Oral dyskinesia in brain-damaged rats withdrawn from a neuroleptic: implication for models of tardive dyskinesia

Effects of cabergoline and rotigotine on tacrine-induced tremulous jaw movements in rats

OBJECTIVES

We examined the effects of two dopamine agonists, cabergoline and rotigotine, on tacrine-induced tremor and c-Fos expression in rats.

METHODS

Rats received intraperitoneal injection of cabergoline (0.5, 1.0, or 5.0mg/kg), rotigotine (1.0, 2.5, or 10.0mg/kg), or vehicle 30min before intraperitoneal injection of tacrine (5.0mg/kg). The number of tremulous jaw movements (TJMs) after tacrine administration was counted for 5min. Animals were sacrificed 2h later under deep anesthesia, and the brain sections were immunostained in order to evaluate the c-Fos expression.

RESULTS

Induction of TJMs by tacrine was dose-dependently reduced by pretreatment with cabergoline and rotigotine. The number of c-Fos-positive cells was significantly enhanced in the medial striatum, nucleus accumbens core, and nucleus accumbens shell after tacrine administration, and the enhanced expression of c-Fos in these three regions was significantly attenuated by cabergoline, while rotigotine suppressed c-Fos expression in two regions except the nucleus accumbens core.

CONCLUSIONS

These results suggest that tacrine-induced TJMs would be relieved by either cabergoline or rotigotine and that anticholinesterase-induced TJMs and the ameliorating effects of dopamine agonists would relate to neuronal activation in the striatum and nucleus accumbens.

Relevance of animal models to human tardive dyskinesia

Tardive dyskinesia remains an elusive and significant clinical entity that can possibly be understood via experimentation with animal models. We conducted a literature review on tardive dyskinesia modeling. Subchronic antipsychotic drug exposure is a standard approach to model tardive dyskinesia in rodents. Vacuous chewing movements constitute the most common pattern of expression of purposeless oral movements and represent an impermanent response, with individual and strain susceptibility differences. Transgenic mice are also used to address the contribution of adaptive and maladaptive signals induced during antipsychotic drug exposure. An emphasis on non-human primate modeling is proposed, and past experimental observations reviewed in various monkey species. Rodent and primate models are complementary, but the non-human primate model appears more convincingly similar to the human condition and better suited to address therapeutic issues against tardive dyskinesia.

Pharmacological and physiological characterization of the tremulous jaw movement model of parkinsonian tremor: potential insights into the pathophysiology of tremor

Tremor is a cardinal symptom of parkinsonism, occurring early on in the disease course and affecting more than 70% of patients. Parkinsonian resting tremor occurs in a frequency range of 3-7 Hz and can be resistant to available pharmacotherapy. Despite its prevalence, and the significant decrease in quality of life associated with it, the pathophysiology of parkinsonian tremor is poorly understood. The tremulous jaw movement (TJM) model is an extensively validated rodent model of tremor. TJMs are induced by conditions that also lead to parkinsonism in humans (i.e., striatal DA depletion, DA antagonism, and cholinomimetic activity) and reversed by several antiparkinsonian drugs (i.e., DA precursors, DA agonists, anticholinergics, and adenosine A(2A) antagonists). TJMs occur in the same 3-7 Hz frequency range seen in parkinsonian resting tremor, a range distinct from that of dyskinesia (1-2 Hz), and postural tremor (8-14 Hz). Overall, these drug-induced TJMs share many characteristics with human parkinsonian tremor, but do not closely resemble tardive dyskinesia. The current review discusses recent advances in the validation of the TJM model, and illustrates how this model is being used to develop novel therapeutic strategies, both surgical and pharmacological, for the treatment of parkinsonian resting tremor.

Validation of the tremulous jaw movement model for assessment of the motor effects of typical and atypical antipychotics: effects of pimozide (Orap) in rats

Drug-induced tremulous jaw movements (TJMs) in rats have been used as a model of parkinsonian tremor. Previous studies demonstrated that the typical antipsychotic haloperidol induced TJMs after acute or subchronic administration, while atypical antipsychotics did not. Moreover, it has been suggested that the relative potency for suppression of tacrine-induced TJMs relative to the suppression of lever pressing can be used to discriminate between typical and atypical antipsychotics. In order to validate this model with additional drugs, the present studies assessed the effects of the typical antipsychotic pimozide. In the first series of experiments, the effects of acute pimozide on tacrine-induced TJMs and lever pressing were examined. As with haloperidol, pimozide failed to suppress tacrine-induced TJMs, even at doses considerably higher than those that suppressed lever pressing. In the second group of experiments, rats were given single daily injections of pimozide (0.125-1.0 mg/kg) or tartaric acid vehicle for 13 days, and were observed for TJMs on days 1, 7, and 13. Pimozide induced TJMs in a dose-related manner on all days. The jaw movements occurred largely in the 3-7 Hz frequency range characteristic of parkinsonian tremor. These data support the hypothesis that typical antipsychotics can induce TJMs in rats, and demonstrate that chronic administration of typical antipsychotics is not necessary for induction of TJMs. TJMs induced by acute or subchronic pimozide may be related to early-onset motor syndromes such as drug-induced parkinsonism.

Relationship of orofacial movements to behavioural repertoire as assessed topographically over the course of 6-month haloperidol treatment followed by 4-month withdrawal

RATIONALE

Late-onset vacuous chewing movements (VCMs) arise in a significant proportion of rats treated chronically with conventional antipsychotic drugs. Given their common action to block dopamine D2-like receptors, VCMs may be related to changes in dopaminergic function; if so, other typical dopamine-mediated behaviours might be altered also.

OBJECTIVE

To examine this hypothesis, behavioural repertoire was studied topographically over the course of chronic treatment and withdrawal.

METHODS

Animals were injected with haloperidol decanoate 28 mg/kg IM, or vehicle, every 3 weeks for 27 weeks, and then maintained without treatment for a further 18 weeks. Immediately before each injection and during withdrawal, VCMs and other topographies of behaviour were assessed.

RESULTS

In both control and haloperidol-treated rats, exploratory behaviours declined over the study, indicating habituation effects. Conversely, VCMs emerged after 6 weeks of treatment with haloperidol and persisted after withdrawal; VCM and locomotion were not related, indicating that in treated rats, increased VCMs are not an artifact of reduced locomotion. Treated animals with VCMs evidenced increases in buccal tremor and grooming behaviour relative to those without VCMs, although no clear relationship to the emergence of VCMs was established; there were no material differences in any other topographies of behaviour.

CONCLUSION

The effect of long-term treatment with haloperidol to induce VCMs is not reflected in fundamental changes in dopamine-mediated behavioural topography but, rather, appears to affect neural mechanisms involved in orofacial movement preferentially.

The vacuous chewing movement (VCM) model of tardive dyskinesia revisited: is there a relationship to dopamine D(2) receptor occupancy?

Tardive dyskinesia (TD) is a late side effect of long-term antipsychotic use in humans, and the vacuous chewing movement (VCM) model has been used routinely to study this movement disorder in rats. Recent receptor occupancy studies in humans and rats have found that antipsychotics given in doses which lead to moderate levels of D(2) receptor blockade can achieve optimal clinical response while minimizing the emergence of acute motor side effects. This suggests that clinicians may have been using inappropriately high doses of antipsychotics. A review of the existing VCM literature indicates that most animal studies have similarly employed antipsychotic doses that are high, i.e. doses that lead to near complete D(2) receptor saturation. To verify whether the incidence or severity of VCMs would decrease with lower antipsychotic doses, we conducted initial experiments with different doses of haloperidol (HAL) given either as repeated daily injections or as depot injections over the course of several weeks. Our results demonstrate that (1) the incidence of VCMs is significantly related to HAL dose, and (2) significant levels of VCMs only emerge when haloperidol is continually present. These findings are consistent with the possibility that total D(2) occupancy, as well as 'transience' of receptor occupation, may be important in the development of late-onset antipsychotic-induced dyskinetic syndromes.

Tardive dyskinesia model in the common marmoset

Thirteen adult common marmosets (Callithrix jacchus) were given once-monthly injections of haloperidol decanoate (5-15 mg/kg i.m.) for one year. Thereafter, drug-free and treatment periods alternated at 3-month intervals. After 2.5 to 14 months, 12 monkeys showed symptoms of tardive dyskinesia (TD), such as periocular and perioral twitchings, tongue protrusions, masticatory movements, and choreic movements in arms and legs. When TD symptoms were evident, the periodic treatment was interrupted and symptoms persisted for at least 5 months after the last haloperidol dose, worsened by injection of the anticholinergic drug biperiden. An injection of nondepot haloperidol (0.12 or 0.25 mg/kg) produced a reduction of TD symptoms. At the end of the study, nondepot haloperidol was injected once a week at two doses (0.12 and 0.25 mg/kg i.m.). A syndrome of excitation with peculiar behavior, interpreted as acute dystonia, was precipitated in all animals. The animals showed sustained retrocollis, climbing upside down, biting the perch, repetitive turnings, and frequent backward movements. The dystonic movements lasted approximately 6 hours and were reduced but not completely extinguished by biperiden (0.1 mg/kg). The TD syndrome registered in marmosets may provide a useful model for screening new antipsychotics for their propensity to induce TD.

Tremulous jaw movements in rats: a model of parkinsonian tremor

Several pharmacological and neurochemical conditions in rats induce 'vacuous' or 'tremulous' jaw movements. Although the clinical significance of these movements has been a subject of some debate, considerable evidence indicates that the non-directed, chewing-like movements induced by cholinomimetics, dopamine antagonists and dopamine depletions have many of the characteristics of parkinsonian tremor. These movements occur within the 3-7 Hz peak frequency range that is characteristic of parkinsonian tremor. Tremulous jaw movements are induced by many of the conditions that are associated with parkinsonism, and suppressed by several different antiparkinsonian drugs, including scopolamine, benztropine, L-DOPA, apomorphine, bromocriptine, amantadine and clozapine. Striatal cholinergic and dopaminergic mechanisms are involved in the generation of tremulous jaw movements, and substantia nigra pars reticulata appears to be a major basal ganglia output region through which the jaw movements are regulated. Future research on the neurochemical and anatomical characteristics of tremulous jaw movements could yield important insights into the brain mechanisms that generate tremulous movements.

Effects of dopaminergic drugs, occlusal disharmonies, and chronic stress on non-functional masticatory activity in the rat, assessed by incisal attrition

Observational methods and the recording of nonspecific jaw movements or masticatory muscle activity have been used to evaluate oral parafunctional movements in animal models of bruxism. In this study, we have used a new approach in which the non-functional masticatory activity in the rat was assessed by the measurement of incisal attrition, with the aim of investigating the role of diverse factors involved in the etiology of bruxism. We quantified the attrition rate weekly by making superficial notches in the lower incisors and measuring the distances to the incisor edges. Repeated stimulation of the dopaminergic system with apomorphine led to an enhancement of the non-functional masticatory activity (p < 0.0001). The severity of the apomorphine-induced oral behavior was positively correlated (r(s) = 0.69, p < 0.01) with an increase in the incisal attrition rate (20.9%, p < 0.0001). Apomorphine-induced non-functional masticatory activity was strongly enhanced by the placement of an acrylic cap on both lower incisors (306%, p < 0.0001), but not by the cutting of a lower incisor. Repeated cocaine administration also increased the attrition rate (22.5%, p < 0.0001). However, neither chronic blockade of dopaminergic receptors with haloperidol, nor its withdrawal, modified attrition. In addition, since emotional disturbances are considered to be causal factors of bruxism, we tested whether experimental stress might accelerate tooth wear. Exposure to two different chronic stress regimes did not induce significant changes in incisal attrition. Moreover, exposure to chronic stress after the withdrawal of chronic haloperidol treatment did not alter attrition either. These results partially support the role of the central dopaminergic system in bruxism and suggest that stress, in general, may not be a relevant factor in tooth wear.

Emergence of oral and locomotor activity in chronic haloperidol-treated rats following cortical N-methyl-D-aspartate stimulation

Neuroleptic-induced orofacial movements in rats have been widely utilized as an animal model of tardive dyskinesia (TD). The present study investigated the role of the oral motor cortex in these movements by applying direct cortical stimulation in rats exposed to chronic haloperidol. Rats received depot i.m. injections of haloperidol decanoate or sesame oil vehicle every 3 weeks (10 rats per group). After 24 weeks of injections and a 3-week withdrawal period, bilateral guide cannulae were implanted into the primary oral motor cortex. After a 1-week recovery, bilateral microinfusions of saline vehicle followed by 1, 3, and 10 mM N-methyl-D-aspartate (NMDA) were given and observations of oral activity, locomotion, rearing, and grooming were recorded. Haloperidol-treated rats displayed a significant emergence of NMDA stimulated oral activity (nondirected oral movements, oral tremor, audible teeth grinding, and directed oral movements). In addition, rearing and locomotion were significantly elevated in these animals. In contrast to haloperidol-treated rats, sesame oil-treated rats showed no significant emergence of any motor activity. These results suggest that chronic haloperidol administration alters primary motor cortex efferents, and that this effect may be a factor in the manifestation of chronic neuroleptic induced motor side effects, such as TD.

Effects of clozapine and haloperidol on baseline levels of vacuous jaw movements in aged rats

Some studies have indicated that aged rats have elevated basal levels of vacuous jaw movements and these vacuous jaw movements are exacerbated by classic neuroleptic drugs like haloperidol, but the effects of the atypical antipsychotic clozapine on vacuous jaw movements in aged rats has not previously been studied. Aged rats were administered daily intraperitoneal injections of either haloperidol (0.04, 0.1 or 0.4 mg/kg), clozapine (0.4, 1.0, 4.0 mg/kg) or 0.3% tartaric acid vehicle for 22 days. On days 1, 8, 15 and 22 these rats were placed in an observation tube and vacuous jaw movements were recorded by two trained observers. Vacuous jaw movements were present in the aged rats receiving vehicle. Haloperidol produced a dose-dependent increase in vacuous jaw movements while clozapine produced a dose-dependent attenuation of vacuous jaw movements, relative to the vehicle-treated rats. These results indicate that screening for vacuous jaw movements may provide a useful behavioral assay for atypical antipsychotic drugs which do not produce extrapyramidal side effects and that clozapine's resistance to these side effects may extend to populations of elderly human patients.

Single restraint stress sensitizes acute chewing movements induced by haloperidol, but not if the 5-HT1A agonist 8-OH-DPAT is given prior to stress

The objective of this study was two-fold: (i) to analyze behavioral sensitization to haloperidol 2 weeks after single restraint stress, and (ii) to establish the effects of 8-OH-DPAT treatment prior to stress on sensitized behavioral responses. Overall behavior was analyzed and not only catalepsy, but also sedation (immobility), grooming, exploration and vacuous chewing movements were evaluated. Results indicated that single restraint stress induced a long-lasting sensitization of acute vacuous chewing movements induced by haloperidol (0.25, 0.5 mg/kg i.p.). Interestingly, this behavioral sensitization was prevented by 8-OH-DPAT (0.35 mg/kg s.c.) prior to stress. Finally, haloperidol-induced sedation was not disrupted by either restraint stress or 8-OH-DPAT treatment.

Tremulous characteristics of the vacuous jaw movements induced by pilocarpine and ventrolateral striatal dopamine depletions

Vacuous jaw movements induced by the muscarinic agonist pilocarpine and striatal dopamine depletions were examined using a slow motion videotape system. With this procedure, rats were videotaped in a Plexiglas tube so that the profile of the head region could be seen. Vacuous jaw movements were analyzed by examining the tape at 1/6 normal speed. An observer recorded each jaw movement using a computer, and the computer program re-calculated the temporal characteristics of jaw movement responses back to normal speed. The interresponse time was recorded for each jaw movement, and each jaw movement interresponse time was assigned to a 50 ms wide time bin. Thus, the distribution of interresponse times could be used to analyze the temporal characteristics of jaw movement responses. In the first experiment, rats were administered saline vehicle, 1.0 mg/kg and 2.0 mg/kg pilocarpine. The rats were videotaped 10-15 min after injection, and the data were analyzed as described above. Pilocarpine induced very high levels of vacuous jaw movements, and the vast majority of all movements occurred in "bursts" with interresponse times of 1.0 s or less. Analysis of the interresponse time distributions showed that most of the jaw movements were within the 150-350 ms range. The modal jaw movement interresponse time was in the 150-200 ms range, which corresponds to a local frequency of 5-6.66 Hz. In the second experiment, the neurotoxic agent 6-hydroxydopamine was injected directly into the ventrolateral striatum in order to produce a local dopamine depletion. The dopamine-depleted rats were observed for jaw movements 7 days after surgery. The overall level of jaw movement activity resulting from dopamine-depletion was much lower than that produced by pilocarpine. There was a significant inverse correlation between ventrolateral striatal dopamine levels and total number of vacuous jaw movements. Videotape analysis indicated that the temporal characteristics of jaw movements induced by dopamine depletions were similar to those shown with pilocarpine. These experiments indicate that vacuous jaw movements induced by pilocarpine and striatal dopamine depletion occur in a frequency range similar to that shown in parkinsonian tremor.

Effects of rating parameters on assessment of neuroleptic-induced vacuous chewing movements

Long-term administration of neuroleptics to rats produces a syndrome of vacuous chewing movements (VCMs). The validity of the VCM syndrome as a model for tardive dyskinesia (TD) in humans is unclear. This is due, in part, to inconsistencies between studies. Methods for rating VCMs have varied markedly and could account for the inconsistencies. The purpose of this study was to evaluate the importance of the different methods on VCM scores. The effects of habituation and length of rating sessions were examined in rats habituated for 2 min, 1 h, or several hours over 4 days, compared to unhabituated rats. Ratings with and without habituation were highly correlated, as were ratings from 2- and 5-min observation periods. Ratings from neuroleptic-treated rats in restraining tubes, however, were significantly correlated with unrestrained ratings only following several hours of habituation. Locomotor activity was not correlated with VCM scores. These results suggest that habituation to open cages is not an important factor in assessing VCMs. Use of restraining tubes, however, may alter scores. The lack of an habituation effect or of a relationship between activity and VCMs suggests that locomotor and oral behaviors are not necessarily in competition. Restraining rats to rate VCMs does not appear to be necessary and could alter the neurobiology of VCMs.

Suppression of oro-facial movements by rolipram, a cAMP phosphodiesterase inhibitor, in rats chronically treated with haloperidol

We investigated the effects of rolipram, a selective cyclic adenosine 3',5'-monophosphate phosphodiesterase type IV inhibitor, and isobutylmethylxanthine, a nonselective phosphodiesterase inhibitor, on purposeless spontaneous chewing movements and tongue protrusions produced by 24 weeks treatment with haloperidol decanoate (25 mg/kg every 4 weeks i.m.) in rats, to examine our hypothesis that restoration of striatal cyclic adenosine 3',5'-monophosphate levels previously reduced due to dopamine D2 receptor supersensitivity, may suppress these movements. Tests were performed 8 weeks after the final injection. Haloperidol treatment significantly increased dyskinetic movements and striatal dopamine D2 receptor density compared with controls. Rolipram (0.1-1.0 mg/kg i.p.) suppressed these movements in a dose-dependent manner, whereas isobutylmethylxanthine (2 mg/kg i.p.) only slightly suppressed the syndrome and doses higher than 5 mg/kg i.p. produced other intensive movements. These results support our hypothesis and suggest that rolipram may have a therapeutic effect on tardive dyskinesia.

Persistent oral dyskinesias in haloperidol-withdrawn neonatal 6-hydroxydopamine-lesioned rats

Because chronic haloperidol-treated rats demonstrate an increased incidence of spontaneous oral activity, while neonatal 6-hydroxydopamine-lesioned rats demonstrate an increased incidence of dopamine agonist-induced oral activity, we studied the influence of haloperidol in 6-hydroxydopamine-lesioned rats. At 3 days after birth rats received 6-hydroxydopamine hydrobromide (200 micrograms intracerebroventricularly; desipramine pretreatment, 20 mg/kg i.p., 1 h) or vehicle. Two months later haloperidol (1.5 mg/kg per day x 2 days per week, for 4 weeks; then 1.5 mg/kg per day, every day for 10 months) was added to the drinking water. After 15 weeks the level of spontaneous oral activity was stable. At 11 months there were 35.8 +/- 4.9 vs. 18.4 +/- 2.1 oral movements in 6-hydroxydopamine-lesioned vs. intact rats receiving haloperidol. This effect persisted unabated in lesioned rats for 4 months after haloperidol withdrawal. This stable high frequency of oral dyskinesias is an advantage for studying putative therapeutic drugs for tardive dyskinesia.

Possible genetic factors underlying the pathophysiology of tardive dyskinesia

Rates of spontaneous and drug-induced repetitive jaw movements (RJM) in rats vary widely. Low and high RJM responders were isolated and genetically selected. At each generation mean RJM responses (spontaneous or SKF 38393-induced) of the two types of rats were found to differ significantly, whereas neither apomorphine-induced stereotypic responses nor D1 and D2 receptor numbers and affinities differed. A significant increase in cAMP production was evident in SKF 38393-stimulated striatal homogenates of high RJM responders as compared with low responders. Animals subjected to 8-months exposure to fluphenazine exhibited RJM that were about twice as great as that of controls, 2 months after the last treatment, with a prevalence of about 75%. Similarities between RJM observed in rats and neuroleptic-induced tardive dyskinesia suggest that the two are strongly related.

Repeated scopolamine injections sensitize rats to pilocarpine-induced vacuous jaw movements and enhance striatal muscarinic receptor binding

This experiment was conducted to determine if repeated administration of the muscarinic antagonist scopolamine could increase pilocarpine-induced vacuous jaw movements and also enhance muscarinic receptor binding. Rats received daily injections of either scopolamine (0.5 mg/kg IP) or saline for 14 days. On day 15 rats received no injections of scopolamine, but did receive injections of pilocarpine (1.0, 2.0 or 4.0 mg/kg IP) or saline. After administration of pilocarpine or saline, all rats were observed for vacuous jaw movements and rearing behavior. The day after pilocarpine injections, rats were sacrificed and samples of tissue from the lateral neostriatum were removed to assess muscarinic receptor binding using 3H-QNB as the ligand. Analyses of the vacuous jaw movement data indicated that there was a significant dose-related increase in vacuous jaw movements induced by pilocarpine, and also that there was a significant enhancement of pilocarpine-induced vacuous jaw movements in rats pretreated with repeated scopolamine injections. There was not a significant scopolamine x pilocarpine interaction, suggesting that pretreatment with scopolamine produced an apparent parallel shift in the pilocarpine dose-response curve. Pilocarpine significantly suppressed rearing behavior, and scopolamine pretreatment significantly enhanced the suppression of rearing produced by pilocarpine. Analysis of the receptor binding data indicated that there was a significant increase in the number of muscarinic receptor sites (Bmax) in rats that received repeated scopolamine injections as compared to saline-treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Vacuous jaw movements in rats induced by acute reserpine administration: interactions with different doses of apomorphine

Two experiments were conducted to study the vacuous jaw movements induced in rats by acute administration of the monoamine-depleting agent reserpine. In the first experiment, different doses of reserpine (1.25, 2.5, and 5.0 mg/kg) were assessed for their ability to induce vacuous jaw movements. Acute administration of reserpine induced a dose-related increase in vacuous jaw movements, with the two highest doses being significantly different from the vehicle control. In the second experiment, interactions between 5.0 mg/kg reserpine and the dopamine agonist apomorphine were investigated. Coadministration of reserpine with the lowest dose of apomorphine (0.1 mg/kg) significantly increased vacuous jaw movements relative to reserpine alone. The two higher doses of apomorphine (0.5 and 1.0 mg/kg) significantly decreased vacuous jaw movements in reserpine-treated rats. These results demonstrate that vacuous jaw movements are induced by acute reserpine treatment in a dose-related manner. In addition, the interactions with apomorphine suggest that vacuous jaw movements are stimulated by decreases in dopamine release produced by low doses of apomorphine that are thought to have mainly presynaptic actions, but that these movements are decreased by higher doses of apomorphine that are known to act postsynaptically.

Effects of acute haloperidol and reserpine administration on vacuous jaw movements in three different age groups of rats

In these experiments three different age groups of rats were tested for vacuous jaw movements. The age groups included rats aged 3 months, rats aged 6-9 months, and rats aged 12-15 months. In the first experiment, rats were given a single IP injection of either 0.3% tartaric acid vehicle or 0.4 mg/kg haloperidol. In the second experiment, rats were given injections of vehicle or 5.0 mg/kg reserpine. Haloperidol and reserpine significantly increased vacuous jaw movements. There were significant effects of age on vacuous jaw movements, with rats aged 6-9 months and rats aged 12-15 months showing more jaw movements than 3-month-old rats. In both experiments, the drug x age interaction was not significant, indicating that the combined effects of age and neuroleptic treatment were additive and not synergistic. Haloperidol and reserpine also reduced rearing behavior in all age groups. It is concluded that age is an important variable in studies of vacuous jaw movements.

Treatment of schizophrenia: a clinical and preclinical evaluation of neuroleptic drugs

Forty years after the first clinical report on the effectiveness of chlorpromazine in psychiatric patients, neuroleptic drugs are still the most widely used drugs in the treatment of schizophrenia. Indeed, there are no other drugs which have proven to be as effective in the treatment of this severe psychiatric disorder. Yet, there are still many unresolved problems relating to neuroleptic drugs. The present review gives a comprehensive overview of our knowledge (and our lack of knowledge) with respect to the clinical and preclinical effects of neuroleptic drugs and tries to integrate this knowledge in order to identify the neuronal mechanisms underlying the therapeutic and side effects of neuroleptic drugs.

Vacuous jaw movements induced by sub-chronic administration of haloperidol: interactions with scopolamine

The present series of experiments was conducted to investigate the vacuous jaw movements induced by sub-chronic administration of haloperidol (HP). In the first experiment, daily injection of 0.4 mg/kg HP for 10 days increased vacuous jaw movements and decreased rearing behavior. The second and third experiments investigated the interaction between the effects of HP and the anticholinergic drug scopolamine. Co-administration of 0.5 mg/kg scopolamine with 0.4 mg/kg HP for 9 days reduced vacuous jaw movements and increased rearing responses relative to rats that received HP alone. Co-administration of HP with 0.25 mg/kg scopolamine for 9 days increased rearing relative to rats that received HP alone, but there was no effect of the lower dose of scopolamine on vacuous jaw movements. Administration of 0.5 mg/kg scopolamine plus 0.4 mg/kg HP on days 11-14 to rats that had received HP alone for 10 days reversed the effect of HP on rearing, but not on vacuous jaw movements. Rats that had received HP plus scopolamine for 10 days showed dramatic increases in vacuous jaw movements when scopolamine was withdrawn. Because vacuous jaw movements are produced within the first few days of administration, reduced by administration of scopolamine, and exacerbated by withdrawal of scopolamine, the pharmacological characteristics of these movements do not appear to bear a close relation to those of tardive dyskinesia in humans. The present results are consistent with the hypothesis that vacuous jaw movements in rats share some characteristics with Parkinsonian symptoms.

Effect of chronic trifluoperazine administration and subsequent withdrawal on the production and persistence of perioral behaviours in two rat strains

The effect of chronic administration of trifluoperazine on the perioral movement profile of Wistar and Sprague-Dawley rats was examined. Perioral movements were characterised by visual observations, coupled with electromyographic recording from the masseter muscle. In drug-naive animals from both strains the spectrum of perioral behaviours was essentially identical, primarily consisting of purposeless chewing, accompanied by occasional bursts of facial tremor and teeth chattering, with occasional yawning. Each burst of facial tremor was accompanied by a transient increase in the rate of purposeless chewing. Wistar rats exhibited a higher level of spontaneous purposeless chewing compared to Sprague-Dawley rats. In both strains, chronic administration of trifluoperazine (5 mg/kg per day, PO) for 5 months induced an increase in perioral behaviour, which primarily consisted of enhanced purposeless chewing. In Wistar rats the drug-induced increase in purposeless chewing was accompanied by an increase in the incidence of yawning, with no change in the incidence of either facial tremor or teeth chattering. In contrast, Sprague-Dawley rats displayed a drug-induced increase in purposeless chewing, accompanied by an increase in the incidence of facial tremor and teeth chattering, but not yawning. In Wistar rats withdrawal of trifluoperazine diminished but did not reverse the drug-induced increase in purposeless chewing. Drug withdrawal also precipitated a transient increase in the incidence of facial tremor and teeth chattering, but had no effect on yawning. In Wistar rats, the level of purposeless chewing and the incidence of yawning remained elevated above control levels for at least 13 weeks after drug withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroradiological covariates of drug-induced parkinsonism and tardive dyskinesia in schizophrenia

Computed tomographic (CT) studies have demonstrated structural brain abnormalities including cortical atrophy and enlarged lateral ventricles in a subset of schizophrenic patients including those with abnormal involuntary movements. In the following series of studies, we present our findings pertaining to neuroradiological covariates of drug-induced Parkinsonism and Tardive dyskinesia in schizophrenic patients. In these studies we have explored the relationship of Parkinsonism and Tardive dyskinesia to pineal and choroid plexus calcification. In addition, we also investigated the relationship of pineal calcification to schizophrenia, and specifically to the paranoid and nonparanoid subgroups. In a further series of studies, we investigated the neuroradiological covariates of disorders of gait and posture as well as tremor in schizophrenic patients with drug-induced Parkinsonism. In addition, we explored the relationship of Tardive dyskinesia and its subsyndromes to CT scan measurements of cortical and subcortical atrophy in schizophrenia. Our findings highlight the significance of the pineal gland in the pathophysiology of schizophrenia and drug-induced movement disorders. Furthermore, these studies underscore the heterogeneity of Parkinsonism and Tardive dyskinesia.

Drug-induced purposeless chewing: animal model of dyskinesia or nausea?

Drug-induced purposeless chewing movements in rodents are often considered to represent movement disorders or dyskinesias. We have compared the ability of drugs to induce chewing and retching or emesis in squirrel monkeys; such studies are not possible in rodents, which do not vomit. Acute administration of oxotremorine (3.3-33 micrograms/kg IM), SKF38393 (1-30 mg/kg SC) or ipecacuanha (0.5-0.75 mg/kg PO) caused dose-related increases in purposeless chewing which was frequently associated with retching and emesis. Treatment with haloperidol (0.015-0.06 mg/kg IM) did not induce chewing. Rather, haloperidol decreased spontaneous chewing at doses of 0.03 and 0.06 mg/kg. Our findings indicate that at least some drug-induced oral behaviours in rodents may reflect nausea rather than dyskinesia.

Lateral striatal cholinergic mechanisms involved in oral motor activities in the rat

These experiments were undertaken to determine if local injection of pilocarpine in the neostriatum of the rat produces oral motor activities that are similar to those produced by systemic administration. In the first experiment, IP administration of 2.0-8.0 mg/kg pilocarpine increased chewing movements and tongue protrusions. In the second experiment, chronic guide cannulae were implanted bilaterally in ventromedial or ventrolateral striatum, and rats were injected with saline, 30, and 60 micrograms pilocarpine (per side). A dose-related increase in vacuous chewing was induced by injections of pilocarpine in the ventrolateral but not the ventromedial striatum. Tongue protrusions were induced by injections of pilocarpine into the ventromedial and the ventrolateral striatum. A third experiment demonstrated that this response was blocked completely by 10 micrograms scopolamine co-administered via the same cannulae, but the response was not reduced significantly by 10 micrograms haloperidol. These results indicate that ventrolateral striatal cholinergic mechanisms are involved in oral motor activities in the rat. This syndrome may provide a model for human clinical phenomena such as parkinsonian tremor.

Methylazoxymethanol (MAM)-induced brain lesion and oral dyskinesia in rats

The effects of methylazoxymethanol (MAM)-induced brain lesions on vacuous chewing movements (VCM) were examined in rats given chronic haloperidol treatment (0.1 or 1 mg/kg/day) for 18 months. At the end of the experiment striatal, pallidal, and nigral activities of glutamate decarboxylase (GAD) were measured. MAM-lesioned rats had an elevated rate of VCMs compared to unlesioned controls. This effect was stable during the whole 18-month experiment. In unlesioned control rats chronic haloperidol produced a gradual increase in VCM rates, but this effect was not further exacerbated in MAM-lesioned animals. After chronic haloperidol treatment with the higher dose (1 mg/kg/day) GAD activity was reduced in substantia nigra (-20%), globus pallidus (-35%), and striatum (-26%) of unlesioned rats. MAM caused a reduction of GAD activity in substantia nigra (-29%) and globus pallidus (-29%). Chronic haloperidol did not influence these effects of MAM-induced lesion. The present results show that a MAM-induced brain lesion, in contrast to cortical ablations, cannot be used to amplify the haloperidol-induced VCM increase or influence the nigral GAD activity in a rat model for tardive dyskinesia.

Spontaneous orofacial movements induced in rodents by very long-term neuroleptic drug administration: phenomenology, pathophysiology and putative relationship to tardive dyskinesia

While understanding of the major clinical and ethical issue of tardive dyskinesia would be greatly facilitated by the development of an isomorphic or homologous animal model, particularly in rodents, this has proved to be a highly contentious issue. The literature on orofacial function in rats administered neuroleptic drugs for substantial proportions of their adult lifespan is reviewed. It reveals the emergence of late-onset orofacial movements in a number of studies, but very early-onset movements or no effect in others. Potential explanations for these discrepancies are considered, and ways of resolving such inconsistencies are suggested. The relationship of these various orofacial phenomena to dopaminergic and non-dopaminergic function, and to clinical syndromes, is critically evaluated.

Delayed appearance of facial tics following chronic fluphenazine administration to guinea pigs

Guinea pigs were administered chronic fluphenazine decanoate for 11 months and oral movements (OMs) were periodically observed using several different paradigms. Shortly after the initiation of neuroleptic treatment, increased OMs were seen in the drugged animals, but these did not persist and may have reflected a decreased fear (freezing) reaction in the tranquilized animals, being correlated with increased locomotion in open field. After 7 months of neuroleptics, twitch-like movements of the orofacial region were observed in the drugged animals; these dyskinetic movements were enhanced by administration of d-amphetamine. These twitch-like movements appear to be a better model of tardive dyskinesia in the guinea pig than the initially observed and normal-appearing OMs.

Chronic neuroleptic effects on spatial reversal learning in monkeys

Cebus apella monkeys were chronically administered the antipsychotic drug fluphenazine decanoate for periods ranging from 3.5 to 5.5 years. In the present study, four of these monkeys and two controls were tested for cognitive abilities on a spatial learning task, which consisted of an original discrimination and four reversals of that discrimination. No effect of fluphenazine administration was seen in the rate of learning the original discrimination, but the carryover of learning across discrimination reversals was significantly reduced by fluphenazine. After overtraining on the original discrimination, the controls showed the normal difficulty in learning the first reversal. The fluphenazine-treated monkeys showed no such disruption. On subsequent reversals, the controls showed continually improving performance, so that on the third and fourth reversals they had near-perfect scores. On the other hand, the fluphenazine-treated monkeys showed no change over the four reversals. Unlike normal monkeys, their learning did not improve with practice. Although simple forms of learning seem to be relatively unaffected by chronic fluphenazine administration, more complex learning is disrupted.

Neuroleptic side effects: acute extrapyramidal syndromes and tardive dyskinesia

The neuroleptic-induced motor system side effects of acute extrapyramidal syndromes (EPS) and tardive dyskinesia (TD) are the major limitations of these drugs. Effective strategies for managing these problems are based on the clinical presentations, pathophysiological processes, and a complex interaction of patient and treatment variables. New concepts about the causes and long-term outcome of acute EPS and TD are emerging to challenge some of the commonly held views about these syndromes. The primary method of preventing undue side effects is to use the lowest effective dose of both neuroleptic and anti-EPS drugs. The pressing need is for novel compounds which treat schizophrenia and are free of the undesirable motor system effects (a nonneuroleptic neuroleptic).

Neuroleptic-induced oral dyskinesias: effects of progabide and lack of correlation with regional changes in glutamic acid decarboxylase and choline acetyltransferase activities

The development of vacuous chewing movements (VCMs), and changes in glutamic acid decarboxylase (GAD) and choline acetyltransferase (ChAT) activities in extrapyramidal nuclei were examined in rats treated chronically with neuroleptics. Animals were injected with flupenthixol (FLU) or haloperidol (HAL) decanoate for 16, 40 or 48 weeks and were then sacrificed. Another group of rats was treated with FLU or HAL for 48 weeks, and then withdrawn from the neuroleptics for 16 weeks before sacrifice. VCMs were assessed weekly, and the effects of the GABA agonist progabide on VCMs and locomotor activity were examined. GAD and ChAT activities were determined at death. The concentrations of Calbindin D28K (CaBP) and parvalbumin (PV) were determined in rats receiving 48 weeks of neuroleptic treatment. VCMs first appeared after 8-10 weeks of neuroleptic administration, reached asymptotic rates after 18-20 weeks, and then remained stable for the remainder of the chronic drug administration period. During withdrawal, there was a steady decline in the VCM rate. The GABA receptor agonist progabide reduced VCMs and locomotor activity. Significant decreases in nigral GAD activity were observed after 40, but not after either 16 or 48 weeks of neuroleptic administration. CaBP and PV were unchanged after 48 weeks of neuroleptic treatment. In addition, ChAT activities in 16, 40 or 48 week treated animals did not show consistent changes after either neuroleptic. Chronic neuroleptic administration followed by 16 weeks of withdrawal also did not have any significant effects on GAD or ChAT activity in any of the brain areas examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Noradrenergic and neuroradiological abnormalities in tardive dyskinesia

Previous studies suggest that catecholaminergic overactivity and structural brain damage may contribute to the pathogenesis of tardive dyskinesia (TD). Although dopaminergic (DA) mechanisms, specifically postsynaptic receptor supersensitivity, have been extensively studied, equally plausible noradrenergic (NE) changes have been all but ignored. Likewise, the interaction of neurochemical and neuroradiological abnormalities has received little attention. Over the past 6 years, 111 inpatients were studied with a battery of neurological, behavioral, biochemical, and neuroradiological measures. Forty-one patients met specific diagnostic criteria for TD, based in part on global ratings on the Abnormal Involuntary Movement Scale. Subgroups of patients were also evaluated with the Brief Psychiatric Rating Scale and were assayed for plasma dopamine-beta-hydroxylase (DBH) activity, platelet 3H-dihydroergocryptine (3H-DHE)-alpha 2 adrenergic receptor binding, lumbar cerebrospinal fluid (CSF) monoamines and metabolites [NE, 3-methoxy-4-hydroxyphenylglycol (MHPG), DA-sulfate, homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC)], and CT scan indices of brain atrophy, including ventricle/brain ratio (VBR), bifrontal/bicaudate ratio, and cortical atrophy. All patients were studied in the steady state, primarily when free of neuroleptics. Patients with TD had significantly greater DBH activity than those without TD. In addition, 3H-DHE binding and CSF NE were significantly correlated with the severity of TD when present. Finally, TD patients with low DBH activities (below the mean) had significantly larger ventricles than non-TD patients with low DBH activities. Other data suggested that subcortical, rather than cortical, atrophy was more likely to be responsible for the larger VBR in the low DBH TD group. These results suggest an association of NE overactivity and TD in a portion of patients. Moreover, the presence of neuroradiological abnormalities in TD patients with low DBH activity underscores the contribution of heterogeneous factors to the pathogenesis of this disorder and may provide one possible explanation for the discrepant biochemical findings in TD reported by earlier investigators.

Chronic treatment with clozapine, unlike haloperidol, does not induce changes in striatal D-2 receptor function in the rat

Comparison has been made of the effects on brain dopamine function of chronic administration of haloperidol or clozapine to rats for up to 12 months. In rats treated for 1-12 months with haloperidol (1.4-1.6 mg/kg/day), purposeless chewing jaw movements emerged. These movements were only observed after 12 months' treatment with clozapine (24-27 mg/kg/day). Apomorphine-induced (0.125-0.25 mg/kg) stereotyped behaviour was inhibited during 12 months treatment with haloperidol. Clozapine treatment was without effect. After 12 months, stereotypy induced by higher doses of apomorphine (0.5-1.0 mg/kg) was enhanced in haloperidol, but not clozapine, treated rats. Bmax for striatal 3H-spiperone binding was elevated throughout 12 months of haloperidol administration, but was not altered by clozapine treatment. Bmax for striatal 3H-NPA binding was only elevated after 12 months of haloperidol treatment; clozapine treatment was without effect. Bmax for 3H-piflutixol binding was not altered by haloperidol treatment, but was increased after 9 and 12 months of clozapine treatment. Dopamine (50 microM)-stimulated adenylate cyclase activity was inhibited after 1 month's haloperidol treatment but normal thereafter. Adenylate cyclase activity was not altered by chronic clozapine treatment. Striatal acetylcholine content was increased after 3 and 12 months of haloperidol or clozapine intake. These findings indicate that the chronic administration of the atypical neuroleptic clozapine does not produce changes in brain dopamine function which mirror those of the typical neuroleptic haloperidol. In particular, chronic administration of clozapine, unlike haloperidol, does not appear to induce striatal D-2 receptor supersensitivity. Unexpectedly, clozapine treatment, unlike haloperidol, altered D-1 receptor function.

Cognitive performance of medicated schizophrenics with tardive dyskinesia

Twenty schizophrenic patients with tardive dyskinesia and an equal number of matched controls were tested on a novel cognitive task. The task had two components: cued response and spatial memory. Relative to controls, the dyskinetic subjects showed a superior cued response performance but an equal spatial memory ability. We speculate that this selective facilitation may reflect dopaminergic hyperactivity in the dyskinetic group.

Pharmacological characterisation of spontaneous or drug-associated purposeless chewing movements in rats

Continuous administration of haloperidol, sulpiride, or cis-flupenthixol, but not of domperidone or apomorphine, to Wistar rats for up to 3 weeks caused an increase in spontaneous purposeless chewing movements. Treatment with physostigmine and pilocarpine, but not neostigmine, for up to 3 weeks increased chewing, whilst scopolamine decreased chewing. Metergoline and cyproheptadine, but not quipazine, increased chewing after only 1 and 7 days but not thereafter. Chewing was not altered following treatment with compounds acting on GABA or noradrenaline systems or by a range of non-neuroleptic agents inducing dystonia in man. The enhancement of chewing induced by neuroleptic and cholinomimetic drugs was reduced by acute treatment with scopolamine, and reverted to control levels following drug withdrawal. Neuroleptic-induced purposeless chewing in Wistar rats appears to be primarily influenced by cerebral dopamine and acetylcholine function and may resemble acute dystonia, rather than tardive dyskinesia.

Induction of oral dyskinesias in naive rats by D1 stimulation

Repetitious opening and closing of the mouth and high frequency clonic jaw movements were observed in rats challenged with dopamine agonists after acute treatment with sulpiride or a low dose of spiroperidol. SKF 38393, a specific D1 receptor agonist, alone, also induced these behaviors and cis-flupenthixol blocked them, evidence suggesting D1 dopamine receptor mediation.

Reduction of nigral glutamic acid decarboxylase in rats with neuroleptic-induced oral dyskinesia

Following eight monthly haloperidol decanoate injections rats showed an increased rate of vacuous chewing movements (VCM's), which gradually disappeared within 4 drug-free months. Another single dose of non-decanoate haloperidol reinstated a second increase in VCM rate which was still significant after 2 months. The glutamic acid decarboxylase (GAD) activity in the substantia nigra of these chronically haloperidol-treated rats was lower than untreated controls. Furthermore, there was a significant negative correlation between individual VCM rates and nigral GAD activity. No corresponding changes occurred in other brain regions. The depression of nigral GAD may reflect a reduced tissue density of GABA-ergic axon terminals within the descending striato-nigral pathway.

Failure to find electrophysiological correlates of chronic neuroleptic-induced oral dyskinesias in cats: somatosensory and substantia nigra evoked potentials, electroencephalogram, and caudate spindles

Each of nine cats was prepared with 30 chronically implanted stainless steel gross electrodes in cortex, basal ganglia and other brain structures. Measurements were taken for 0.5-11.5 months of baseline, chronic daily administration of chlorpromazine, and withdrawal. In most cases there was also a second cycle of drug administration and withdrawal. Although we observed dramatic, persistent increases in licking behavior, suggestive of tardive dyskinesia, consistent correlated patterns were not observed in somatosensory or substantia nigra evoked potentials, electroencephalogram, or spindling evoked in cortex by caudate stimulation.

Oral dyskinesia in rats following brain lesions and neuroleptic drug administration

After 10-12 weeks of chronic haloperidol administration rats with frontal cortex ablations or lesions induced by intracerebroventricular infection of 6-hydroxydopamine developed vacuous chewing behavior at a fairly stable frequency (bifrontal ablations had 15-20, 6-hydroxy-dopamine lesioned rats 7-12 chewing movements/min). This behavior persisted for 10 weeks after the last injection of haloperidol decanoate. However, rats with frontal cortex lesions developed a low rate of vacuous chewings (4-8 chewings/min) even without haloperidol administration. Bilateral intrastriatal injections of kainic acid in combination with chronic haloperidol administration did not cause chewing movements in excess of unlesioned haloperidol-treated controls. Pharmacological tests of this animal model for tardive dyskinesia (TD) revealed similarities to human TD, but also differences. Dopamine agonists (apomorphine) and antagonists (haloperidol) both lowered chewing behavior analogous to reported effects on TD and so did gabaculine. The cholinergic drugs physostigmine and pilocarpine, however, increased chewing in rats, while anticholinergics (atropine) reduced it, in contrast to reported effects on human TD.