8, 12, 24 and 48 h. On one occasion the remoxipride dose was followed by an i.v. injection of TRH after 2 h. 2. The plasma peak prolactin concentrations obtained after the first remoxipride dose correspond to a maximal release of prolactin according to earlier studies. A small second peak of prolactin was observed after 2 h. The release was gradually increased with longer time intervals between the consecutive doses. The refractory period for a second prolactin release similar to the first one after remoxipride was found to be 24 h for most of the subjects. 3. TRH resulted in a faster and higher increase in prolactin response of a shorter duration than after remoxipride administered 2 h after the first dose.

Basal and haloperidol-stimulated prolactin and symptoms of nonaffective and affective psychoses in neuroleptic-free men

The prolactin (PRL) response to 0.5 mg of intravenous haloperidol (HPL) IV may be a measure of tuberoinfundibular dopaminergic activity. Our earlier reports, using multidiagnostic strategies in schizophrenia, suggested that psychoses characterized by the absence of affective syndromes (Keks et al 1990) and the presence of thought disorder and passivity delusions (Keks et al 1992) are linked to blunted PRL responses. In this paper we evaluated the relationships between basal and HPL-stimulated PRL concentrations, and a number of potentially relevant symptom measures. Basal PRL was lower in patients without a depressive syndrome and suicidal ideation. Stimulated PRL was lower in patients without neurovegetative symptoms (versus patients with neurovegetative symptoms and controls), with depression (versus patients with no depression and controls) and those with disorder of associations (versus patients without association disturbance and controls). These findings can be interpreted as indicating a link between endocrine measures of dopaminergic function and a subtype of schizophrenic psychosis characterized by the presence of thinking disturbance in the absence of depression.

Effect of haloperidol on measures of craving and impaired control in alcoholic subjects

We recently proposed that alcoholics suffer from a functional defect within the basal ganglia/limbic striatum or its modulation by dopaminergic projections from the ventral tegmentum, and that inhibition of striatal output caused by the prodopaminergic effects of alcohol ingestion induces or exacerbates craving and impaired control over alcohol consumption in alcoholic individuals. To test this hypothesis, 16 subjects with a diagnosis of alcohol dependence or abuse were studied in a double-blind, placebo-controlled experiment in which the effects of the D-2 antagonist haloperidol on measures of craving and impaired control were assessed before and after administration of a priming dose of alcohol. Subjects were pretreated with 0.015-0.025 mg/kg haloperidol (experimental condition) or 2 ml normal saline (control condition), and subsequently consumed 0.4-0.6 g/kg ethanol as their preferred alcohol-containing beverage. Significant increases in subjectively rated craving for alcohol and perceived difficulty resisting additional alcohol consumption occurred following the priming dose of alcohol when subjects were pretreated with saline. In contrast, no significant changes in reported ability to resist additional alcohol occurred when subjects were pretreated with haloperidol, and reported levels of craving decreased relative to baseline following haloperidol pretreatment. Subjects also consumed about 25% less optionally available alcohol when pretreated with haloperidol than when pretreated with saline. These findings support the hypothesis that craving and impaired control are induced or exacerbated by the prodopaminergic effects of alcohol consumption.

Multidiagnostic evaluation of prolactin response to haloperidol challenge in schizophrenia: maximal blunting in Kraepelinian patients

We have previously reported that prolactin (PRL) responses to haloperidol 0.5 mg IV were blunted in subjects characterized by several diagnostic systems of schizophrenia compared to controls (Keks et al 1990). However, an attempt to find a diagnostic system most different from controls was unsuccessful due to inherent difficulties in the statistical analysis of multidiagnostic data. In this paper we present new methodologies. A test for differences in dependent correlations demonstrated that most of the variance in stimulated PRL was accounted for by Kraepelinian, and least by Schneiderian and M. Bleulerian, schizophrenias (p < 0.001). The main symptomatic difference between nonKraepelinian and Kraepelinian patients was the presence of association disturbance and feelings of passivity. Patients with both symptoms had a lower stimulated PRL than controls. Further findings and possible implications are discussed.

Prolactin responses to haloperidol in drug-free and treated schizophrenic patients

The prolactin response to 5 mg haloperidol i.m. was studied in 12 schizophrenic patients in a drug-free state and after a month treatment with haloperidol, as a possible index of dopamine receptor sensitivity and occupancy. Blood samples were taken at times 0, 60, 90 and 120 minutes. The increase in PRL observed in the drug-free state disappeared after drug treatment. The PRL plasma levels after treatment with 60 mg haloperidol per os were higher than the maximal PRL responses after 5 mg i.m. The increases in baseline PRL caused by the treatment correlated positively to the reduction in the BPRS score. The test was also performed in a group of 11 patients chronically treated with haloperidol during a daily dose of 60 mg, and 15 days after reduction of the dose to 30 mg. PRL increases after 5 mg haloperidol i.m. were observed only after reduction of the dose. It is suggested that the prolactin response to haloperidol is an index of the occupancy of receptors that are involved in the PRL releasing mechanisms, and could be used to verify their blockade by the neuroleptics, especially in patients that do not respond positively to drug treatment.

Relationship of psychotic symptoms to haloperidol-stimulated prolactin release

Prolactin (PRL) response to a single dose of intravenous haloperidol (0.5 mg) was measured as a marker of tuberoinfundibular dopamine (TIDA) activity in 24 neuroleptic-free, male, psychotic patients. The PRL responses were then correlated with psychotic symptoms measured with Andreasen's Scales for the Assessment of Positive and Negative Symptoms (SAPS, SANS). Correlation analyses revealed a significant inverse relationship between PRL response and the severity of delusional symptoms. There was no significant correlation between the symptoms of hallucinations, formal thought disorder, or global negative symptoms and PRL response to haloperidol, nor were there any significant correlations between basal PRL and symptom severity. These results suggest that among the positive and negative symptoms associated with psychoses, only delusions may be associated with TIDA overactivity.

Basal and haloperidol-stimulated prolactin in neuroleptic-free men with schizophrenia defined by 11 diagnostic systems

Forty-four male, neuroleptic-free, acutely psychotic patients with at least one diagnosis of schizophrenia among 11 diagnostic systems, and 28 healthy controls, underwent measurement of prolactin (PRL) concentrations before and after intravenous administration of haloperidol (0.5 mg). Basal PRL concentrations were lower in the patients with Research Diagnostic Criteria (RDC) DSM-III, Cloninger, and Taylor and Abrams schizophrenias than in controls. Compared with the controls, the PRL response to haloperidol was lower in the patients with schizophrenia defined by all diagnostic systems except those of Schneider and M. Bleuler. Neither basal nor stimulated PRL concentrations were correlated with positive symptoms, but basal PRL was correlated with the Brief Psychiatric Rating Scale (BPRS) depression-related subscore. This study lends further support for the presence of dopaminergic dysfunction in schizophrenia, and demonstrates the advantages and problems in the use of multidiagnostic psychopathological evaluation to categorize a disorder where there is major disagreement among diagnostic systems.

Prolactin response to low-dose haloperidol challenge in schizophrenic, non-schizophrenic psychotic, and control subjects

Haloperidol was administered IV to 46 male psychotic inpatients and 28 male control subjects. A two-way analysis of covariance, with age as the covariate, revealed that DSM-III schizophrenics (n = 27) had a lower prolactin response to haloperidol than did the controls (n = 28). There were no significant differences between the prolactin responses in schizophrenics, patients with affective disorders (n = 7), and those with other psychoses (n = 12), which included patients with paranoia, schizophreniform, schizoaffective disorder, and atypical psychoses. These findings support the proposition that tuberoinfundibular dopaminergic dysfunction may occur in certain patients with DSM-III schizophrenia.

Inositol monophosphate esterase inhibition by lithium in normal human studies using neuroendocrine tests. Part I. PRL and TSH responses to TRH

1. Many neuroendocrine events are mediated by intracellularly second messengers, among which are the breakdown of phosphatidylinositol 4,5-biphosphate (PIP2). 2. Lithium (Li) was shown in therapeutic doses to be a specific inhibitor of the enzyme inositol monophosphate esterase Li reduces the turnover of PIP2 and diminishes the cell responses. 3. In order to investigate this new mode of action of Li the authors studied the influence of acute dose of Li on the response of prolactin (PRL) and thyrotropin (TSH) to thyrotropin stimulating hormone (TRH), a stimulation mainly mediated through the activation of the turnover of PIP2. 4. In seven normal subjects a single dose of 19.80 meq of Li reduced the response of PRL in 4, and augmented it in 3 subjects: Li decreased the TSH response in 4 subjects, it was increased in 1 and remained unchanged in 2. 5. These results are discussed in the light of the different interactions between hormone secretion, and the fact that adenopituitary is located out of the brain blood barrier.

Prolactin response induced by ECT and TRH

The prolactin response after ECT in ten female melancholic patients correlated significantly to their prolactin response to i.v. TRH. These findings may suggest an underlying common mechanism between TRH and ECT regarding their PRL releasing properties.