An unusual cluster of tardive dyskinesia in schizophrenia: association with cognitive dysfunction and negative symptoms

Factors associated with the emergence or nonemergence of involuntary movements (tardive dyskinesia) during long-term neuroleptic treatment were investigated in an atypical, isolated population of 31 schizophrenic inpatients with an unusually high prevalence of this syndrome. Patients with involuntary movements could not be distinguished from those without such movements by general characteristics or conventional indices of neuroleptic or anticholinergic treatment. However, they were more likely to show either marked cognitive dysfunction or muteness. These findings support the proposal that, at least in schizophrenia, subtle organic changes may contribute to vulnerability to the emergence of involuntary movements.

Stereotyped behaviour in response to the selective D-2 dopamine receptor agonist RU 24213 is enhanced by pretreatment with the selective D-1 agonist SK&F 38393

When given alone, 2.5 mg/kg of the selective D-2 agonist RU 24213 was a threshold dose for the induction of weak stereotyped behaviour, while 15 mg/kg of the selective D-1 agonist SK&F 38393 failed to induce stereotypy. Responses to 2.5 mg/kg RU 24213 were dose-dependently potentiated by 3.0-15.0 mg/kg SK&F 38393, and compulsive stereotypy was only evident in animals receiving the combination treatment. Increasing D-1 dopaminergic activity appears to promote the expression of behaviours initiated through D-2 receptor stimulation.

Locomotor behaviors in response to new selective D-1 and D-2 dopamine receptor agonists, and the influence of selective antagonists

With the introduction of the selective D-1 dopamine receptor agonist and antagonist benzazepines, especially as enantiomeric pairs, there is now a range of D-1 compounds to complement the previously available selective D-2 agents. These have been used to investigate whether sub-types of dopamine receptors might be differentially involved in locomotor behavior. Stereotyped locomotion induced by the non-selective D-2 agonist apomorphine and by the selective D-2 agonist RU 24213 were blocked by the selective D-2 antagonists metoclopramide and Ro 22-2586 [-)-piquindone). Responses to either D-2 agonist were also blocked by the selective D-1 antagonists SCH 23390 and R-(but not S-) SK&F 83566. Non-stereotyped locomotion was induced by R- but not S-SK&F 38393, a stereoselective D-1 agonist, and was blocked by SCH 23390. Responses to the D-1 agonist were also antagonised by metoclopramide. Such results suggest concerted D-1:D-2 interplay in the regulation of at least some dopaminergic behaviors, such as locomotion.

A re-evaluation of changes in rat striatal D-2 dopamine receptors during development and aging

High affinity binding of 3H-spiperone to D-2 dopamine receptors was measured in membrane fractions prepared from striata of male Sprague-Dawley rats aged 0.75-25 months. 3H-Spiperone bound with approximately 0.11 nM affinity in all age groups studied. The maximum number of D-2 receptors initially increased with age, peak adult levels being reached by 4 months of age. Receptor density declined by 33% over the next 7 months and no further loss of receptors was apparent between 11 and 25 months of age. Such a time-course suggests a loss of rat D-2 receptors that occurs, at least in this strain, earlier than has previously been appreciated, and appears to be in agreement with preliminary positron emission tomographic studies in living man.

The enantiomers of SK&F 83566, a new selective D-1 dopamine antagonist, stereospecifically block stereotyped behaviour induced by apomorphine and by the selective D-2 agonist RU 24213

The non-selective dopamine receptor agonist apomorphine and the selective D-2 receptor agonist RU24213 each induced a typical syndrome of stereotyped behaviour characterised by sniffing and locomotion. The syndrome and its associated behaviours induced by each agonist were dose-dependently antagonised by pretreatment with the R- but not with the S-enantiomer of the benzazepine SK&F 83566. R- but not S-SK&F 83566 stereoselectively blocks D-1 receptors with high affinity, while the enantiomers have a very weak affinity for D-2 receptors which shows negligible stereoselectivity. Therefore, enantioselective blockade of brain D-1 receptors appears able to influence the expression of behaviours initiated by D-2 receptor stimulation.

Structural determinants of selective affinity for brain D-1 dopamine receptors within a series of 1-phenyl-1H-3-benzazepine analogues of SK&F 38393 and SCH 23390

A series of 1-phenyl-1H-3 benzazepine analogues of the D-1 agonist SK&F 38393 and of the D-1 antagonist SCH 23390 were compared for their relative abilities to displace the binding of [3H]piflutixol and [3H]spiperone to striatal D-1 and D-2 receptors respectively. The benzazepine analogues varied in substitutions at the 3- and 7-positions which distinguish SK & 38393 from SCH 23390. Substitutions at these positions critically influenced affinity for D-1 receptors over a 2000-fold range but influenced affinity for D-2 receptors over only a 30-fold range. 7-Substituents prominently increased affinity and selectivity for D-1 receptors with a rank order of Br = Cl much greater than CH3 greater than H greater than OH. 3-Methylation had a less marked and less selective action to increase affinity for D-1 receptors. Such structural relationships may aid the definition of the topography of brain D-1 receptors and the development of improved selective agents.

Association of intellectual impairment, negative symptoms, and aging with tardive dyskinesia: clinical and animal studies

It is not known why some schizophrenic patients receiving long-term neuroleptic treatment develop abnormal involuntary orofacial movements, while others do not. Schizophrenic patients with orofacial dyskinesia were found to be more intellectually impaired, more likely to show negative symptoms, and older than those without such movements. These features are characteristic of the "defect state," wherein structural brain changes may be demonstrable. Prolonged long-term neuroleptic treatment of young rats was associated with late-onset orofacial movements; however, such movements occurred spontaneously in untreated senescent rats. Structural brain changes consequent to aging and disease processes may be associated with the emergence of orofacial dyskinesia, even in the absence of exposure to neuroleptics. These movements do not appear to have their basis in striatal dopamine receptor supersensitivity.

Sniffing, rearing and locomotor responses to the D-1 dopamine agonist R-SK&F 38393 and to apomorphine: differential interactions with the selective D-1 and D-2 antagonists SCH 23390 and metoclopramide

The D-1 agonist R-SK&F 38393 induced non-stereotyped sniffing, rearing and locomotor responses that were blocked by the D-1 antagonist SCH 23390. The D-2 antagonist metoclopramide failed to block sniffing but blocked rearing and locomotion. Stereotyped sniffing and locomotion induced by apomorphine were each blocked by both antagonists. Either the criteria by which compounds are designated as D-1 or D-2 selective agents require revision, or else D-1 and D-2 mechanisms are able to reciprocally interact to influence the expression of behaviour initiated by stimulation of either receptor subtype.

Effects of the putative D-1 antagonist SCH 23390 on stereotyped behaviour induced by the D-2 agonist RU24213

The effects of the putative selective dopamine D-1 antagonist benzazepine SCH 23390 and of the selective dopamine D-2 antagonist Ro22-2586 on stereotypy induced by the selective D-2 agonist RU24213 were compared. RU24213 (0.5-15 mg/kg) dose-dependently induced stereo-typed behaviour characterised by continuous downward sniffing and locomotion. These responses were antagonised, as expected, by 40-200 micrograms/kg Ro22-2586, but surprisingly blocked by 40-200 micrograms/kg SCH 23390. The selectivities of these compounds for dopamine receptor subtypes were verified in terms of their relative abilities to displace the in vitro binding of 3H-piflutixol to striatal D-1 receptors and of 3H-spiperone to D-2 receptors. As SCH 23390 fails to influence D-2 mediated prolactin secretion or emesis in vivo, there appears to be no significant formation of an active metabolite of SCH 23390 with D-2 antagonist activity. Because SCH 23390 has some affinity for 5-hydroxytryptamine receptors, any effect on the serotonergic behavioural syndrome induced by 10 mg/kg 5-methoxy-N,N-dimethyltryptamine was also studied. The serotonergic responses of hind limb abduction, reciprocal forepaw treading and Straub tail were unaltered after 40-200 micrograms/kg SCH 23390, indicating no significant 5-HT blockade or non-specific depressant action at these doses which might influence the expression of stereotypy. Thus, these data are consistent with blockade of tonic D-1 dopaminergic activity that may influence the expression of behaviours initiated by D-2 dopaminergic stimulation.

Loss of rat striatal dopamine receptors with ageing is selective for D-2 but not D-1 sites: association with increased non-specific binding of the D-1 ligand [3H]piflutixol

The effects of age on the binding of dopaminergic ligands to rat striatal membranes were studied. When compared with four month old animals, at 22 months there was a significant decrease in the density of specific binding sites for the D-2 ligand [3H]spiperone while their affinity was unaltered. However, the specific binding of [3H]piflutixol to D-1 sites was unaltered between these age groups. The non-specific binding of [3H]piflutixol was significantly increased in aged preparations. Age-related loss of striatal D-2 dopamine receptors does not extend to the D-1 type. Alterations in non-specific [3H]piflutixol binding may reflect other pathophysiological changes associated with senescence.

Selective and stereospecific interactions of R-SK & F 38393 with [3H]piflutixol but not [3H]spiperone binding to striatal D1 and D2 dopamine receptors: comparisons with SCH 23390

Four benzazepine derivatives, racemic SK&F 38393, its resolved R- and S-enantiomers, and SCH 23390 have been investigated for their interactions with striatal D1 and D2 dopamine receptors, as indexed by the binding of [3H] piflutixol and [3H]spiperone respectively. For the agonist SK&F 38393, its R-enantiomer was active in displacing [3H] piflutixol while its S- antipode was 100 fold less potent. In contrast, both enantiomers showed similar and negligible activity to displace [3H]spiperone. SCH 23390, an antagonist analogue with an R-configuration, potently displaced [3H] piflutixol but not [3H]spiperone. R-SK&F 38393 and SCH 23390 may help clarify the structural requirements for, and functional consequences of, selective actions at the D1 dopamine receptor.

Dopaminergic behaviour stereospecific promoted by the D1 agonist R-SK & F 38393 and selectively blocked by the D1 antagonist SCH 23390

The selective D1 dopamine receptor agonist R-SK & F 38393 (20 mg/kg), but not its S- antipode , stereospecifically promoted episodes of prominent grooming behaviour. Typical stereotyped behaviour, such at that induced by apomorphine, was not seen. Grooming responses to 20 mg/kg R-SK & F 38393 were blocked by 0.1-0.5 mg/kg of the selective D1 antagonist SCH 23390 but not by 1.0-5.0 mg/kg of the selective D2 antagonist metoclopramide, while stereotyped behaviour induced by 0.5 mg/kg apomorphine was blocked by both antagonists. These results are consistent with certain individual dopaminergic behaviours such as grooming being mediated by D1 receptors. Other dopaminergic syndromes may involve complex functional interactions between D1 and D2 receptors.

[3H]R05-4864 and [3H]flunitrazepam binding in kainate-lesioned rat striatum and in temporal cortex of brains from patients with senile dementia of the Alzheimer type

In agreement with other workers we report increased [3H]R05-4864 binding in kainate-lesioned rat striatum. [3H]R05-4864 binding, a possible glial marker, was also increased in temporal cortex obtained post-mortem from patients with Alzheimer's disease. [3H]Flunitrazepam binding was decreased in these brain samples, possibly indicative of neuronal cell loss. It is suggested that the poor binding characteristics of [3H]R05-4864 in human brain samples may limit its usefulness in assessing gliosis.

Irreversible interaction of beta-haloalkylamine derivatives with dopamine D1 and D2 receptors

The interaction of beta-haloalkylamine derivatives of dopamine agonists and antagonists with 3H-spiperone binding (D2 sites) and 3H-flupenthixol binding (D1 sites) was studied. N-chloroethyl derivatives of phenothiazines and thioxanthenes were potent inhibitors of the binding of both ligands. The in vitro inhibition of binding produced by these compounds was irreversible. The drugs were however only weakly active in vivo. The results suggest that beta-haloalkylamine derivatives of neuroleptics may be useful compounds for studying dopamine receptors in vitro.