Persistent alterations in dendrites, spines, and dynorphinergic synapses in the nucleus accumbens shell of rats with neuroleptic-induced dyskinesias

Prescription of Anticholinergics in Tardive Syndromes: A "Dual Center" Survey among Psychiatrists

Methods

We assessed the attitude of two groups of psychiatrists (practicing in Italy and Thailand) towards the prescription of anticholinergics by a short online survey consisting of four questions. A total of one hundred questionnaires were sent out (50 in Italy and 50 in Thailand), and 42 psychiatrists responded to the survey.

Results

When comparing the two cohorts, the difference, both for age and years of practice, was statistically significant (p < 0.00001 and p < 0.0001, respectively), with Thai psychiatrists being younger and with less time in practice as specialists. The results from the survey showed that the prescription of anticholinergic drugs at the beginning of the antipsychotic treatment was used by 5 psychiatrists (20.0%) of the Italian cohort and by 1 (5.9%) of the Thai cohort. Regarding the Italian psychiatrists who did not prescribe anticholinergics concomitantly with neuroleptics, we found that 5 (25.0%) of them had prescribed anticholinergics in the past but had abandoned this practice, while 15 (93.7%) of the Thai psychiatrists who did not prescribe anticholinergics at the moment of the survey answered that they had prescribed these drugs in the past.

Conclusion

According to this preliminary survey, the practice to use anticholinergics as a treatment for tardive syndromes is still relatively common, particularly in psychiatrists of the older generation, but seemingly in decline over the years.

The role of glutamate receptors and their interactions with dopamine and other neurotransmitters in the development of tardive dyskinesia: preclinical and clinical results

Tardive dyskinesia is a serious, disabling, movement disorder associated with the ongoing use of antipsychotic medication. Current evidence regarding the pathophysiology of tardive dyskinesia is mainly based on preclinical animal models and is still not completely understood. The leading preclinical hypothesis of tardive dyskinesia development includes dopaminergic imbalance in the direct and indirect pathways of the basal ganglia, cholinergic deficiency, serotonin receptor disturbances, neurotoxicity, oxidative stress, and changes in synaptic plasticity. Although, the role of the glutamatergic system has been confirmed in preclinical tardive dyskinesia models it seems to have been neglected in recent reviews. This review focuses on the role and interactions of glutamate receptors with dopamine, acetylcholine, and serotonin in the neuropathology of tardive dyskinesia development. Moreover, preclinical and clinical results of the differentiated effectiveness of N-methyl-D-aspartate (NMDA) receptor antagonists are discussed with a special focus on antagonists that bind with the GluN2B subunit of NMDA receptors. This review also presents new combinations of drugs that are worth considering in the treatment of tardive dyskinesia.

A unifying theory for the pathoetiologic mechanism of tardive dyskinesia

INTRODUCTION

Chronic treatment with dopamine D2 receptor antagonists has been proposed to lead to dopamine receptor supersensitivity. Frequently, this is conceptualized as upregulation or changes in the structure or function of the post-synaptic D2 receptor. However, the measured 1.4-fold increase in D2 receptor density and the lack of actual receptor supersensitivity are probably inadequate to explain outcomes such as tardive dyskinesia (TD) and dopamine supersensitivity psychosis.

HYPOTHESIS

Recent data suggest that TD may result from a combination of presynaptic, synaptic, and postsynaptic changes.

DISCUSSION

Presynaptic increase in dopamine release occurs when super-therapeutic blockade of postsynaptic D2 receptors results in excess synaptic unbound dopamine which ultimately ends up being reuptaken by the presynaptic neuron through the dopamine transporter. The increased availability of recycled dopamine results in higher vesicular dopamine concentrations. Since the quantity of neurotransmitter released (known as quanta) is determined by the number of presynaptic neurotransmitter vesicles, the increase in the number (concentration) of dopamine molecules in the vesicles results in a higher concentration of synaptic dopamine with successive depolarization events. Synaptic changes such as the appearance of perforated synapses which is an early step in new synapse formation have been shown in animal models of TD. Finally, postsynaptic increases in D2 receptor expression without demonstration of increased sensitivity or potency has been demonstrated.

CONCLUSION

TD likely develops due to changes across the synapse and terminology such as 'dopamine receptor supersensitivity' can be misleading. 'Synaptic upregulation' may be a more correct term.

Methylphenidate alters Akt-mTOR signaling in rat pheochromocytoma cells

The exponential increase in methylphenidate (MPH) prescriptions in recent years has worried researchers about its misuse among individuals who do not meet the full diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD) such as young children and students in search of cognitive improvement or for recreational reasons. The action of MPH is based mainly on inhibition of dopamine transporter, but the complete cellular effects are still unknown. Based upon prior studies, we attempted to determine whether the treatment with MPH (1μM) influences protein kinase B-mammalian target of rapamycin complex 1 signaling pathways (Akt-mTOR), including translation repressor protein (4E-BP1) and mitogen activated protein kinase (S6K), in rat pheochromocytoma cells (PC12), a well characterized cellular model, in a long or short term. MPH effects on the Akt substrates [cAMP response element-binding protein (CREB), forkhead box protein O1 (FoxO1), and glycogen synthase kinase 3 beta (GSK-3β)] were also evaluated. Whereas short term MPH treatment decreased the pAkt/Akt, pmTOR/mTOR and pS6K/S6K ratios, as well as pFoxO1 immunocontent in PC12 cells, long term treatment increased pAkt/Akt, pmTOR/mTOR and pGSK-3β/GSK-3β ratio. Phosphorylation levels of 4E-BP1 were decreased at 15 and 30 min and increased at 1 and 6 h by MPH. pCREB/CREB ratio was decreased. This study shows that the Akt-mTOR pathway, as well as other important Akt substrates which have been described as important regulators of protein synthesis, as well as being implicated in cellular survival, synaptic plasticity and memory consolidation, was affected by MPH in PC12 cells, representing an important step in exploring the MPH effects.

Antipsychotics activate mTORC1-dependent translation to enhance neuronal morphological complexity

Although antipsychotic drugs can reduce psychotic behavior within a few hours, full efficacy is not achieved for several weeks, implying that there may be rapid, short-term changes in neuronal function, which are consolidated into long-lasting changes. We showed that the antipsychotic drug haloperidol, a dopamine receptor type 2 (D₂R) antagonist, stimulated the kinase Akt to activate the mRNA translation pathway mediated by the mammalian target of rapamycin complex 1 (mTORC1). In primary striatal D₂R-positive neurons, haloperidol-mediated activation of mTORC1 resulted in increased phosphorylation of ribosomal protein S6 (S6) and eukaryotic translation initiation factor 4E-binding protein (4E-BP). Proteomic mass spectrometry revealed marked changes in the pattern of protein synthesis after acute exposure of cultured striatal neurons to haloperidol, including increased abundance of cytoskeletal proteins and proteins associated with translation machinery. These proteomic changes coincided with increased morphological complexity of neurons that was diminished by inhibition of downstream effectors of mTORC1, suggesting that mTORC1-dependent translation enhances neuronal complexity in response to haloperidol. In vivo, we observed rapid morphological changes with a concomitant increase in the abundance of cytoskeletal proteins in cortical neurons of haloperidol-injected mice. These results suggest a mechanism for both the acute and long-term actions of antipsychotics.

TLR-4-dependent and -independent mechanisms of fetal brain injury in the setting of preterm birth

In this study, we sought to assess how essential activation of toll-like receptor 4 (TLR-4) is to fetal brain injury from intrauterine inflammation. Both wild-type and TLR-4 mutant fetal central nervous system cells were exposed to inflammation using lipopolysaccharide in vivo or in vitro. Inflammation could not induce neuronal injury in the absence of glial cells, in either wild-type or TLR-4 mutant neurons. However, injured neurons could induce injury in other neurons regardless of TLR-4 competency. Our results indicate that initiation of neuronal injury is a TLR-4-dependent event, while propagation is a TLR-4-independent event.

Parallels between behavioral and neurochemical variability in the rat vacuous chewing movement model of tardive dyskinesia

The widely accepted rat vacuous chewing movement model for tardive dyskinesia could be more fully mined through greater focus on individual variability in vulnerability to this neuroleptic-induced behavior. We have examined parallels between behavioral and neurobiological variability within a cohort in order to evaluate the role that neurobiological factors might play in determining susceptibility to tardive dyskinesia. Inter-observer reliability and individual consistency across time, in both spontaneous and neuroleptic-induced vacuous chewing movements, were empirically demonstrated. While this behavior increased across 8 months of observation in both vehicle controls and haloperidol-treated rats, pre-treatment baselines were predictive of final levels across individuals only in the vehicle control group, not the haloperidol-treated group. Haloperidol-induced elevations in neostriatal D2 and GAD(67) mRNA were not correlated with individual variability in haloperidol-induced vacuous chewing movements. Ambient noise during the observations was found to exacerbate chronic haloperidol-induced, but not spontaneous vacuous chewing movements. Significant correlations were found among the haloperidol-treated rats between nigral and tegmental GAD(67) and tegmental α7 mRNA levels, measured by in situ hybridization histochemistry, and vacuous chewing movements, specifically in the noisy conditions. Variability in these secondary responses to primary striatal dopamine and GABA perturbations may play a role in determining vulnerability to vacuous chewing movements, and by analogy, tardive dyskinesia. Both the differential predictive value of baseline vacuous chewing movements and the differential effect of noise, between controls and haloperidol-treated rats, add to evidence that haloperidol-induced vacuous chewing movements are regulated, in part, by different mechanisms than those mediating spontaneous vacuous chewing movements.

Anatomy of Graft-induced Dyskinesias: Circuit Remodeling in the Parkinsonian Striatum

The goal of researchers and clinicians interested in re-instituting cell based therapies for PD is to develop an effective and safe surgical approach to replace dopamine (DA) in individuals suffering from Parkinson's disease (PD). Worldwide clinical trials involving transplantation of embryonic DA neurons into individuals with PD have been discontinued because of the often devastating post-surgical side-effect known as graft-induced dyskinesia (GID). There have been many review articles published in recent years on this subject. There has been a tendency to promote single factors in the cause of GID. In this review, we contrast the pros and cons of multiple factors that have been suggested from clinical and/or preclinical observations, as well as novel factors not yet studied that may be involved with GID. It is our intention to provide a platform that might be instrumental in examining how individual factors that correlate with GID and/or striatal pathology might interact to give rise to dysfunctional circuit remodeling and aberrant motor output.

Effect of chronic L-dopa or melatonin treatments after dopamine deafferentation in rats: dyskinesia, motor performance, and cytological analysis

The present study examines the ability of melatonin to protect striatal dopaminergic loss induced by 6-OHDA in a rat model of Parkinson's disease, comparing the results with L-DOPA-treated rats. The drugs were administered orally daily for a month, their therapeutic or dyskinetic effects were assessed by means of abnormal involuntary movements (AIMs) and stepping ability. At the cellular level, the response was evaluated using tyrosine hydroxylase immunoreactivity and striatal ultrastructural changes to compare between L-DOPA-induced AIMs and Melatonin-treated rats. Our findings demonstrated that chronic oral administration of Melatonin improved the alterations caused by the neurotoxin 6-OHDA. Melatonin-treated animals perform better in the motor tasks and had no dyskinetic alterations compared to L-DOPA-treated group. At the cellular level, we found that Melatonin-treated rats showed more TH-positive neurons and their striatal ultrastructure was well preserved. Thus, Melatonin is a useful treatment to delay the cellular and behavioral alterations observed in Parkinson's disease.

Dopamine D1 and N-methyl-D-aspartate receptors and extracellular signal-regulated kinase mediate neuronal morphological changes induced by repeated cocaine administration

The development of drug addiction involves persistent cellular and molecular changes in the CNS. The brain dopamine and glutamate systems play key roles in mediating drug-induced neuroadaptation. Changes in dendritic morphology in medium spiny neurons (MSNs) in the nucleus accumbens (NAc) and caudate putamen (CPu) accompany drug-induced enduring behavioral and molecular changes. We have investigated the potential involvement of dopamine D1 and D2 receptors, the N-methyl-D-aspartate (NMDA) receptor, and the extracellular signal-regulated kinase (ERK) in dendritic morphological changes induced by repeated cocaine administration. We show that either a genetic mutation or pharmacological blockade of dopamine D1 receptors attenuated cocaine-induced changes in both dendritic branching and spine density of MSNs in the shell of the NAc and CPu. In contrast, antagonism of dopamine D2 receptors had no obvious effect on changes in dendritic branching but had a partial effect on changes in spine density of MSNs in these brain regions following repeated cocaine injections. Pharmacological inhibition of either NMDA receptors or ERK attenuated cocaine-induced changes in both dendritic branching and spine density of MSNs in the shell of the NAc and CPu. These results suggest that dopamine D1 and NMDA receptors and ERK contribute significantly to neuronal morphological changes induced by repeated exposure to cocaine.

Impact of dendritic spine preservation in medium spiny neurons on dopamine graft efficacy and the expression of dyskinesias in parkinsonian rats

Dopamine deficiency associated with Parkinson's disease (PD) results in numerous changes in striatal transmitter function and neuron morphology. Specifically, there is marked atrophy of dendrites and dendritic spines on striatal medium spiny neurons (MSN), primary targets of inputs from nigral dopamine and cortical glutamate neurons, in advanced PD and rodent models of severe dopamine depletion. Dendritic spine loss occurs via dysregulation of intraspine Cav1.3 L-type Ca(2+)channels and can be prevented, in animal models, by administration of the calcium channel antagonist, nimodipine. The impact of MSN dendritic spine loss in the parkinsonian striatum on dopamine neuron graft therapy remains unexamined. Using unilaterally parkinsonian Sprague-Dawley rats, we tested the hypothesis that MSN dendritic spine preservation through administration of nimodipine would result in improved therapeutic benefit and diminished graft-induced behavioral abnormalities in rats grafted with embryonic ventral midbrain cells. Analysis of rotational asymmetry and spontaneous forelimb use in the cylinder task found no significant effect of dendritic spine preservation in grafted rats. However, analyses of vibrissae-induced forelimb use, levodopa-induced dyskinesias and graft-induced dyskinesias showed significant improvement in rats with dopamine grafts associated with preserved striatal dendritic spine density. Nimodipine treatment in this model did not impact dopamine graft survival but allowed for increased graft reinnervation of striatum. Taken together, these results demonstrate that even with grafting suboptimal numbers of cells, maintaining normal spine density on target MSNs results in overall superior behavioral efficacy of dopamine grafts.

Effect of levodopa priming on dopamine neuron transplant efficacy and induction of abnormal involuntary movements in parkinsonian rats

Clinical trials of neural grafting for Parkinson's disease (PD) have produced variable, but overall disappointing, results. One particular disappointment has been the development of aberrant motor complications following dopamine (DA) neuron grafting. Despite a lack of consistent benefit, the utility of dopamine neuron replacement remains supported by clinical and basic data. In a continued effort to elucidate factors that might improve this therapy, we used a parkinsonian rat model to examine whether pregraft chronic levodopa affected graft efficacy and/or graft-induced dyskinesia (GID) induction. Indeed, all grafted PD patients to date have had a pregraft history of long-term levodopa. It is well established that long-term levodopa results in a plethora of long-lasting neurochemical alterations and genomic changes indicative of altered structural and synaptic plasticity. Thus, therapeutic dopamine terminal replacement in a striatal environment complicated by such changes could be expected to lead to abnormal or inappropriate connections between graft and host brain and to contribute to suboptimal efficacy and/or postgraft GID behaviors. To investigate the effect of pregraft levodopa, one group of parkinsonian rats received levodopa for 4 weeks prior to grafting. A second levodopa-naïve group was grafted, and the grafts were allowed to mature for 9 weeks prior to introducing chronic levodopa. We report here that, in parkinsonian rats, preexposure to chronic levodopa significantly reduces behavioral and neurochemical efficacy of embryonic dopamine grafts. Furthermore, dopamine terminal replacement prior to introduction of chronic levodopa is highly effective at preventing development of levodopa-induced dyskinesias, and GID-like behaviors occur regardless of pregraft levodopa status.

The synaptic impact of the host immune response in a parkinsonian allograft rat model: Influence on graft-derived aberrant behaviors

Graft-induced dyskinesias (GIDs), side-effects found in clinical grafting trials for Parkinson's disease (PD), may be associated with the withdrawal of immunosuppression. The goal of this study was to determine the role of the immune response in GIDs. We examined levodopa-induced dyskinesias (LIDs), GID-like behaviors, and synaptic ultrastructure in levodopa-treated, grafted, parkinsonian rats with mild (sham), moderate (allografts) or high (allografts plus peripheral spleen cell injections) immune activation. Grafts attenuated amphetamine-induced rotations and LIDs, but two abnormal motor syndromes (tapping stereotypy, litter retrieval/chewing) emerged and increased with escalating immune activation. Immunohistochemical analyses confirmed immune activation and graft survival. Ultrastructural analyses showed increases in tyrosine hydroxylase-positive (TH+) axo-dendritic synapses, TH+ asymmetric specializations, and non-TH+ perforated synapses in grafted, compared to intact, striata. These features were exacerbated in rats with the highest immune activation and correlated statistically with GID-like behaviors, suggesting that immune-mediated aberrant synaptology may contribute to graft-induced aberrant behaviors.

The structural basis for mapping behavior onto the ventral striatum and its subdivisions

The striatum can be divided into dorsal (caudate-putamen) and ventral parts. In the ventral division, the nucleus accumbens, which subserves adaptive and goal-directed behaviors, is further subdivided into shell and core. Accumbal neurons show different types of experience-dependent plasticity: those in the core seem to discriminate the motivational value of conditioned stimuli, features that rely on the integration of information and enhanced synaptic plasticity at the many spines on these cells, whereas shell neurons seem to be involved with the release of predetermined behavior patterns in relation to unconditioned stimuli, and the behavioral consequences of repeated administration of addictive drugs. In the core, the principal neurons are medium sized and densely spiny, but in the medial shell, these same neurons are much smaller and their dendrites, significantly less spiny, suggesting that morphological differences could mediate unique neuroadaptations associated with each region. This review is focused on evaluating the structural differences in nucleus accumbens core and shell neurons and discusses how such different morphologies could underlie distinguishable behavioral processes.

Dendritic distributions of dopamine D1 receptors in the rat nucleus accumbens are synergistically affected by startle-evoking auditory stimulation and apomorphine

Prepulse inhibition of the startle response to auditory stimulation (AS) is a measure of sensorimotor gating that is disrupted by the dopamine D1/D2 receptor agonist, apomorphine. The apomorphine effect on prepulse inhibition is ascribed in part to altered synaptic transmission in the limbic-associated shell and motor-associated core subregions of the nucleus accumbens (Acb). We used electron microscopic immunolabeling of dopamine D1 receptors (D1Rs) in the Acb shell and core to test the hypothesis that region-specific redistribution of D1Rs is a short-term consequence of AS and/or apomorphine administration. Thus, comparisons were made in the Acb of rats killed 1 h after receiving a single s.c. injection of vehicle (VEH) or apomorphine (APO) alone or in combination with startle-evoking AS (VEH+AS, APO+AS). In both regions of all animals, the D1R immunoreactivity was present in somata and large, as well as small, presumably more distal dendrites and dendritic spines. In the Acb shell, compared with the VEH+AS group, the APO+AS group had more spines containing D1R immunogold particles, and these particles were more prevalent on the plasma membranes. This suggests movement of D1Rs from distal dendrites to the plasma membrane of dendritic spines. Small- and medium-sized dendrites also showed a higher plasmalemmal density of D1R in the Acb shell of the APO+AS group compared with the APO group. In the Acb core, the APO+AS group had a higher plasmalemmal density of D1R in medium-sized dendrites compared with the APO or VEH+AS group. Also in the Acb core, D1R-labeled dendrites were significantly smaller in the VEH+AS group compared with all other groups. These results suggest that alerting stimuli and apomorphine synergistically affect distributions of D1R in Acb shell and core. Thus adaptations in D1R distribution may contribute to sensorimotor gating deficits that can be induced acutely by apomorphine or develop over time in schizophrenia.

Persistent and reversible morphine withdrawal-induced morphological changes in the nucleus accumbens

Morphine withdrawal produces a hypofunction of mesencephalic dopamine (DA) neurons which impinge upon medium spiny neurons (MSN) of the forebrain. After chronic treatment rats were either spontaneously or pharmacologically withdrawn from chronic morphine: under these two distinct conditions we studied the effects of withdrawal on spine density of MSN of the core and shell of the nucleus accumbens (NAcc) at various times (1-3-7-14 days). MSN were stained with the Golgi-Cox procedure and analyzed by a confocal laser-scanning microscope. Our analysis shows that both spontaneous and naloxone-induced withdrawal produces a long-lasting but reversible reduction in spines' density in shell MSN, as compared with core MSN. This effect is selectively localized at the level of second-order dendritic trunks and persists up to 14 days when spine density was found within control (pretreatment) values. By contrast, spine density counts of NAcc MSN from rats chronically treated with morphine, did not reveal any change over time. Collectively, the results of the present article suggest that spontaneous and pharmacologically precipitated withdrawal, but not chronic morphine, persistently but reversibly reduce spines' density under a condition of reduced mesolimbic DA transmission, and the reduction of spines' density in second-order dendritic trunks is selectively segregated in the MSN of the shell of the NAcc. Morphine withdrawal dramatically, lastingly, and reversibly reduces spine density, selectively in second-order dendritic trunks of NAcc shell MSN, thereby further impoverishing the already abated DA transmission. These results may be relevant in the most harmful consequences of drug addiction such as craving and loss of control over intake and are in line with recent views suggesting the hypodopaminergic state as a cardinal feature of drug dependence.

Differential modulation of a 40 kDa catecholamine regulated protein in the core and shell subcompartments of the nucleus accumbens following chronic quinpirole and haloperidol administration in the rat

Past reports have shown dopamine (DA) D2/D3 receptor agonist quinpirole (QNP) and the DA D2 receptor antagonist, haloperidol (HAL) display a significant increase in expression of catecholamine regulated protein (CRP40) in the nucleus accumbens (NAcc) and the striatum, respectively. The present study investigated the in vivo effects of QNP and HAL on CRP40 protein levels within the core and shell subcompartments of the NAcc. As significant homology exists between CRP40 and Hsp70/Hsc70, parallel studies with inducible Hsp70 and constitutive Hsc70 were conducted to establish the specificity with respect to QNP on Hsp70 and CRP40. Results demonstrated that CRP40 protein was significantly expressed in the shell relative to the core region of NAcc following chronic QNP (+16.28%+/-0.42%, P<0.05) and CRP40 protein was significantly expressed in the core vs. the shell following chronic HAL (+36.02%+/-0.75%, P<0.05). There was no significant change in Hsp70 protein levels following chronic QNP or HAL administration. The results demonstrated selective modulation of CRP40 within NAcc by QNP and HAL treatment, without affecting Hsp70.

Targeting dopamine D2 and cannabinoid-1 (CB1) receptors in rat nucleus accumbens

The nucleus accumbens (Acb) shell and core are essential components of neural circuitry mediating the reward and motor effects produced by activation of dopamine D2 or cannabinoid-1 (CB1) receptors. D2 receptors can form heterodimeric complexes with cannabinoid-1 (CB1) receptors and are also involved in control of the availability of both dopamine and endocannabinoids. Thus, the subcellular locations of D2 and CB1 receptors with respect to each other are implicit to their physiological actions in the Acb. We used electron microscopic immunocytochemistry to determine these locations in the Acb shell and core of rat brain. In each region, many neuronal profiles showed endomembrane and plasmalemmal distributions of one or both receptors. Approximately one-third of the labeled profiles were somata and dendrites, some of which showed overlapping subcellular distributions of D2 and CB1 immunoreactivities. The remaining labeled profiles were small axons and axon terminals containing CB1 and/or D2 receptors. Of the labeled terminals forming recognizable synapses, approximately 20% of those containing CB1 receptors contacted D2-labeled dendrites, while conversely, almost 15% of those containing D2 receptors contacted CB1-labeled dendrites. These results provide the first ultrastructural evidence that D2 and CB1 receptors in the Acb shell and core have subcellular distributions supporting both intracellular associations and local involvement of D2 receptors in making available endocannabinoids that are active on CB1 receptors in synaptic neurons. These distributions have direct relevance to the rewarding and euphoric as well as motor effects produced by marijuana and by addictive drugs enhancing dopamine levels in the Acb.

The effect of chronic administration of sarizotan, 5-HT1A agonist/D3/D4 ligand, on haloperidol-induced repetitive jaw movements in rat model of tardive dyskinesia

Dyskinesia is the most troublesome side effect in long-term treatment of both Parkinson's disease (PD) and schizophrenia. The 5-HT1A agonist and D3/D4 ligand sarizotan [Bartoszyk, G.D., van Amsterdam, C., Greiner, H.E., Rautenberg, W., Russ, H., Seyfried, C.A., 2004. Sarizotan, a serotonin 5-HT1A receptor agonist and dopamine receptor ligand. 1. Neurochemical profile. J. Neural Transm. 111, 113-126.] is in clinical development for the treatment of PD-associated dyskinesia. Because 5-HT1A agonists are known to counteract antipsychotic-induced motor side effects, sarizotan was investigated for its effects in two rat models of tardive dyskinesia (TD). The acute administration of sarizotan (0.17-13.5 mg/kg i.p.) reduced episodes of SKF 38393-induced repetitive jaw movements (RJM) in rats with a maximal effect at 1.5 mg/kg. In a chronic study, sarizotan (0.04-9 mg/kg/day), administered in the drinking water for 7 weeks during withdrawal from chronic haloperidol treatment (1.5 mg/kg/day), dose-dependently reversed haloperidol-induced RJM, significant at the doses of 1.5 and 9 mg/kg. Agonism at 5-HT1A receptors may be mediating the inhibitory effect of sarizotan on RJM in rat models of tardive dyskinesia.

Antipsychotic-associated neuronal changes in the brain: toxic, therapeutic, or irrelevant to the long-term outcome of schizophrenia?

The increasingly wide-spread use of antipsychotics in both adults and children calls for a detailed examination of antipsychotic-associated neuronal changes in the brain, and whether these changes are toxic, therapeutic, or perhaps irrelevant to the outcome of major psychiatric disorders, especially schizophrenia. In this review we will examine the extensive evidence demonstrating both acute and longer-term antipsychotic-associated neurotoxicity and neuroplasticity, as well as the more specific cellular changes that appear to underlie these phenomena. These include changes in proteins affecting cell survival, impairment of the mitochondrial respiratory chain, increases in DNA fragmentation, injury to dendritic microtubules, increases in dopamine-generated reactive oxygen species, changes in cell morphology, and rapid induction of apoptosis. We shall also examine the correlation between these changes and alterations in gross brain structure. There appears to be a disjunction between the widespread cellular and gross structural brain changes in schizophrenia, and the duration of illness, expression of symptoms, and response to treatment. We shall explore possible explanations for this apparent paradox.

Morphine withdrawal-induced morphological changes in the nucleus accumbens

Morphine withdrawal produces a hypofunction of mesencephalic dopamine neurons that impinge upon medium spiny neurons (MSN) of the forebrain. After chronic treatment (from 20 to 140 mg/kg of morphine twice a day over 14 days at escalating doses) rats were withdrawn from chronic morphine spontaneously and pharmacologically. In these two distinct conditions we studied the effects of withdrawal on the morphology of MSN of the core and shell of the nucleus accumbens (Nacc). MSN were stained with the Golgi-Cox procedure and analysed by a confocal laser-scanning microscope (CLSM). Our analysis shows that, shell and core MSN differed significantly for perikarya size and spine density, and the various morphine treatments did not affect the perikarya morphometry. Both spontaneous and naloxone-induced withdrawal produced a similar reduction in spine density in MS shell neurons, as compared with MS core neurons. This effect is selectively localized at the level of second order dendritic trunks where afferents converge. By contrast, spine density counts of accumbens MSN from rats chronically treated with morphine, did not reveal any change. Collectively, the results of the present study are twofold: (i) spontaneous and pharmacologically precipitated withdrawal, but not chronic morphine per se, affects spine density of target structures of a reduced mesolimbic dopamine transmission, and (ii) the reduction of spine density in second order dendritic trunks is selectively segregated in the MSN of the shell of the Nacc. In conclusion, morphine withdrawal dramatically alters spine density, selectively in second order dendritic trunks of Nacc shell MSN, thereby further impoverishing the already abated dopamine (DA) transmission. This is in line with recent views suggesting the hypodopaminergic state as a cardinal feature of opioid dependence.

Alterations in striatal neuropeptide Y system activity of rats with haloperidol-induced behavioral supersensitivity

The study was conducted to determine whether the expression of behavioral supersensitivity induced by haloperidol (HAL) administered once daily (2 mg/kg i.p.) for 14 days is associated with the alterations in activity of neuropeptide Y (NPY) system in the striatum (caudate-putamen) and nucleus accumbens. Dopamine supersensitivity was tested by measurement of locomotor activity and stereotyped behavior after administration of the dopamine D2/D3 receptor agonist quinpirole (1 mg/kg i.p.) on day 1, 3 and 7 after HAL withdrawal. Neuropeptide Y-like immunoreactivity (NPY-LI) was determined in the striatum and nucleus accumbens isolated 6 h after quinpirole injection on day 1, 3 and 7 after the end of HAL treatment. NPY mRNA was quantified in these structures on day 7 after HAL withdrawal. HAL increased spontaneous locomotor activity and prevalence of rearing, grooming and head-down sniffing. At the same time, striatal NPY-LI increased progressively from the reduced level found on day 1 of haloperidol withdrawal. NPY mRNA remained unchanged. In saline-treated rats, quinpirole enhanced locomotion, rearing, and induced intense head-down sniffing and oral activity. These behavioral effects were accompanied by a decrease in striatal NPY-LI. NPY mRNA was slightly increased. HAL treatment altered response to quinpirole, namely it increased locomotion, intensified oral activity and reduced rearing and head-down sniffing. The second and the third quinpirole injection decreased NPY-LI levels. NPY mRNA was unchanged. In the nucleus accumbens, apart from a decrease in NPY-LI on day 1 after the last haloperidol dose, the level of NPY-LI and NPY mRNA in any experimental group did not differ from the control value. The presented results suggest that the alterations in the activity of the striatal but not nucleus accumbens NPY system contribute to adaptive changes induced by long-term haloperidol treatment and may be of significance to the motor hyperactivity induced by intermittent stimulation of postsynaptic dopamine D2 receptors.

Haloperidol treatment reverses behavioural and anatomical changes in cocaine-dependent mice

Abnormal dopamine (DA) transmission occurs in many pathological conditions, including drug addiction. Previously, we showed DA D2 receptor (D2R) activation results in pruning of the axonal arbour of DA neurones that innervate the dorsal striatum. Thus, we hypothesised that long-term D2R stimulation through drugs of addiction should cause arbour pruning of neurones that innervate the ventral striatum and thus reduce DA release and contribute to craving. If so, D2R blockade should return these arbours to normal size and may overcome craving. We show that long-term treatment with a D2R antagonist (haloperidol) reverses behavioural and anatomical effects of cocaine dependence in mice, including relapse. This change in arbour size reflects new synapse formation and our data suggest this must occur in the presence of increased DA activity to reverse cocaine-seeking behaviour. These findings hold significant implications for the understanding and treatment of cocaine addiction.

Decreased absolute amygdala volume in cocaine addicts

The amygdala is instrumental to a set of brain processes that lead to cocaine consumption, including those that mediate reward and drug craving. This study examined the volumes of the amygdala and hippocampus in cocaine-addicted subjects and matched healthy controls and determined that the amygdala but not the hippocampus was significantly reduced in volume. The right-left amygdala asymmetry in control subjects was absent in the cocaine addicts. Topological analysis of amygdala isosurfaces (population averages) revealed that the isosurface of the cocaine-dependent group undercut the anterior and superior surfaces of the control group, implicating a difference in the corticomedial and basolateral nuclei. In cocaine addicts, amygdala volume did not correlate with any measure of cocaine use. The amygdala symmetry coefficient did correlate with baseline but not cocaine-primed craving. These findings argue for a condition that predisposes the individual to cocaine dependence by affecting the amygdala, or a primary event early in the course of cocaine use.

Seizure suppression by gain-of-function escargot mutations

Suppressor mutations provide potentially powerful tools for examining mechanisms underlying neurological disorders and identifying novel targets for pharmacological intervention. Here we describe mutations that suppress seizures in a Drosophila model of human epilepsy. A screen utilizing the Drosophila easily shocked (eas) "epilepsy" mutant identified dominant suppressors of seizure sensitivity. Among several mutations identified, neuronal escargot (esg) reduced eas seizures almost 90%. The esg gene encodes a member of the snail family of transcription factors. Whereas esg is normally expressed in a limited number of neurons during a defined period of nervous system development, here normal esg was expressed in all neurons and throughout development. This greatly ameliorated both the electrophysiological and the behavioral epilepsy phenotypes of eas. Neuronal esg appears to act as a general seizure suppressor in the Drosophila epilepsy model as it reduces the susceptibility of several seizure-prone mutants. We observed that esg must be ectopically expressed during nervous system development to reduce seizure susceptibility in adults. Furthermore, induction of esg in a small subset of neurons (interneurons) will reduce seizure susceptibility. A combination of microarray and computational analyses revealed 100 genes that represent possible targets of neuronal esg. We anticipate that some of these genes may ultimately serve as targets for novel antiepileptic drugs.

Two cases of neuroleptic-induced prolonged extrapyramidal symptoms

Neuroleptic-induced extrapyramidal symptoms (EPS) are generally categorized as acute, withdrawal and tardive EPS. Here, we report two cases of a unique late-onset, long-lasting EPS (e.g., prolonged EPS); in those cases, EPS appeared a few months following initiation of haloperidol and lasted for a few months after significant reduction or complete withdrawal of neuroleptics. Case 1, a 41-year-old female, began to exhibit EPS such as bradykinesia, rigidity and parkinsonian gait 4 months after the haloperidol treatment. Her rigidity was ameliorated by a reduction of haloperidol; however, reduction of neuroleptics made it difficult for her to maintain a seated posture because of an imbalance of muscle tonus. Her EPS continued for 9 months even after haloperidol was switched to very low doses of thioridazine (10 mg/day). Case 2 is a 42-year-old female. She exhibited EPS including dysphagia and a difficulty in opening her mouth 3 months after the haloperidol treatment began. Her EPS lasted for 45 days, even after complete withdrawal of neuroleptics. The EPS observed in these two cases occurred even after prolactin levels became normal. "Prolonged EPS" is a unique subclass of neuroleptic-induced reversible EPS that might involve the coexistence of hypo- and hyper-dopaminergic transmission, especially in patients who show very low tolerance to neuroleptics.

Adenosine A2A-dopamine D2 receptor–receptor heteromers. Targets for neuro-psychiatric disorders

Emerging evidence shows that G protein-coupled receptors can form homo- and heteromers. These include adenosine A(2A) receptor-dopamine D(2) receptor heteromers, which are most probably localized in the dendritic spines of the striatopallidal GABAergic neurons, where they are in a position to modulate glutamatergic neurotransmission. The discovery of A(2A) receptor-dopamine D(2) receptor heteromers gives a frame for the well-known antagonistic interaction between both receptors, which is the bases for a new therapeutic approach for neuro-psychiatric disorders, such as Parkinson's disease and schizoprenia. The present review deals mainly with the biochemical and molecular aspects of A(2A) receptor-dopamine D(2) receptor interactions. Recent results at the molecular level show that A(2A) receptor-dopamine D(2) receptor heteromers represent the first example of epitope-epitope electrostatic interaction underlying receptor heteromerization. Most probably A(2A) receptor-D(2) receptor heteromerization is not static, but subject to a dynamic regulation, related to the phosphorylation dependence of the A(2A) receptor epitope and to the ability of the D(2) receptor epitope to bind different partners. Finding out the mechanisms involved in this dynamic regulation can have important implications for the treatment of basal ganglia disorders, schizophrenia and drug addiction.

Neuroleptic withdrawal in treatment-resistant patients with schizophrenia: tardive dyskinesia is not associated with supersensitive psychosis

The objective of this retrospective study was to determine whether tardive dyskinesia (TD) represents a risk factor for supersensitive psychosis (SS) by assessing the effect of medication withdrawal on ratings of psychopathology for 30 days following discontinuation of antipsychotic medication in patients with and without TD. The subjects were 101 treatment-resistant patients with schizophrenia who had been admitted to the inpatient service of Neuroscience Research Hospital (NRH), National Institute of Mental Health, between 1982 and 1994 to undergo studies involving discontinuation of antipsychotic medication. Patients were rated independently on a daily basis on the 22-item Psychiatric Symptom Assessment Scale (PSAS), an extended version of the Brief Psychiatric Rating Scale (BPRS). The overall frequency of TD was 35.6%. Tardive dyskinesia patients were older (p < 0.0006) and had suffered from schizophrenia for a longer time (p < 0.003) than No-TD patients. Repeated measure ANOVA revealed a "time" effect for all subgroups studied. The interaction TD x time, however, was not statistically significant for any of the clusters. Within-group analysis revealed significant differences against baseline for measures of positive symptoms, negative symptoms and abnormal involuntary movements in the No-TD group 3 and 4 weeks after antipsychotic withdrawal. In the TD group, however, the changes were observed only at 4 weeks following antipsychotic discontinuation in just two of the positive symptoms cluster. Between-group analyses revealed that, at baseline, the Mannerisms cluster (abnormal involuntary movements) was significantly higher in the TD group (p < 0.05). No significant differences were observed between any of the remaining clusters at baseline or at different times following drug withdrawal. In conclusion, the relationship between SS and TD could not be confirmed in a cohort of patients with treatment-resistant schizophrenia. In the present study, patients with no TD seemed to deteriorate faster than patients with TD in terms of psychopathology and abnormal involuntary movements. It is possible that both group of patients may undergo supersensitive receptor changes, and that these changes may be more pronounced but potentially reversible in the group without TD.

Changes in function and ultrastructure of striatal dopaminergic terminals that regenerate following partial lesions of the SNpc

Following partial substantia nigra lesions, remaining dopaminergic neurones sprout, returning terminal density in the dorsal striatum to normal by 16 weeks. This suggests regeneration and maintenance of terminal density is regulated to release appropriate levels of dopamine. This study examined the structure and function of these reinnervated terminals, defining characteristics of dopamine uptake and release, density and affinity of the dopamine transporter (DAT) and ultrastructural morphology of dopamine terminals in the reinnervated dorsal striatum. Finally, rotational behaviour of animals in response to amphetamine was examined 4 and 16 weeks after substantia nigra pars compacta (SNpc) lesions. Dopamine transport was markedly reduced 16 weeks after lesioning along with reduced density and affinity of DAT. Rate of dopamine release and peak concentration, measured electrochemically, was similar in lesioned and control animals, while clearance was prolonged after lesioning. Ultrastructurally, terminals after lesioning were morphologically distinct, having increased bouton size, vesicle number and mitochondria, and more proximal contacts on post-synaptic cells. After 4 weeks, tendency to rotate in response to amphetamine was proportional to lesion size. By 16 weeks, rotational behaviour returned to near normal in animals where lesions were less than 70%, although some animals demonstrated unusual rotational patterns at the beginning and end of the amphetamine effect. Together, these changes indicate that sprouted terminals are well compensated for dopamine release but that transport mechanisms are functionally impaired. We discuss these results in terms of implications for dyskinesia and other behavioural states.

Oral dyskinesias and histopathological alterations in substantia nigra after long-term haloperidol treatment of old rats

The pathophysiologic basis of tardive dyskinesia remains unclear, but several lines of evidence suggest that persistent neuronal changes in the basal ganglia produced by oxidative stress or glutamate toxicity may play a role, especially in the elderly. In the present study we examined whether histopathological alterations in substantia nigra are related to oral dyskinesia in a rodent model of tardive dyskinesia. Haloperidol decanoate (38 mg/kg/4 weeks) was administered to young (8 weeks) and old (38 weeks) rats for a total period of 28 weeks, and the development of vacuous chewing movements (VCM) was observed. Rats with high and low levels of VCM and saline-treated controls were analyzed for histopathological alterations. Reduced nerve cell number and atrophic neurons were prominent features in the substantia nigra of old rats with high levels of VCM. Some alterations were also present in the substantia nigra of the old rats with low levels of VCM and young rats with high VCM levels, but these were significantly less affected than the high VCM rats. These results show that the development of haloperidol-induced oral dyskinesias in old rats is associated with histopathological alterations in the substantia nigra. This suggests that nigral degeneration induced by neuroleptics may contribute to the development of persistent VCM in rats and possibly irreversible tardive dyskinesia in humans.

Blockade of nigral and pallidal opioid receptors suppresses vacuous chewing movements in a rodent model of tardive dyskinesia

Chronic neuroleptic treatment leads to the development of tardive dyskinesia in 20-30% of patients. While the pathogenesis of tardive dyskinesia remains elusive, altered opioid peptide function in striatal projection pathways of the basal ganglia has been implicated. Using a rodent model of vacuous chewing movements induced by chronic neuroleptic administration, we investigated regional involvement of opioid transmission in tardive dyskinesia. We examined the role of dynorphin in the direct striatonigral pathway by infusing nor-binaltorphimine, a selective kappa opioid receptor antagonist, into the substantia nigra pars reticulata. As well, infusions of naloxone (a non-specific opioid receptor antagonist), D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr amide (CTOP; a mu opioid receptor antagonist) or naltrindole (a delta opioid receptor antagonist) into the globus pallidus were used to establish the contribution of the striatopallidal pathway. Chronic fluphenazine treatment (25 mg/kg i.m. every 3 weeks for 18 weeks) resulted in a robust increase in vacuous chewing movements. Infusion of nor-binaltorphimine (5.0 nmol) into the substantia nigra pars reticulata significantly attenuated vacuous chewing movements. Infusion of naloxone (0.5 and 2.0 nmol) into the globus pallidus also significantly attenuated vacuous chewing. Infusion of naltrindole into the globus pallidus blocked vacuous chewing at all doses administered (0.5, 1.0, 2.0 nmol) while CTOP was only effective at the two higher doses. From these results we suggest that increases in dynorphin in the direct striatonigral pathway and enkephalin in the indirect striatopallidal pathway following chronic neuroleptic administration are both likely to contribute to tardive dyskinesia.

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.

Hippocampal and prefrontal cortical inputs monosynaptically converge with individual projection neurons of the nucleus accumbens

Afferents to the nucleus accumbens from different sources innervate specific areas of the central "core" and peripheral "shell" and are related to each other, at the light microscopical level, in an intricate overlapping and nonoverlapping way. This lack of homogeneity suggests that this region consists of circuits involving emsembles of neurons modulated by specific sets of convergent afferent inputs and abnormal regulation of such ensembles has been implicated in mental disorders. Early extracellular studies suggested that individual Acb neurons might respond to activation of afferents from more than one excitatory input: More recent studies of hippocampal and amygdalar or prefrontal cortical afferents suggest that hippocampal afferents gate the input from the prefrontal cortex or amygdala. Electrophysiological evidence for convergence of excitatory afferents in the Acb is strong and suggests that these pathways are monosynaptic. Nevertheless, this convergence has proved difficult to demonstrate anatomically as a result of the spatial distribution of the afferent inputs on the dendritic tree of the target neurons. To establish whether individual accumbens neurons receive monosynaptic input from pairs of afferents, one projection was labelled anterogradely with Phaseolus vulgaris leucoagglutinin and the second with biotinylated dextran amine (BDA) with Vector slate grey and 3,3'-diaminobenzidine tetrahydrochloride as the chromagens. Accumbens neurons possibly postsynaptic to these afferents, labelled by an in vivo focal injection of BDA, were examined using correlated light and electron microscopy to establish the proximal-distal distribution of labelled afferent synaptic inputs on their dendritic arbours. Individual cells were shown to receive monosynaptic afferent input from both ventral subiculum and prefrontal cortex, providing an anatomical framework for the hippocampal gating of other limbic inputs to the accumbens.

Acute administration of haloperidol induces apoptosis of neurones in the striatum and substantia nigra in the rat

Chronic administration of typical neuroleptics is associated with tardive dyskinesia in some patients. This dyskinetic syndrome has been associated with loss of GABAergic markers in the basal ganglia but the cause of these GABAergic depletions remains uncertain. Haloperidol, a commonly prescribed typical neuroleptic, is known to be toxic in vitro, possibly as a consequence of its conversion to pyridinium-based metabolites and potentially by raising glutamate-mediated transmission. We report here that the in vivo, acute administration of a large dose of haloperidol resulted in a microglial response indicative of neuronal damage. This was accompanied by an increase in the number of apoptotic cells in the striatum (especially in the dorsomedial caudate putamen) and in the substantia nigra pars reticulata. These apoptotic cells were characterised by the stereotaxic injection of a retrograde neuroanatomical tracer into the projection targets of the striatum and substantia nigra pars reticulata prior to the systemic injection of haloperidol. This procedure confirmed that the dying cells were neurones and demonstrated that within the striatum the majority were striatopallidal neurones though relatively high levels of apoptotic striatoentopeduncular neurones were also seen.The possibility that chronic administration of haloperidol could induce cumulative neuronal loss in the substantia nigra pars reticulata and thereby induce the pathological changes which lead to tardive dyskinesia is discussed.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.