Drugs, neurotransmitters, and schizophrenia

Anorectic effect of ephedrine

1. Different doses of ephedrine (3.1-50 mg kg-1) were given intraperitoneally to rats and found to decrease food intake dose-dependently. 2. The anorectic effect of ephedrine was decreased by animal pretreatment with pimozide, but phenoxybenzamine, propranolol and methergoline did not decrease the response. 3. The results show that the anorexia produced by ephedrine may be due to indirect dopaminergic mechanism of the drug.

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.

Smooth pursuit eye movement disorder and its psychobiologic correlates in unmedicated schizophrenics

The accuracy of smooth pursuit eye movements (SPEMs) was evaluated electrooculographically in 14 medication-free schizophrenics. Concentrations of monoamine metabolites and gamma-amino-butyric acid (GABA) were measured in their cerebrospinal fluid (CSF). Ventricular-brain ratios (VBR) were determined by computed axial tomography (CT scan). Premorbid adjustment was evaluated by the Phillips Scale. The SPEMs of eight of the patients were reevaluated after 2 weeks of treatment with either prazosin or pimozide. No consistent significant correlations were found between SPEM accuracy and CSF metabolite concentrations, VBR, or premorbid adjustment. SPEM accuracy was not correlated with number of days off medication and was significantly correlated when measured before and during medication.

CGS 10746B: an atypical antipsychotic candidate that selectively decreases dopamine release at behaviorally effective doses

CGS 10746B, a benzothiadiazepine, has a behavioral profile in mice and monkeys similar to the atypical antipsychotic clozapine. Unlike clozapine, CGS 10746B suppresses dopamine neuron firing rates and, when administered at behaviorally effective doses by the oral or intraperitoneal route, decreases neostriatal dopamine release without changing dopamine metabolism or occupying D2 receptors. CGS 10746B is the first atypical antipsychotic candidate that selectively decreases dopamine release.

Two automated locomotor activity tests for dopamine autoreceptor agonists

In the first test (exploratory activity), pretreated rats explored a novel environment in the dark. The potential autoreceptor agonists apomorphine HCl, N-n-propylnorapomorphine (NPA), and N-n-propyl-3-(3-hydroxyphenyl)-piperidine (3-PPP) and its enantiomers decreased the total distance travelled while at the same time paradoxically increasing the number of discrete movements. This is a very different pattern from that of the typical antipsychotic drugs haloperidol HCl and chlorpromazine HCl, and the atypical antipsychotic drug clozapine, which also decreased the total distance travelled but decreased the number of movements. Both groups decreased the distance/movement. In the second test, rats were habituated to the monitors in the light and then treated with test drug and stimulant (d-amphetamine sulfate or apomorphine HCl). Apomorphine HCl, NPA, and (+)3-PPP antagonized amphetamine-stimulated locomotor behavior (total distance) without antagonizing apomorphine-stimulated behavior, suggesting a presynaptic dopamine autoreceptor agonism. EMD 23448 gave equivocal activity. On the other hand, haloperidol HCl, chlorpromazine HCl, and clozapine decreased both amphetamine- and apomorphine-stimulated behavior, suggesting a postsynaptic dopamine antagonism. 3-PPP and (-)3-PPP showed neither pattern in this test.

Phenothiazine drugs and metabolites: molecular conformation and dopaminergic, alpha adrenergic and muscarinic cholinergic receptor binding

The solid state molecular structures of methoxypromazine and N-monodesmethyl chlorpromazine sulphoxide were determined by X-ray crystallography, as an extension of previous studies on the molecular structures of chlorpromazine sulphoxide and methotrimeprazine sulphoxide. The binding affinities of phenothiazine drugs and metabolites with known crystal structures to dopaminergic, alpha adrenergic and muscarinic cholinergic receptors in rat brain were examined using radio-ligand binding techniques. Comparison of their solid state molecular structures and potencies in neurotransmitter receptor binding reveals that these compounds exist in two different conformations: One, associated with low biological activity, has an angle between the planes of the two aryl rings in the range of 155-160 degrees, and a torsion angle of -80 to -84 degrees around the N(10)-C bond of the side-chain, calculated from the substituted benzene ring. In the other conformation, which is found in the biologically active derivatives, the angle between the planes of the two aryl rings is in the range of 134-145 degrees, and the torsion angle around the N(10)-C bond of the side-chain is in the range of 64-69 degrees or 129-144 degrees. The "active" and "inactive" conformations thus have the side-chain on opposite sides of the ring system.

Comparison of circling induced by unilateral intrastriatal microinjections of haloperidol, clozapine and CCK-8 in rats

The existence of the neuropeptide cholecystokinin (CCK) within a subpopulation of central dopamine (DA) neurons has led to speculations that the peptide may serve as an endogenous modulator of DA functions. To test this possibility, the present study examined the pharmacological action of CCK-8 by comparing its effects on DA-mediated circling behavior with those of a typical (haloperidol; HAL) and an atypical (clozapine; CLZ) dopamine antagonist neuroleptic drug. Rats received unilateral intrastriatal infusions of either sulfated CCK-8 (1, 2, or 8 micrograms), HAL (5 micrograms) or CLZ (5 or 20 micrograms) 15 minutes after systemic injection of d-amphetamine (1 mg/kg). Animals were then placed into rotational chambers where the number and direction of complete 360 degree turns was automatically recorded over a 1 hour session. HAL produced strong and almost exclusive ipsilateral circling while the responses after CLZ and CCK-8 were reliably more variable in rotational direction. More specifically, the results suggest that CLZ is only a weak antagonist of behaviors mediated by striatal DA activation while CCK seems to be devoid of antidopaminergic properties in the striatum.

Behavior performed at onset of drug action and apomorphine stereotypy

This study tests the hypothesis that stereotyped behavior induced by apomorphine reflects strengthening of behavior observed at the onset of drug action. Rats (n = 26) were injected with apomorphine (1.25 mg/kg) while being engaged in copulation. Contrary to the hypothesis, apomorphine did not strengthen ongoing copulation but arrested it. Instead of mating the males became engaged in behavior typically exhibited by rats injected with the drug. It is speculated that stereotyped behavior may be an expression of a drug-induced shift of attention or responsiveness to some particular range of stimuli.

Effects of agonists and antagonists of cholinergic receptors on self-stimulation of the medial prefrontal cortex of the rat

The effects of agonists and antagonists of muscarinic and nicotinic receptors on self-stimulation (SS) of the medial prefrontal cortex (MPC) were investigated. Rats, implanted chronically with monopolar electrodes in the MPC, received subcutaneous injections of nicotine (0.2, 0.4 and 0.8 mg/kg), mecamylamine (2.0, 4.0 and 8.0 mg/kg), pilocarpine (0.5, 1.0, 2.0 and 4.0 mg/kg), scopolamine (0.05, 0.1, 0.2, 0.4 and 0.8 mg/kg) and physostigmine (0.1, 0.2 and 0.4 mg/kg). In order to assess the possible non-specific effects of drugs such as sedation or motor dysfunction, spontaneous locomotor activity (SLA) was used as control. In those groups of rats in which the drugs produced an effect on SS, an operant behaviour for drinking (DB) on an FR-10 schedule was also used as control. Nicotine and mecamylamine had no effect on SS. Both pilocarpine and physostigmine produced a decrease in SS, SLA and DB. Scopolamine, on the contrary, produced a dose-related decrease on SS rate, which was accompanied by a facilitatory effect on SLA and DB. These results suggest that only muscarinic receptors could play a specific role on SS of the MPC.

Deficits in inhibitory avoidance after neurotoxic lesions of the ventral striatum are neurochemically and behaviorally selective

Inhibitory avoidance (step-in type) was investigated in rats subjected to neurochemical lesions of the ventral striatum. The neurotoxins 6-hydroxydopamine or 5,7-dihydroxytryptamine were used to produce selective depletions of either dopamine, norepinephrine or serotonin. Only lesions which decreased the dopamine content of the ventral striatum impaired post-shock step-in behavior. Measurement of footshock reactivity by the Flinch-Jump technique indicated that only serotonin depletion altered reactivity to footshocks. Assessment of open-field locomotor behavior showed that the dopamine-denervated rats were hypoactive (fewer rearings) compared to controls, whereas serotonin-depleted rats were hyperactive. It is concluded that the deficit in inhibitory avoidance behavior following ventral striatal dopamine loss was dissociated from its effect on locomotor activity.

Correlations between aminergic metabolites simultaneously obtained from human CSF and brain

Brain and cerebrospinal fluid (CSF) levels of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) were simultaneously measured in 48 individuals at autopsy. Concentrations of 5-HIAA and HVA in the cerebral cortex were positively correlated with their levels in the CSF for the same individual. Additionally a positive correlation was observed between postmortem CSF levels of 5-HIAA and HVA and a significant concentration gradient for both metabolites was observed in serial fractions of CSF. These findings suggest that determinations of 5-HIAA and HVA in CSF from living individuals may reflect brain metabolite levels as well as the functional activity of these specific neuronal systems.

LSD: the varieties of psychotic experience

The varieties of psychotic LSD experiences are many. A very few may resemble a delirium, some are quite reminiscent of schizophrenia and others have an idiosyncratic quality not seen in the naturally occurring psychoses. The psychotic response to LSD is better understood than transcendent experiences because its neurochemistry and phenomenology have been worked out. Additionally, there is greater familiarity with the endogenous psychoses than the endogenous cosmic experiences. The LSD condition, especially the unsane state, is indeed an experience in search of an explanation. It is doubtful that an animal model for it will be found. It is even possible that not all humans are capable of achieving that state by means of the hallucinogenic drugs. The LSD state remains an area of enormous interest that requires exploration and research.

Effect of chlorpromazine on the localization of cAMP phosphodiesterase

Chlorpromazine (CPZ) at dosages of 10 mg/kg body weight (b.wt.) affected the cytochemical localization of cAMP-dependent phosphodiesterase (cAMP PDE) activity in the synapses of the rat frontal cortex. Postsynaptic cAMP PDE activity was inhibited, and presynaptic activity increased. CPZ also inhibited membrane-bound ATPase activity in the frontal cortex. The activity of Na+-K+-ATPase was significantly (P less than 0.005) inhibited in isolated plasma membranes from the rat frontal cortex. CPZ exposure also affected the cytochemical localization of cations with potassium pyroantimonate. Precipitate, which could be removed with 5 mm EGTA, was decreased in the mitochondria and synaptic vesicles in presynaptic areas after CPZ treatment. The incorporation of 45Ca2+ into slices of the rat frontal cortex was also significantly (P less than 0.001) inhibited by CPZ. This ultrastructural study shows that CPZ may affect biochemical events in an opposite manner in the pre- and post-synaptic areas of some neurons of the frontal cortex.

A genetic analysis of stereotypy in the mouse: dopaminergic plasticity following chronic stress

After repeated stressful experiences, DBA/2 (DBA) mice showed an increase in apomorphine-induced climbing while C57BL/6 (C57) mice showed a clear-cut decrease of this behavior. Genetic analysis involving F1 and F2 hybrids and the backcross populations (F1 X C57; F1 X DBA) indicated complete dominance of the C57 genotype and a significant genotype X environment interaction. These findings are discussed in terms of dopaminergic plasticity and of the heuristic value of this animal model in relation to disturbed behaviors triggered by stressful experiences.

Recurrent dystonic reactions induced by thiethylperazine

Three attacks of acute dystonia occurred in a 19-year-old male following the initiation and discontinuation of thiethylperazine administered rectally in therapeutic doses. The time course of onset of the attacks and the proposed mechanisms by which dystonia develops are discussed.

Effects of iminodibenzyl antipsychotic drugs on cerebral dopamine and alpha-adrenergic receptors

The iminodibenzyl antipsychotic drugs, clocapramine, carpipramine and Y-516 were studied in order to elucidate their mechanisms of action. They all accelerated the accumulation of the dopamine (DA) metabolites, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC), in the striatum and nucleus accumbens of the rat brain. Only Y-516 antagonized in vivo the apomorphine-induced inhibition of DA synthesis as estimated from the accumulation of 3,4-dihydroxyphenylalanine (DOPA) in the decarboxylase-inhibited rat striatum after cessation of nerve impulse flow. All three drugs showed high affinity for DA receptors labelled by [3H]haloperidol and [3H]ADTN in the rat striatum in vitro, with the order of potency Y-516 greater than clocapramine greater than carpipramine. All accelerated the accumulation of the norepinephrine metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), in mouse brain. They showed high affinity for alpha 1-adrenoceptors labelled by [3H]WB 4101 and for alpha 2-adrenoceptors labelled by [3H]clonidine in the rat cerebral cortex in vitro. Although they all had the same level of affinity for the alpha 1-adrenoceptors, Y-516 had less affinity for the alpha 2-adrenoceptors than did clocapramine and carpipramine. The above results indicate that these drugs are potent DA antagonists which block alpha 1- and alpha 2-adrenoceptors in the brain.

Antipsychotic drugs depress acetylcholine release in the Torpedo electric organ, a purely cholinergic system

We used the electric organ of Torpedo, a modified neuromuscular system, to investigate the direct effects of antipsychotic drugs on cholinergic transmission. All the antipsychotic drugs tested inhibited transmission by decreasing the amount of ACh released by nerve impulses. Their potency for this action was as follows: trifluoperazine less than clozapine less than thiethylperazine less than droperidol less than haloperidol less than chlorpromazine = beta-flupentixol less than alpha-flupentixol. Depression of ACh release by antipsychotics was poorly reversible, and was not mediated by dopamine receptors in this system since neither dopamine nor apomorphine had any effect on transmission. Antipsychotics did not act through presynaptic cholinergic receptors since the effect was not antagonized by atropine or quinuclidinyl benzilate. Trifluoperazine had no effect on the total ACh content of the tissue, on the compartmentation of ACh inside and outside synaptic vesicles, or on the rate of ACh turnover or the accumulation of 45Ca observed after repetitive stimulation. We conclude that antipsychotic drugs depress the neurally evoked release of ACh by acting directly on the releasing mechanism.

Antagonism of the amphetamine cue by both classical and atypical antipsychotic drugs

Rats were trained to discriminate the stimulus properties of 1 mg/kg of d-amphetamine sulphate (AMPH) from saline in a two-lever task in which correct responding was reinforced with water under a fixed ratio (FR 32) schedule. Classical antipsychotic drugs from different chemical classes were all able to block the AMPH cue. Doses (mg/kg) inhibiting the cueing effect to 50% (ID50) were 0.035 (haloperidol), 0.04 (spiroperidol), 0.09 (cis(Z)-flupenthixol), 0.12 (trifluperazine), 0.15 (perphenazine), 0.92 (chlorpromazine) and 1.40 (pimozide). The AMPH cue was also antagonized by antipsychotic drugs that are considered atypical due to their relative lack of activity in conventional animal models or inability to produce extrapyramidal symptoms in the clinic. The following ID50 values were obtained: 0.88 (molindone), 1.22 (clozapine), 5.48 (metoclopramide), 15.4 (thioridazine) and 52.8 [-)-sulpiride). In addition, the AMPH cue was blocked by the D-1 selective dopamine (DA) antagonist, SCH 23390 (ID50 = 0.014 mg/kg). The abilities of these drugs to block the AMPH cue were unrelated to the drugs' effect upon the rate of responding. For example, some drugs (e.g. haloperidol, spiroperidol and SCH 23390) blocked the AMPH cue completely without any effect on the response rate. Furthermore, the non-antipsychotic phenothiazine, promethazine (2.5-12.5 mg/kg) failed to affect the AMPH cue although the drug strongly suppressed the response rate. However, the potent DA agonists, apomorphine (0.05-0.33 mg/kg) and lisuride (0.02-0.08 mg/kg), and the DA and norepinephrine agonist, DPI (0.4 and 0.8 mg/kg), did not mimic the AMPH cue or did so only partially. These results suggest that the 1 mg/kg AMPH cue depends on (DA) systems other than those involved in the stereotyped motor behavior commonly produced by high doses of AMPH or DA agonists. Low-dose AMPH discrimination may thus serve as a new model for studying antipsychotic drug action.

Brain dopamine and serotonin receptor sites revealed by digital subtraction autoradiography

Autoradiography combined with image analysis permitted quantitative visualization of dopamine (D2) and serotonin (S2) binding sites in rat brain. Forebrain sections were incubated with tritiated spiroperidol alone or with tritiated spiroperidol plus unlabeled compounds that saturated the D2 or S2 sites. By subtracting the digitized image of an autoradiograph derived from the latter sections from that of the former, the D2 or S2 sites were specifically revealed. The resulting quantitative images demonstrate the differing anatomical distributions of these sites. The D2 site is largely restricted to the striatal complex (caudate-putamen, nucleus accumbens septi, and olfactory tubercle), whereas the S2 site is enriched in layer 5 of motor cortex, the perirhinal and cingulate cortices, and the claustrum.

Ontogeny of striatal unit activity and effects of single or repeated haloperidol administration in rats

Development of striatal unit activity recorded from chloral hydrate anesthetized, neonatal rats was characterized electrophysiologically following acute or repeated haloperidol administration. No spontaneously active single units were detected in 8 day old pups. Spontaneous activity was recorded by 17 days of age, although the number of active cells, firing frequency and the variety of firing patterns were less diverse than those observed in 28 day olds. There were also age related differences in striatal unit responses to haloperidol. A significant increase in activity was induced by acute haloperidol administration only in 28 day old animals. No tolerance to the acute effects was demonstrated. Both 17 and 28 day olds responded to repeated haloperidol injections, followed by a 24 h recess, with an increase in striatal activity. These results may assist our understanding of the effects of human fetal, neonatal and/or adolescent exposure to neuroleptics.

Low HVA and normal 5HIAA CSF levels in drug-free schizophrenic patients compared to healthy volunteers: correlations to symptomatology and family history

Cerebrospinal fluid (CSF) levels of homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5HIAA) were determined in 40 drug-free schizophrenic patients and 21 healthy volunteers by a mass fragmentographic method. Twenty-one of the schizophrenic patients were first admissions who had never received neuroleptics. Significantly, lower levels of HVA but not 5HIAA were found in the patient group, and no difference was found between chronic, previously neuroleptic-treated and never-medicated patients. HVA levels correlated positively with social interest and total positive scores on the Nurses Observation Scale for Inpatient Evaluation (NOSIE-30) and negatively with lassitude and slowness of movements on the Comprehensive Psychopathological Rating Scale (CPRS). Low levels of 5HIAA were correlated to the CPRS items delusions and apparent sadness. There were slightly higher CSF levels of 5HIAA in patients with a family history of schizophrenia, but no such difference was seen for HVA. In both schizophrenic and control subjects CSF levels of HVA and 5HIAA showed a strong intraindividual correlation. The results indicate decreased central nervous system dopaminergic turnover in schizophrenia which seems to be associated with "negative" symptomatology.

Quantitative electrocortical changes in the rat induced by phencyclidine and other stimulants

An automated technique for the continuous analysis of different frequency bands of the electrocorticogram (ECoG) of the rat has been used to quantify the actions of phencyclidine (PCP) and various other stimulant drugs. It has been demonstrated that phencyclidine, etoxadrol and LY154045 produced similar changes in the individual frequency bands whereas amphetamine and apomorphine had different profiles of activity. The phencyclidine-like compounds exhibited extremely strong stimulation of the ECoG with very large increases recorded in high frequency (15-50 Hz) activity and reductions in all other frequency bands. Various compounds have been used in an attempt to antagonise the changes in the ECoG. Chlorpromazine caused a slight shift in the dose-response curves as did chlordiazepoxide when used with phencyclidine. The GABA agonists, THIP and muscimol, had no effect on the stimulation of the ECoG. In contrast another presumed GABA agonist, baclofen, proved to be the most effective agent for blocking the stimulation induced by phencyclidine. The role of the GABAB receptor in the action of phencyclidine is discussed.

Mesolimbic and striatal dopamine receptor supersensitivity: prophylactic and reversal effects of L-prolyl-L-leucyl-glycinamide (PLG)

Functional supersensitivity of mesolimbic and striatal dopamine receptors has been suggested to contribute to the pathogenesis of schizophrenia and tardive dyskinesia. Using the rodent model of chronic administration of the neuroleptic haloperidol, we investigated the possible desensitizing effects of a tripeptide structurally unrelated to dopamine agonists, L-prolyl-L-leucyl-glycinamide (PLG) on mesolimbic and striatal dopaminergic receptor supersensitivity. Administration of PLG either prior to or after chronic haloperidol, inhibited the supersensitivity of dopamine receptors. The results have implications for pharmacological intervention in preventing tardive dyskinesia and relapse psychosis of schizophrenia.

Inhibition of dopaminergic agonist-induced gnawing behavior by neuroleptic drugs in mice

Several neuroleptic drugs cause the Parkinsonian syndrome (PS) in humans; however, this effect is not detectable in rodents. PS-inducing drugs inhibit gnawing or biting behavior induced by apomorphine, amphetamine, DOPA, and thozalinone. The effects of five narcoleptic drugs (chlorpromazine, haloperidol, perphenazine, thioridazine, and trifluoperazine) on this behavior were tested in ICR male mice (10 per dose level). The drugs were given ip 30 min before each of the following inducing agents: DL-DOPA (500 mg/kg, iv), apomorphine (100 mg/kg, ip), amphetamine (12.5 mg/kg, ip), and thozalinone (100 mg/kg, ip). The criterion for blocking effectiveness was the prevention of the biting or gnawing behavior. Prevention indexes (PI) were calculated from the LD50/ED50. Data are consistent with the PS-inducing potencies of these five drugs. Another selective index (SI) of each drug was established by the ED50/ND50 ratio. There is some correlation between PI values and clinical symptoms, but it is not as well defined as that between SI values and clinical symptoms. Data from the thozalinone test (SI) appear to provide the best prediction for the PS-inducing potencies of the drugs tested. Thus, this technique appears to be suitable for use as an animal model in preclinical toxicity studies.

Haloperidol plasma levels and clinical response in paranoid schizophrenics

The relationship between haloperidol plasma levels, plasma prolactin, and therapeutic efficacy was evaluated in 20 paranoïd schizophrenics in a fixed-dose study for 6 weeks. We found a significant intrapatient cross-correlation of therapeutic efficacy, as measured by decrease in MSS and BPRS rating scales and time-dependent haloperidol and prolactin changes, which were tested at weekly intervals. However, no significant curvilinear relationship was present between steady-state haloperidol plasma levels and MSS and BPRS improvement scores. Our data do not furnish clear-cut evidence in favor of the existence of a therapeutic window for haloperidol plasma levels in paranoïd schizophrenia.

The effects of SCH 23390, YM 09151-2, (+)- and (-)-3-PPP and some classical neuroleptics on D-1 and D-2 receptors in rat neostriatum in vitro

The actions in vitro of SCH 23390, YM 09151-2 and both enantiomers of 3-PPP on D-1 and D-2 dopamine receptors were investigated in superfused rat neostriatal slices. For comparison the following neuroleptics of different chemical classes were incorporated in our investigations: (+)-bulbocapnine, clozapine, chlorpromazine, cis-flupenthixol, (-)-sulpiride and haloperidol. The increase in the efflux of cyclic AMP was used as a measure for D-1 receptor stimulation. The decrease in the K+-evoked release of [3H]acetylcholine was used as measure of D-2 receptor stimulation. None of the drugs stimulated the D-1 receptor. Only (+)-3-PPP stimulated the D-2 receptor. All other drugs, including (-)-3-PPP, behaved as antagonists on the D-2 receptor, YM 09151-2 being the most potent. SCH 23390 was the most potent antagonist on the D-1 receptor. Haloperidol, cis-flupenthixol and (+)-bulbocapnine showed an appreciable D-1 receptor blocking potency in our model, whereas the other drugs were inactive. We found SCH 23390 to be the most D-1 selective antagonist although the drug still displayed considerable potency on the D-2 receptor. YM 09151-2 was the most D-2 selective antagonist.

Atypical neuroleptics clozapine and thioridazine enhance amphetamine-induced stereotypy

The effects of the atypical neuroleptics clozapine and thioridazine and the typical neuroleptic pimozide on amphetamine-induced behavior were examined. Pimozide, as expected, blocked both amphetamine-induced locomotion and stereotypy. Thioridazine and clozapine antagonized the increases in locomotion produced by amphetamine, but produced increases in amphetamine-induced stereotypy and lowered the threshold dose for stereotypy. It is suggested that the increased stereotypy might partly account for the decreased locomotion, and that this might be a primary effect of these atypical neuroleptics. The data would also suggest that the use of amphetamine-induced stereotypy as a model for psychosis is inappropriate, as clozapine and thioridazine, which enhance stereotypy, are antipsychotic.

ERPs and psychopathology. II. Biological issues

We have briefly covered important issues and considerations in four topic areas likely to be of use to the ERP researcher who is also interested in biological psychiatry. We cannot ignore diagnosis because of its basic role in the field of psychiatry. Although there are reliability problems, especially in the field of psychiatric diagnosis, ERPs may help in the painstaking task of validating diagnosis based on behavioral observation. In addition, the ERP researcher can use diagnosis to obtain potentially more homogeneous samples of patients so as to reduce between-subject error variance in studies. We have considered research areas like PET scan and CT scan which provide data of more anatomical precision than ERPs for deep neurological sites. While the potential may be there, it is essentially unrealized as yet. Finally, neurochemistry and psychopharmacology seem to be the areas most likely to bear fruit in the immediate future. If this potential is to be realized, it is necessary to formulate new questions and a new methodology to handle these questions. An important question, for example, is whether a biological profile is a more useful criterion than a behavioral profile for predicting response to pharmacological intervention. In biological psychiatry, this question is a human suffering issue of considerable importance.

CCK-33 antagonizes apomorphine-induced growth hormone secretion and increases basal prolactin levels in man

Cholecystokinin (CCK-33) (225 Ivy Dog Units intravenously) had no effect on basal growth hormone (GH) secretion but antagonized the GH response to the dopamine receptor agonist, apomorphine HCl (0.5 mg sc) (N = 7), and induced a transient increase in basal prolactin (PRL) secretion (N = 8) in normal men. These findings are similar to those described with neuroleptics and are compatible with an inhibitory effect of CCK-33, or fragments, on dopamine function in man, at least in the hypothalamic-pituitary axis. However, an inhibitory effect of CCK-33 on the release of GH and a stress-induced increase in PRL secretion cannot be excluded.

Neuroleptic-induced dopamine hyposensitivity

In contrast to dopaminergic hypersensitivity induced by most neuroleptic drugs including fluphenazine, thioridazine induced hyposensitivity to subsequent apomorphine stereotypy in rats. The difference between thioridazine and fluphenazine may relate in part to anticholinergic properties of thioridazine, but appears to involve additional mechanisms. Differences in dopaminergic sensitization may be important to the management and prevention of tardive dyskinesia an iatrogenic disorder associated with chronic exposure to neuroleptics.

Similarity between (+)-amphetamine and amfonelic acid

Rats, trained to discriminate the CNS stimulant (+)-amphetamine (1.0 mg/kg) from saline in a two-lever drug administration task, were challenged with various doses of the structurally dissimilar CNS stimulant amfonelic acid. Amfonelic acid was found to substitute for the amphetamine stimulus and was found to be 1.5 times more potent than amphetamine.

Emergency psychopharmacology

A review of the literature pertinent to the emergency use of psychotropic agents is presented. Four general principles (underlying organicity, target symptoms, route of administration, and side effect profiles) governing the choice of psychotropic agent are discussed. Pharmacologic management approaches to commonly encountered behavioral emergencies, including drug-related disorders, assaultive patients, suicidal patients, agitated patients, and stuporous/withdrawn patients, are outlined.

Critical issues in assessing the behavioral effects of amphetamine

Amphetamine induces a behavioral syndrome in mammals that includes a variety of repetitive behaviors. An integral component of this syndrome in humans is the presence of a thought disturbance not unlike that manifest in idiopathic paranoid schizophrenia. The consistent pattern of behavioral changes produced by amphetamine across species, when considered in light of the psychosis it elicits in humans, has suggested to many that these drug-induced changes in animals may provide a model of the endogenous psychosis in humans. Amphetamine-induced changes in open-field behavior in the rat have been the most widely studied in attempts to formulate a model for investigating the neurobiological mechanisms underlying amphetamine psychosis and paranoid schizophrenia in humans and for testing the therapeutic efficacy of new antipsychotic drugs. The procedures used to assess the behavioral response to amphetamine, however, typically include rating scales or automated recordings that by their very nature ignore those components of the behavioral response that may be most critical for developing a viable animal model of the naturally occurring psychosis. Further, open-field behavior is often recorded during arbitrarily selected intervals without consideration for the multiphasic nature of the entire amphetamine response. We discuss how incomplete descriptive analyses of the amphetamine behavioral response in rats has led to confusion in the literature and describe behavioral research that is paradigmatic of the work we believe is most likely to eventuate in significant progress in the field.

Action of putative dopamine receptor agonists, TL-99, 3-PPP and RDS-127 on substantia nigra neurons

The inhibitory actions of 3 putative dopamine receptor agonists on the firing of neurons in slices of rat substantia nigra in vitro was examined. The EPMR values for 3-PPP, RDS-127 and TL-99 were 1.11, 2.66 X 10(-3) and 2.4 X 10(-4) respectively. All 3 agonist effects were antagonized by 1 microM sulpiride.

Prophylactic effect of neuroleptics in symptom-free schizophrenics: a comparative dose-response study of haloperidol and propericiazine

Remitted schizophrenic outpatients were treated in order to prevent relapse with three doses of haloperidol or propericiazine for 1 year in a double-blind controlled study employing a randomized design. The drug's ability to prevent relapse was evaluated by counting the number of symptom-free days for each patient before any sign of relapse or over-dose appeared. Patients were randomly assigned to the following drugs orally administered once per day at night: placebo; haloperidol 1 mg, 3 mg, and 6 mg; propericiazine 10 mg, 30 mg, and 60 mg. Serum prolactin levels in each patient were estimated by radioimmunoassay. All patients treated with placebo relapsed within 1 year and the relapse rate with placebo was significantly higher than with any dose of the two neuroleptics. Haloperidol increased the number of symptom-free days in a dose-dependent manner. Propericiazine at 10 mg and 30 mg also increased the number of symptom-free days dose-dependently but at 60 mg, the number decreased. It appears that propericiazine shows an inverted U-shaped dose-response curve. Prolactin levels were elevated dose-dependently by both drugs but failed to show a significant correlation with the number of symptom-free days. The present results indicate that haloperidol is superior to propericiazine from the viewpoint of the wider "therapeutic window" in maintenance treatment and antidopaminergic properties of neuroleptics, wherein it is important to prevent relapse even in remitted schizophrenics.

Phencyclidine-induced locomotor activity in the rat is blocked by 6-hydroxydopamine lesion of the nucleus accumbens: comparisons to other psychomotor stimulants

The present study was primarily designed to explore the relationship between phencyclidine(PCP)-induced hyperactivity and the mesolimbic dopamine (DA) system. In addition, the motor-activating and behavioral effects of amphetamine (1.5 mg/kg), SKF-10,047 (25.0 mg/kg), scopolamine (1.0 mg/kg), and caffeine (10.0 mg/kg) were also measured and compared to PCP action. While all compounds produced a moderate to large degree of hyperactivity with varying time courses for effect, gross behavioral observations indicated a greater similarity between PCP and SKF-10,047 than between any of the other drugs. Following bilateral 6-hydroxydopamine lesions of the nucleus accumbens the robust locomotor-stimulating action of 5 mg/kg PCP was significantly reduced. Such lesions also successfully prevented amphetamine- and SKF-10,047-induced hyperactivity, but not the behavioral activation produced by scopolamine or caffeine. These results suggest that PCP and SKF-10,047, like amphetamine, elicit locomotor activity through presynaptic DA mechanisms within the mesolimbic system.

Dopamine and non-dopamine psychoses

The time course of antipsychotic response following the initiation of an antipsychotic drug and functional dopamine receptor sensitivity were explored in a cohort of recently admitted psychotic (mood-incongruent) patients. The distribution of the latencies of antipsychotic response suggested at least two populations. Rapid responders (RRs) had 60% reduction of baseline psychotic symptoms by a mean of 5.5 days of drug treatment. Delayed/nonresponders required 2-7 weeks for a similar reduction of psychotic symptoms. The sensitivity of postsynaptic dopamine receptors was explored using a neuroendocrine probe: growth hormone response to the dopamine agonist, apomorphine (AP). RRs had an exaggerated growth hormone response to AP in comparison to delayed/nonresponders (P less than 0.05). Exaggerated sensitivity of postsynaptic dopamine receptors and rapid antipsychotic response following dopamine receptor blockade in RRs suggest a true functional dopamine hypersensitivity disorder in the RR group. In contrast, lower postsynaptic receptor sensitivity (as reflected by lower growth hormone response to AP) and failure of early response following dopamine receptor blockade focus attention away from dopamine hyperactivity as a relevant etiologic mechanism in delayed/nonresponders. Response rates to neuroleptic drugs and neuroendocrine probes of receptor sensitivity may separate two or more etiologically distinct diseases with schizophrenic-like symptoms.

Can neuroleptics influence the function of the brain hemispheres asymmetrically?

A long-term intracarotid tube was implanted in 32 rats. Intracarotid injection of 4 different neuroleptics (haloperidol, cis- and trans-flupenthixol, clopenthixol and reserpine) elicited a typical posture with abduction of the limbs on one side and and adduction on the other. Only the neuroleptically-active cis-isomers of flupenthixol and clopenthixol provoked this dystonic reaction. The posture spontaneously vanished after 24 hr and could be antagonized with the anticholinergic biperiden. Sham injections of Ringer's solution and isotonic glucose proved to be behaviourally inert. These results indicate an asymmetric distribution of the drugs in this experimental procedure. Their implications concerning drug-induced and spontaneous dystonias as well as psythopathology are discussed.

Continuous amphetamine intoxication: an animal model of the acute psychotic episode

When amphetamines are administered to humans every few hours for several days, either during the 'speed runs' of addicts or in controlled laboratory settings, the psychosis which reliably results is similar to paranoid schizophrenia in a number of important aspects. This unique regimen of drug intake, which involves the continuous presence of stimulants over a prolonged period of time, can be simulated in animals using subcutaneously implanted slow-release silicone pellets containing d-amphetamine base. Monkeys and rats implanted with these pellets develop stages of behavioural alterations which are somewhat similar in sequence to those observed in humans who have received frequent doses of amphetamine. An initial period of hyperactivity and exploratory behaviour is followed by the gradual development of motor stereotypies which become virtually incessant. A period of relative inactivity then appears which is followed, at 4-5 days after pellet implantation, by a late stage. This final stage is characterized by 'wet-dog' shakes, parasitotic-like grooming episodes, and a variety of other forms of hallucinatory-like behaviour. At about the same time there are distinctive and partially irreversible alterations in dopaminergic innervations of the caudate nucleus, but not in mesolimbic dopamine innervation of the nucleus accumbens or in several other neurotransmitter systems. Continuous amphetamine administration may reproduce some aspects of the prolonged excitation which accompanies an acute psychotic episode and may be a fruitful model for the clarification of the dopamine theory of schizophrenia.