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1 The aggregation response of platelets induced by 5-HT was greatly increased in psychiatric patients receiving chlorpromazine therapy when compared with normal volunteers and psychiatric patients not receiving chlorpromazine. 2 Platelet aggregation responses to ADP were normal during chlorpromazine therapy, but 5-HT induced aggregation was increased in rate and the typical transient reversible response was converted to an irreversible response in all subjects. This was usually indistinguishable from the ADP response. 3 When chlorpromazine therapy was stopped, plasma concentrations of chlorpromazine, monodesmethylchlorpromazine and chlorpromazine sulphoxide fell rapidly within one week, whereas 5-HT induced platelet aggregation responses became normal after three weeks. The enhanced responses returned when chlorpromazine therapy was re-instituted. 4 It is possible that platelet aggregation responses to 5-HT in vitro could prove to be a useful index of the pharmacological effect of chlorpromazine in vivo. [ABSTRACT FROM AUTHOR]

1 Previous work showed that platelets from patients receiving chlorpromazine (CPZ) have an enhanced aggregation response to 5-HT. This was caused by an action of CPZ on the platelets, a factor borne by the plasma, or both. 2 Therefore we studied 5-HT induced aggregation of platelets from CPZ treated patients resuspended in normal plasma and from normal subjects resuspended in CPZ plasma. 3 Aggregation responses of normal platelets to 5-HT were not enhanced by resuspension either in normal plasma or in CPZ plasma. In addition the enhanced responses of platelets from CPZ treated patients did not revert to normal after resuspension in normal plasma. 4 It is concluded that the enhanced aggregation response to 5-HT seen after CPZ treatment is due to a change in the properties of the platelets rather than a factor in the plasma. [ABSTRACT FROM AUTHOR]

The isolated human basilar artery suspended in Kreb's solution contracts to 5-hydroxy-tryptamine, noradrenaline, and histamine, which stimulate specific receptors. Normal human serum contains an unidentified contractile substance, and erythrocytes relax the artery. Serum and erythrocytes potentiate 5-HT contractions. This preparation is suitable for studying vasoactive substances released during vasospasm after subarachnoid haemorrhage.

The responses of baboon cerebral and extracerebral arteries to prostaglandin endoperoxide (PGH2) and prostacyclin (PGI2) were investigated on isolated arteries and in vivo by serial angiography. Both PGH2 and PGI2 could produce dose-dependent contraction or relaxation of isolated arteries. PGH2 induced relaxation was indicative of prostacyclin synthetase activity, the enzyme which converts PGH2 to PGI2. In isolated arteries tested one to four hours post mortem only the vertebral artery showed prostacyclin synthetase activity. Thus PGH2 induced contraction of cerebral arteries may be indicative of a physiological function. Vasomotor tone may in part be the result of a balance between PGH2 constriction and PGI2 dilatation. In vivo PGI2 infusion caused pronounced and prolonged dilatation of cerebral arteries, which lasted longer than the cardiovascular changes. As PGI2 is the most potent cerebral vasodilator drug tested, it may be of clinical use in the treatment of cerebral vasospasm.

1 Blood platelets from normal human subjects were isolated and aggregated in vitro with adenosine diphosphate (ADP) or 5-hydroxytryptamine (5-HT). 2 The effects of chlorpromazine and 7 major metabolites upon 5-HT-induced aggregation were investigated. 3 All the phenothiazines inhibited 5-HT-induced aggregation when added to platelet rich plasma 3 min prior to 5-HT. 4 There were no qualitative differences in the inhibitory effects, but inhibitory potency varied over a wide range. The decreasing order of potency was monodesmethylchlorpromazine, chlorpromazine, 7-hydroxychlorpromazine, didesmethylchlorpromazine, 3,7 -dimethoxy-chlorpromazine, didesmethylchlorpromazine sulphoxide, chlorpromazine sulphoxide, chlorpromazine nitroxide.

The relationship between clinical condition and vasoconstrictor factors in cerebrospinal fluid was studied in 19 patients for up to six weeks after subarachnoid haemorrhage. Vasoconstrictor activity was assayed biologically. Sixteen of 19 patients improved as vasoconstrictor activity declined; this pattern was not significantly influenced by surgery. Serial angiography was performed on three patients and a qualitative relationship was shown between arterial dilatation, clinical improvement, and reduced pharmacological activity.

Rupture of human cerebral arterial aneurysms is followed by prolonged cerebral arterial constriction; there is evidence that cerebrospinal fluid (CSF) from such patients contains vasoconstrictor substances which may cause the arterial constriction. The aim of this study was to develop a small animal model for investigating the effects of such CSF on the calibre of cerebral vessels in situ. Carotid angiography of the cerebral arteries of the rat visualizes the internal carotid, middle cerebral, anterior cerebral and stapedial arteries plus the vertebrobasilar system. Prostacyclin was injected during carotid catheterisation to prevent spontaneous and random occlusion of these cerebral arteries; in the presence of prostacyclin there was no arterial occlusion for up to 5 h. The resolution achieved by the angiographic technique, which magnified the cerebral circulations 2.9 times, was sufficient to measure the diameter of the internal carotid and stapedial arteries of the rat. Intracarotid infusion of 1.0 ml CSF collected from patients with ruptured cerebral arterial aneurysms caused a rapidly developing contraction of cerebral arteries lasting up to 5 h. Thus, we consider that the rat may also be used as a model for investigating the aetiology of human cerebral arterial constriction after aneurysmal rupture.

Endogenous platelet taurine and uptake of radioactively labelled taurine by platelets was measured in normal, non-mongoloid and mentally retarded mongoloid trisomy 21 subjects. Endogenous taurine was normal in all groups, while taurine transport kinetic experiments showed normal Km but reduced Vmax in mongoloid trisomy 21 and mentally retarded patients. The latter difference may be due to decreased metabolism following decreased enzyme protein synthesis.

Platelet monoamine oxidase activity was measured in 9 autistic subjects and 9 controls. There were no significant differences in the rates of metabolism of 5-hydroxytryptamine, dopamine or tyramine between the two groups, although the rate of metabolism of tyramine was more rapid than 5-hydroxytryptamine or dopamine within each group. It is concluded that the data presented do not support the view that measurement of platelet monoamine oxidase can be used as a biochemical index to aid in the clinical diagnosis of infantile autism.

This simplified determination of serotonin in human plasma involves "high-performance" liquid chromatography with electrochemical detection. Deproteinated samples of platelet-poor plasma are injected directly into the chromatograph without preliminary chromatographic purification. The limit of quantitative detection of serotonin in plasma is 5 nmol/L (equivalent to 250 fmol injected). Intra- and inter-assay CVs ranged from 5.6% to 7.7% and 3.5% to 14.9%, respectively, for concentrations of serotonin from 0.02 to 10.0 mumol/L. Results agreed well with those by spectrofluorometry, both for plasma standards (r = 0.985, range 100 nmol/L to 100 mumol/L) and for pathological samples obtained from four carcinoid syndrome patients (r = 0.964). The method is also applicable to the concurrent measurement of 5-hydroxytryptophan and 5-hydroxyindoleacetic acid.

Cerebrospinal fluid (CSF) was collected preoperatively (by lumbar puncture) or perioperatively (by lumbar or ventricular drain) from 32 patients with subarachnoid hemorrhage (SAH) from ruptured intracranial aneurysms. Samples were also obtained from six control patients without evidence of subarachnoid blood. Smooth-muscle constrictor activity in the CSF was measured by bioassay using the isolated rat stomach fundus preparation. Concentrations of unidentified smooth-muscle constrictor substances were considerably greater in CSF from a group of seven patients with evidence of severe angiographic vasospasm and/or delayed ischemic deficits who died (73.8 +/- 39.7 nmol/liter prostaglandin E2 (PGE2) equivalents), as compared to 25 other SAH patients who survived (6.5 +/- 1.4 nmol/liter PGE2 equivalents), and six control patients (1.17 +/- 0.34 nmol/liter PGE2 equivalents). The data suggest that there is a relationship between smooth-muscle constrictor substances in the CSF after SAH and both the degree of angiographic vasospasm and the outcome. It is possible that this relationship might be exploited clinically.

Vasoconstrictor activity was examined in serial samples of cerebrospinal fluid (CSF) obtained from 10 patients undergoing aneurysm clipping within 48 hours after subarachnoid hemorrhage (SAH). There was no close relationship between vasoconstrictor activity in postoperative CSF samples and the patient's clinical condition or angiographic vasospasm. The identity of the vasoconstrictor substance(s) in CSF was not established, but serotonin, histamine, norepinephrine, epinephrine, acetylcholine, or angiotensin II were eliminated as prime vasoconstrictor agents inducing cerebral vasospasm. Differences in the temporal profile of the responses of isolated tissues to CSF from patients with early and late surgery suggested that differing substances were involved in the production of spasm. A correlation between CSF potassium concentrations and vasoactive substances was found, but potassium could not account for vasoconstrictor activity of CSF. A log:linear correlation between total vasoconstrictor activity and total CSF collected could not be explained. Also, because of possible differences in the identity of vasoactive substances in CSF in this study compared to earlier studies, clinical comparisons based on apparent differences in pharmacological potency of CSF were not warranted. Nevertheless, removal of subarachnoid blood by cisternal rinsing seemed to be a useful surgical adjunct.

1 The binding of [3H]-5-hydroxytryptamine ([3H]-5-HT), [3H]-haloperidol and [3H]-dopamine to human blood platelets was investigated and the effects of unlabelled haloperidol on [3H]-5-HT binding and (+)- and (-)-butaclamol on [3H]-haloperidol were studied. 2 Scatchard analysis did not show any specific binding of [3H]-haloperidol or [3H]-dopamine to platelets, but two binding sites were identified for binding of [3H]-5-HT. 3 Unlabelled haloperidol reduced the binding of 5-HT in concentrations comparable to those inhibigint 5-HT-induced platelet aggregation; (+)- and (-)-butaclamol did not affect the binding of [3H]-haloperidol. 4 It is concluded that haloperidol binding represents saturation of the platelet membrane, and that the platelet is not a suitable model for investigation of dopamine-drug interactions.

1 Because normal human blood platelets contain higher concentrations of taurine than any other amino acid, and have a platelet: plasma concentration gradient exceeding 400: 1, we isolated the cells in vitro and incubated them with radioactively labelled taurine in order to investigate the existence of a metabolically-dependent accumulation process.2 Platelets incubated with taurine (1 to 100 nmol/ml) in autologous plasma or Krebs solution accumulated [(14)C]-taurine against the concentration gradient.3 The transport process was saturable at high concentrations, showed a requirement for sodium ions, and was temperature-dependent.4 The kinetics of transport fulfilled the criteria of Michaelis & Menten for saturable enzyme/substrate interactions, but the kinetic constants were influenced by the incubation medium.5 The metabolic inhibitors 2,4-dinitrophenol and iodoacetic acid in combination inhibited taurine transport in Krebs solution, but stimulated transport in autologous plasma. The latter result suggested the involvement of a sodium-dependent ATPase in taurine transport.6 We conclude that platelets actively transport taurine in vitro under experimental conditions closely resembling those likely to occur in vivo, and that this taurine transport process may be involved in the maintenance of the platelet: plasma concentration gradient.

1 Blood platelets from normal human volunteers were isolated and aggregated in vitro with 5-hydroxytryptamine (5-HT), noradrenaline (NA), dopamine and N-dimethyldopamine (DMDA). 2 The effects of 5-HT antagonists, alpha- and beta-adrenoceptor blocking agents, butyrophenones and chlorpromazine upon aggregation induced by the four amines were investigated. 3 Only the the 5-HT antagonists, chlorpromazine and spiroperidol were potent inhibitors of 5-HT-induced aggregation, and only phentolamine was a potent inhibitor of the catecholamine-induced aggregation. 4 Evidence was obtained for two populations of receptors, one for 5-HT and one for the three catecholamines.

Injection of tranylcypromine and L-tryptophan results in rats displaying behavioural changes including hyperactivity, probably due to stimulation of post-synaptic 5-hydroxytryptamine (5-HT) receptors. Increased locomotor activity of a different type is elicited by injection of tranylcypromine and L-dopa, a procedure which increased dopaminergic function in the brain. It has now been demonstrated that the neuroleptic drugs, chlorpromazine, alpha-flupenthixol, haloperidol and spiroperidol block both syndromes. The inhibition produced by these drugs on 5-HT-induced hyperactivity is probably because a dopaminergic system is involved in the behavioural expression of the 5-HT induced hyperactivity. The structurally related drugs with no neuroleptic activity (ethopropazine, promethazine and beta-flupenthixol)are without effect on thses hyperactivity syndromes. Also ineffective were the neuroleptics pimozide and clozapine. Striatal dopamine sensitive adenylate cyclase activity in vitro was inhibited by the administration of chlorpromazine (100 mg/kg) in vivo. Rats treated for 4 or more days with chlorpromazine, alpha-flupenthixol, spiroperidol and haloperidol subsequently showed enhanced locomotor activity in response to tranylcypromine and L-Dopa. Administration of those drugs which did not block hyperactivity acutely did not result in enhancement. Only chlorpromazine, when given for 4 days, enhanced the hyperactivity response following tranylcypromine and L-tryptophan, probably because the drug also blocks 5-HT receptors. In rats displaying enhanced behavioural responses no evidence was found for enhanced sensitivity of striatal adenylate cyclase to dopamine.

Cerebrospinal fluid from six cases of acute spinal trauma collected 0--6 days after injury was examined for vasoconstrictor activity using both human isolated cerebral arteries and animal tissues. The cerebrospinal fluid of four out of six patients was vasoactive. The identities of the vasoconstrictor substances were not established, but experiments with pharmacological antagonists showed that arterial contractions were not due to serotonin, histamine, noradrenaline, acetylcholine or angiotensin II, substances which are known potent spastic agents on cerebral arteries. Our findings would explain by the mechanism of arterial spasm, principally in the anterior spinal artery, the neuropathological appearance of central haemorrhagic necrosis in spinal cord injury. The infarction of the core of the spinal cord could be caused by vasoconstrictor substances, reported here, in the cerebrospinal fluid after spinal injury. If the identities of the substances could be established, drug therapy to prevent or relieve the spasm would be possible.

Platelet shape change responses to 5-hydroxytryptamine were examined in 11 normal subjects and in 78 patients with psychiatric disorders receiving one or more of the following classes of drug: phenothiazine, thioxanthine, butyrophenone, tricyclic antidepressant, benzodiazepine or lithium. Approximately 37% of patients received a single drug, the remainder up to 4 other compounds in addition to the main drug. Platelet shape change induced by 5-hydroxytryptamine (0.25, 2.5 or 25 nmol/ml) was significantly inhibited in patients treated with phenothiazines, thioxanthines and butyrophenones (haloperidol). Tricyclic antidepressants, lithium and benzodiazepines had no effect on 5-hydroxytryptamine-induced shape change. In contrast, a combination of lithium plus chlorpromazine significantly enhanced platelet shape change. Potentiation of noradrenaline-induced aggregation was approximately 50% in normal subjects. This degree of potentiation was not altered in the drug-treated patients although there were quantitative reductions in magnitude of response. Platelet shape change in addition to platelet aggregation may be used as a pharmacological tool to investigate the aetiology of psychiatric disorders and, perhaps eventually, to monitor the clinical efficacy of drug therapy.

In nine baboons following intracisternal injection of a suspension of their own washed platelets, biphasic spasm was demonstrated by vertebral angiography. Constriction of the intra-arachnoid portion of the vertebral artery and the basilar artery was severe 10 minutes after the platelet injection, had begun to relax after one hour, but had returned on day 2 or 3. It persisted for about 8 days. The animals showed clinical evidence of neurological damage. At autopsy the vertebral and basilar arteries showed stripping of the endothelium, with adherent platelets, protein and other cells. There was blockage of some small branches. The brains showed ischaemic changes. The clinical phenomenon of spasm after subarachnoid haemorrhage was thus fairly closely modelled by the injection of platelets alone. There was some evidence that 5HT was probably not responsible for the delayed phase of spasm. Some suggestions are made about the mechanism.

The effects of leukotriene D4 (LTD4), a component of the slow reacting substance of anaphylaxis (SRS-A), and the putative SRS-A antagonist FPL 55712 were studied on cerebral arteries in vivo and in vitro. Intracarotid injection of LTD4 (1-15 nmols/kg) into the cerebral vasculature of the anaesthetised rat constricted internal and external carotid, facio-lingual and stapedial arteries for up to 40 minutes. LTD4 at 3 nmol/kg caused a slight fall in heart rate, and at 6 and 12 nmol/kg, an increase in diastolic (but not systolic) blood pressure was observed. In some experiments, constriction was followed by dilatation (possibly due to enhanced prostacyclin synthesis). FPL 55712 (0.3 to 30 nmols/kg) injected in the same manner caused both constriction and dilatation of rat cerebral arteries. In vitro experiments were performed on isolated human intracranial arteries (basilar, vertebral and Circle of Willis) obtained at autopsy, and on the isolated rat stomach fundus. LTD4 (2 x 10(-9) to 2 x 10(-7) M) caused sustained contractions of isolated human intracranial arteries. FPL 55712 (up to 4 x 10(-7) M) failed to antagonise the vasoconstrictor effects of LTD4, and higher concentrations (8 x 10(-6) to 8 x 10(-5) M) directly relaxed cerebral arteries. In contrast, FPL 55712 (2 x 10(-8) M) was a competitive antagonist of the contractile effects of LTD4 on the isolated rat fundus. This data suggests that the cerebral arterial leukotriene receptor differs from the peripheral smooth muscle receptor typified by the guinea-pig ileum and rat fundus preparations. Furthermore, leukotrienes may be involved in pathological vasoconstriction of various vascular beds after immunological reaction and trauma.

1 The pharmacological similarity between human basilar artery and a number of isolated tissues (rat colon, anococcygeus, stomach fundus and aorta and guinea-pig ileum and colon) has been assessed during investigations of the aetiology of cerebral arterial spasm. 2 The responses of each of the six tissues to human normal and abnormal cerebrospinal fluid (CSF) and to human serum were compared with those of the human isolated basilar artery. 3 These studies revealed the presence of a vasodilator factor in CSF from subarachnoid haemorrhage patients and several tissues may be of use for further work in identifying the vasoactive substances in CSF. 4 No tissue displayed exactly the same spectrum of biological reactivity as the human basilar artery. The rat stomach fundus showed the closest similarity and was further studied for similarities in drug-induced responses. 5 The rat stomach fundus, like the human basilar artery, was contracted by 5-hydroxytryptamine, prostaglandin F2alpha and histamine and relaxed by dopamine. However, noradrenaline relaxed the fundus but contracted the basilar artery.

The effects of the alpha- and beta-isomers of flupenthixol on 5-hydroxytryptamine (5-HT)-induced platelet aggregation and on 5-HT and dopamine uptake were investigated. Alpha-Flupenthixol was 185 times more potent than the beta-isomer as an inhibitor of platelet aggregation. In contrast both isomers were equipotent as inhibitors of uptake of 5-HT and dopamine. The data suggest that 5-HT-induced aggregation and uptake are separate processes.

Defects in brain neurotransmitter function are believed to be involved in the aetiology of mood disorders, and model systems are based on this concept. Abnormalities in synthesis, storage, release, reuptake or catabolism of monamines, GABA, glycine, taurine, peptides and purines may occur. There may also be an endogenous psychotogen--an aberrant metabolite of a transmitter. Models are divided into two groups. 1. Human. Brain, CSF, blood cells (platelets, erythrocytes), plasma and urine have been analysed for neurotransmitters or metabolites. Particular emphasis has been given to serotonin (5-HT) and the catecholamines, dopamine and noradrenaline. 2. Animal. Human mood disorders may be stimulated by drug-induced behavioural changes in animals (hyperactivity, stereotyped behaviour sedation). The above biochemical parameters relating to neuronal function can then be assessed. Brain neuronal pathways can be stimulated in animals with monoamine precursors and MAO inhibitor drugs. This drug-induced hyperactivity can be used to "evaluate" therapeutic techniques such as electroconvulsive therapy (ECT). Model analogues of mood disorder have limited use until human disease aetiology is known, currently the best use of models may be for demonstration and evaluation of particular similarities between human mood disorders and drug-induced alterations of animal behavioural patterns.

Peri-aneurysmal CSF was obtained at operation from 13 patients with subarachnoid haemorrhage from ruptured intracranial aneurysms. The 5-hydroxytryptamine antagonist ketanserin inhibited contractions of isolated human intracranial arteries, elicited by this CSF. The presence of 5-HT in CSF was confirmed by high performance liquid chromatography. The use of ketanserin in the therapy of postoperative cerebral vasospasm is discussed.

Oxyhemoglobin was injected intracisternally into three baboons, and methemoglobin into one baboon, in an attempt to mimic the prolonged cerebral arterial spasm sometimes seen after subarachnoid hemorrhage due to aneurysm rupture. Cerebral angiography was performed for up to 7 days after injection of hemoglobin, and the degree of vasospasm was estimated from the angiograms. Oxyhemoglobin caused slight arterial narrowing, which lasted for 3 days. Methemoglobin had no significant effects. Motor neurological deficits and histopathological signs, characteristic of prolonged cerebral vasospasm, were not observed. It was concluded that hemoglobin alone is not capable of causing the cerebral vasospasm syndrome in these experimental animals.

Cerebrospinal fluid from patients with subarachnoid haemorrhage and cerebral arterial spasm contracted the isolated basilar artery and potentiated contractions produced by 5-hydroxytryptamine, noradrenaline, and six prostaglandins. The unidentified substance in cerebrospinal fluid probably plays a role in the aetiology of cerebral arterial spasm.

Platelet aggregation responses to 5-HT, dopamine, N-dimethyl dopamine and adenosine diphosphate were compared in normal subjects and patients treated with chlorpromazine (CPZ) for longer than 6 months. We confirmed our previous finding that 5-HT induced aggregation is enhanced in CPZ treated patients. Increased aggregation responses were also observed with dopamine and N-dimethyl dopamine. Quantitative comparisons of aggregation rates and total changes in optical density of platelet rich plasma relative to adenosine diphosphate showed significant increases with 5-HT, dopamine and N-dimethyl dopamine. Implication of dopaminergic mechanisms in the central effects of phenothiazines suggests that changes in dopamine induced aggregation responses may be useful in attempting correlations of clinical and pharmacological effects.