Hormones, dopamine receptors and schizophrenia

Prolactin and TSH responses to TRH and to haloperidol in schizophrenic patients before and after treatment

The prolactin (PRL) and the TSH responses to thyrotropin releasing hormone (TRH, 0.4 mg i.v.) and to haloperidol (5 mg i.m.) were studied in 11 male schizophrenic patients in a drug-free state and after treatment with haloperidol, 60 mg daily. The PRL responses observed after i.m. haloperidol in the drug-free state, on average 35.4 ng/ml, were abolished after treatment, indicating complete receptor blockade, while the PRL responses to TRH were preserved, although moderately reduced (from 19.4 to 14.8 ng/ml on average). The TSH responses to TRH were unaltered by the treatment (means 8.25 and 7.74 mIU/l). The results show that the TSH and partially the PRL releasing actions of TRH are not mediated via receptors that are effectively blocked by haloperidol.

Noradrenergic and dopaminergic interrelation in schizophrenia

Growth hormone (GH) and prolactin (PRL) responses to the acute administration of clonidine (150 micrograms) and apomorphine (0.5 mg) were investigated in parallel in 20 drug-free subchronic and chronic schizophrenic patients and in nine control subjects. Neither basal levels of the two hormones nor their mean responses to both stimuli differed significantly between the two groups. However, eight patients had blunted GH responses to clonidine and seven to apomorphine; only two patients showed blunted GH responses to both stimuli. The blunted GH response to apomorphine correlated with the chronicity of the disorder. A greater than normal GH response to clonidine stimulation was observed in paranoid patients. Significant correlations were observed between negative symptoms and GH responses to clonidine (negative), between negative symptoms and PRL responses to apomorphine (positive), and between positive symptoms and PRL responses to apomorphine (negative).

Reduced concentrations of galanin, arginine vasopressin, neuropeptide Y and peptide YY in the temporal cortex but not in the hypothalamus of brains from schizophrenics

Postmortem investigations were performed in brains from 14 schizophrenic patients and 21 controls matched for age and autopsy latency. Concentrations of galanin, delta-sleep-inducing peptide (DSIP), corticotropin-releasing factor (CRF), arginine vasopressin (AVP), neuropeptide Y (NPY) and peptide YY (PYY) were determined in the hypothalamus and grey matter from the temporal cortex. A significant positive correlation between age and the concentrations of galanin and CRF was found in the controls. No sex differences were found except a higher mean of CRF in the hypothalamus of the women. In the temporal cortex of the schizophrenic brains, galanin, AVP, NPY and PYY were significantly reduced. DSIP reduction only bordered on significance. CRF was not reduced. Comparing neuroleptic-treated vs non-treated schizophrenics, the treatment factor could not explain the reduced concentrations of neuropeptides in the temporal lobe. A comparison of controls with schizophrenics showed no significant differences in hypothalamic neuropeptide concentrations.

The relationship of negative schizophrenia to parkinsonism

The positive-negative distinction of schizophrenia has emerged as a valid means of clarifying its heterogeneity. Despite evidence that the two symptom classes may reflect different dimensions of the disease, there is presently no integrated model for understanding of the pathophysiology of these symptoms and their co-occurrence in schizophrenia. We propose that negative phenomena of schizophrenia may be a variant of Parkinsonism. This view is supported by the overlap with Parkinsonism in terms of clinical features, neurochemistry, pharmacology, as well as neuroradiological and neuropathological aspects. As such, negative symptoms may be a manifestation of disease of the basal ganglia and constitute the core pathology in schizophrenia. Positive symptoms, conversely, may reflect an "accessory" process related to a compensatory increase in striatal and limbic dopamine activity following an injury to the dopaminergic system. In the present communication we present a series of studies that support the association of negative schizophrenia and Parkinsonism. Based on this evidence, we suggest that schizophrenic patients with prominent negative symptoms might be managed like patients with Parkinson's disease, namely, with dopaminergic drugs and MAO-B inhibitors. Finally, the association of negative schizophrenia with Parkinsonism raises the possibility that adrenal medullary tissue transplantation, which may benefit a selected group of Parkinsonian patients, may be a future promising therapy for refractory negative schizophrenia.

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.

Effect of oral administration of haloperidol on plasma thyrotropin concentrations in men

To investigate the effects of neuroleptics on plasma thyrotropin (TSH) concentrations, haloperidol tablets were administered orally to 34 normal male volunteers. Seventeen of the subjects received 4 mg; the other 17 received 10 mg. Plasma samples were collected at baseline and 1, 3, 4, 6, 14, 24, 36, 48, 72 and 96 hr after drug administration. Plasma TSH was assayed by a double antibody radioimmunoassay procedure. A significant change in plasma TSH occurred for all subjects (p less than 0.001). By multivariate analysis of variance, the dose x time interaction was not significant. However, a significant dose x time interaction was detected in a univariate analysis. After haloperidol 10 mg a statistically significant rise in TSH occurred at 3-4 hr, which corresponded to the time of attainment of maximal plasma haloperidol concentrations. A significant but modest correlation between plasma haloperidol and TSH was present at 3 hr (0.373; p less than 0.05). TSH concentrations at 14 hr after the 10 mg dose were not significantly correlated with simultaneous or peak plasma haloperidol concentrations. Consequently, only the release of TSH occurring at 3-4 hr after the 10 mg dose was attributed to the drug's effects.

Apomorphine in the evaluation of dopaminergic function in man

1. Apomorphine (Apo), a short acting dopamine (DA) receptor agonist, stimulates growth hormone (GH) secretion, decreases prolactin secretion, induces yawning, penile erections and other physiological effects in man. An effect on behavior, movement disorders and alcoholism has also been described. 2. Apo-mediated responses are used to evaluate DA function in psychiatric and neurological disorders. Many of the studies in schizophrenia using the GH response to Apo as an index of central DA function are difficult to interpret because of failure to control for key variables. 3. The GH response to Apo is a useful system to evaluate the effects of various drugs including peptides which may not cross the blood brain barrier on DA function in man. 4. Apo is a potent sedative. Specific antimanic, antischizophrenic, and anticraving effects in alcoholics have not been convincingly demonstrated. Side effects of Apo and failure to use active placebo make double-blind studies difficult. 5. Apo improves parkinsonian symptoms and certain forms of reflex epilepsy but beneficial effects in other involuntary movement disorders requires further documentation. 6. Apo may be a useful agent to evaluate DA function in impotent patients and predict a therapeutic response to long-acting dopaminergic agents. 7. Impairment of DA function may play a role in diabetic impotence. 8. The development of a simple polygraphic method to monitor the yawning response to Apo may facilitate clinical studies on the basic physiology of yawning in man and the use of the yawning response as a measure of central DA function in schizophrenia and other clinical disorders. 9. The use of Apo with 18F-fluorodeoxyglucose positron emission tomography to examine regional DA function in man opens up a promising area of research. 10. Though long-acting orally active aporphine DA agonists and antagonists have been developed the problem of tolerance may limit their therapeutic potential.

Reduced growth hormone response to apomorphine in schizophrenic patients with poor premorbid social functioning

The apomorphine-induced growth hormone (GH) response of 16 drug-free schizophrenic patients and nine control subjects were studied. The subgroup of nine patients with poor premorbid psychosocial functioning had a significantly lower GH response than the controls. Additional evidence for state dependent effects is provided.

Effects of psychotropic drugs on neurotransmitters in man

Primary biochemical profiles of antidepressants and neuroleptics are summarized in comparison to their actual effects on monoamine neurotransmitters in humans during the time period when clinical response emerges. Even the most biochemically specific of these drugs produces effects on at least two monoamines by three to four weeks. Interestingly, taking into account relative changes in dopamine and serotonin metabolites in cerebrospinal fluid relates better to the primary biochemical action(s) of each drug than do absolute changes. Moreover, monoamine changes after drugs are in the opposite direction to those after ECT, suggesting that balance among rather than shifts in single neurotransmitters is the relevant target of major psychotropic drugs.

Growth hormone response to apomorphine and diagnosis: a comparison of three diagnostic systems

Our study takes a further look at the apomorphine test in the psychoses and affective disorders, with special reference to the use of different diagnostic systems. Patients meeting Research Diagnostic Criteria (RDC) for schizophrenia, schizoaffective disorder, or manic disorder were included. In addition to the RDC, diagnosis was also made using the DSM-III and ICD-9. All patients underwent an evaluation of peak GH response to apomorphine administration. The results show that RDC and ICD-9 are similar, in that for both systems, a high GH response correlates with a schizoaffective disorder and distinguishes those patients significantly from manic patients. The DMS-III brings in some new dimensions, in that schizophreniform disorder (6-month cut-off) is distinguished from schizophrenia. In addition, patients with affective symptoms and mood-incongruent psychoses are more closely related to schizophreniform disorder than to classical manic disorder.

Plasma growth hormone response to oral l-dopa in infantile autism

In order to assess further the occurrence of hypothalamic dysfunction in infantile autism and its possible relationship to dopaminergic abnormalities, the l-dopa provocative test was performed in 22 patients fulfilling DSM-III criteria for this disorder. The results indicate a high incidence (at least 30%) of blunted plasma growth hormone (GH) responses following oral administration of l-dopa in this sample. These data suggest an alteration of hypothalamic dopamine receptor sensitivity in the patients with blunted responses. Thus, a subgroup of autistic patients within a descriptively homogeneous diagnostic category shows evidence of hypothalamic dysregulation and dopaminergic abnormalities.

Effects of apomorphine on blood levels of homovanillic acid, growth hormone and prolactin in medicated schizophrenics and healthy control subjects

Two doses of apomorphine (0.005 mg/kg as a subcutaneous injection and 0.015 mg/kg as a 90 min i.v. infusion), and corresponding placebo treatments, were administered to 11 chronic medicated schizophrenic patients and to 8 healthy control subjects. The purpose of the study was to asses the usefulness of drug-induced alterations in the concentration of homovanillic acid (HVA) in plasma as indicators of dopamine autoreceptor sensitivity in the central nervous system. Growth hormone and prolactin in serum were also measured and used as indicators of postsynaptic dopaminergic drug effects. In the control subjects, i.v. apomorphine increased growth hormone in serum from 1.8 +/- 0.2 to 28.3 +/- 4.6 ng/ml and reduced prolactin by 57 +/- 7%. In the patients, apomorphine caused only weak neuroendocrine effects. HVA in plasma was not affected by apomorphine in either group of subjects. The results for growth hormone and prolactin indicate that postsynaptic dopamine receptors in the tubero-infundibular system are antagonized to a considerable degree also during chronic treatment with neuroleptics. The lack of effect of apomorphine on HVA levels suggests that HVA in plasma is not a sensitive indicator of the inhibition of dopamine release caused by small doses of apomorphine and mediated through dopamine auto-receptors. Supersensitivity of this class of receptors could not be demonstrated in our patients, which contrasts with some earlier results.

Concurrent use of REM latency, dexamethasone suppression, clonidine, and apomorphine tests as biological markers of endogenous depression: a pilot study

In a sample of 12 major depressive inpatients, endogenous subtype (8 primary and 4 secondary) defined by Research Diagnostic Criteria, we compared the sensitivity of four potential biological markers: latency of rapid eye movement (REM) sleep (recorded during at least 4 consecutive nights), dexamethasone suppression, and the clonidine and apomorphine tests. Shortened REM latency (less than 50 minutes during at least 1 night) identified 67% of depressives (87% of primary and 25% of secondary); nonsuppression after dexamethasone identified 50% of depressives (62% of primary and 25% of secondary); blunted growth hormone (GH) response after clonidine identified 75% of depressives (100% of primary and 25% of secondary); and blunted GH response after apomorphine identified 42% of depressives (62% of primary and 0% of secondary). Ninety-two percent of patients were correctly identified by at least one biological marker (100% of primary and 75% of secondary depressives). Of 67% of patients positive on at least two biological markers, all were primary depressives (100%). These four biological markers do not necessarily identify the same population, suggesting that their concurrent use may yield the highest level of diagnostic sensitivity.

Neuroendocrine effects of apomorphine in chronic schizophrenic patients under long-term neuroleptic therapy and after drug withdrawal: relations to psychopathology and tardive dyskinesia

The sensitivity of the dopaminergic hypothalamic pituitary system, as indicated by growth hormone (GH) release after apomorphine (0.5 mg SC), was studied in 11 chronic schizophrenic in-patients under long-term neuroleptic (NL) therapy and after 12 and 30 days' drug withdrawal. GH peak levels after a 12-day drug-free period were significantly elevated (13.1 +/- 12 ng/ml) as compared to NL therapy (4.6 +/- 6.1 ng/ml). Controls showed a significant higher mean peak GH response (13.6 +/- 10 ng/ml) compared to chronic schizophrenic patients under long-term NL therapy. The GH response of patients with symptoms of tardive dyskinesia (TD) did not differ significantly from that of patients without signs of TD. The prolactin (PRL) serum levels under long-term NL treatment were within the normal range in male schizophrenics but decreased significantly after 12 days' drug withdrawal. The data presented indicate a reduced sensitivity of the hypothalamic-pituitary dopamine receptors under long-term NL therapy. The significant increase in GH response on day 12 probably corresponds to a readjustment from a mostly blunted GH response under NL therapy back to stimulated levels of normal controls. No supersensitivity of the pituitary dopamine receptors could be detected.

Serum prolactin response to chlorpromazine and psychopathology in schizophrenics: implications for the dopamine hypothesis

The prolactin (PRL) response to 12.5 and 25 mg of chlorpromazine (CPZ) was studied in unmedicated schizophrenic patients and normal control subjects. Both doses produced significant increases in serum PRL levels compared to saline, but the response to 25 mg CPZ was significantly greater than that to 12.5 mg. The PRL response to the 12.5 mg dose only was significantly correlated with baseline PRL levels for both males and females, suggesting that endogenous dopamine release from tuberoinfundibular neurons has a much greater effect upon the PRL response to the 12.5 mg dose of CPZ than to the 25 mg dose. Both doses of CPZ tended to show lower PRL responses in the schizophrenic females. The PRL response to the 25 mg dose was negatively correlated with ratings of severity of delusions at the time of study. The PRL response to 25 mg correlated highly with the morning serum PRL levels following treatment with CPZ 100 mg and 200 mg orally b.i.d. for 1 week at each dose. The PRL response to both doses did not predict clinical response at the end of 2 weeks of treatment with fixed dosages of CPZ. Serum PRL levels during treatment with CPZ 200 mg b.i.d. were significantly negatively correlated with ratings of hallucinations. The negative correlations between severity of delusions and hallucinations and various PRL measures suggest that increased dopaminergic activity in the tuberoinfundibular hypothalamic-pituitary axis may be associated with increased activity of subcortical and cortical dopaminergic systems.

Effect of cholecystokinin on self-stimulation behavior in rats

Experiments were performed to examine the effects of intracerebroventricularly administered cholecystokinin octapeptide sulfate ester (CCK-8-SE) and unsulfated cholecystokinin octapeptide (CCK-8-NS) on electrical self-stimulation behavior elicited from the medial forebrain bundle. CCK-8-SE and CCK-8-NS in 80 pmol doses reduced the response rate of self-stimulation behavior 22-30 min following injection, while 400 pmol doses of these peptides attenuated self-stimulation behavior between 13 and 36 min. It is suggested that CCK-8-SE and CCK-8-NS interact with central rather than peripheral nervous mechanisms.

The relationship between prolactin levels and clinical ratings in manic patients treated with oral and intravenous test doses of haloperidol

Twelve manic patients were treated for 2 weeks with oral haloperidol; in 6 patients treatment commenced with intravenous haloperidol, and intravenous 'test' doses were given after 1, 3-5 and 14 days of oral medication. From 24 hours to 14 days baseline serum prolactin levels rose towards a plateau, as did the improvement in clinical ratings. After the first intravenous test doses of haloperidol, prolactin levels peaked at 1 hour; however, they fell to a low point at 24 hours, and no response to further test doses was seen for 3-5 days. The response tended to return at 14 days. The mechanisms underlying the changes in prolactin levels, and in clinical state, are discussed.

Low-dose apomorphine reduces serum homovanillic acid concentrations in schizophrenic patients

This study was carried out to evaluate the postulated dopaminergic auto-receptor regulatory effect in man of low-dose apomorphine. Behavior and serum homovanillic acid concentrations following low-dose apomorphine were investigated. Five medicated chronic schizophrenic patients had serum homovanillic acid concentrations measured by mass fragmentography before and after 0.005 mg/kg of apomorphine or saline placebo. Results demonstrate significant reductions in serum homovanillic acid concentrations in all five subjects following apomorphine as compared with placebo. These findings present direct evidence of a specific dopamine autoreceptor effect of low-dose apomorphine in schizophrenic patients.