NMDA receptor blockade attenuates the haloperidol induction of Fos protein in the dorsal but not the ventral striatum

Haloperidol-Induced Immediate Early Genes in Striatopallidal Neurons Requires the Converging Action of cAMP/PKA/DARPP-32 and mTOR Pathways

Antipsychotics share the common pharmacological feature of antagonizing the dopamine 2 receptor (D2R), which is abundant in the striatum and involved in both the therapeutic and side effects of this drug’s class. The pharmacological blockade of striatal D2R, by disinhibiting the D2R-containing medium-sized spiny neurons (MSNs), leads to a plethora of molecular, cellular and behavioral adaptations, which are central in the action of antipsychotics. Here, we focused on the cell type-specific (D2R-MSNs) regulation of some striatal immediate early genes (IEGs), such as cFos, Arc and Zif268. Taking advantage of transgenic mouse models, pharmacological approaches and immunofluorescence analyses, we found that haloperidol-induced IEGs in the striatum required the synergistic activation of A2a (adenosine) and NMDA (glutamate) receptors. At the intracellular signaling level, we found that the PKA/DARPP-32 and mTOR pathways synergistically cooperate to control the induction of IEGs by haloperidol. By confirming and further expanding previous observations, our results provide novel insights into the regulatory mechanisms underlying the molecular/cellular action of antipsychotics in the striatum.

Heart-type fatty acid binding protein regulates dopamine D2 receptor function in mouse brain

Fatty acid binding proteins (FABPs) are essential for energy production and long-chain polyunsaturated fatty acid-related signaling in the brain and other tissues. Of various FABPs, heart-type fatty acid binding protein (H-FABP, FABP3) is highly expressed in neurons of mature brain and plays a role in arachidonic acid incorporation into brain and heart cells. However, the precise function of H-FABP in brain remains unclear. We previously demonstrated that H-FABP is associated with the dopamine D(2) receptor long isoform (D2LR) in vitro. Here, we confirm that H-FABP binds to dopamine D(2) receptor (D2R) in brain extracts and colocalizes immunohistochemically with D2R in the dorsal striatum. We show that H-FABP is highly expressed in acetylcholinergic interneurons and terminals of glutamatergic neurons in the dorsal striatum of mouse brain but absent in dopamine neuron terminals and spines in the same region. H-FABP knock-out (KO) mice showed lower responsiveness to methamphetamine-induced sensitization and enhanced haloperidol-induced catalepsy compared with wild-type mice, indicative of D2R dysfunction. Consistent with the latter, aberrant increased acetylcholine (ACh) release and depolarization-induced glutamate (Glu) release were observed in the dorsal striatum of H-FABP KO mice. Furthermore, phosphorylation of CaMKII (Ca(2+)/calmodulin-dependent protein kinase II) and ERK (extracellular signal-regulated kinase) was significantly increased in the dorsal striatum. We confirmed elevated ERK phosphorylation following quinpirole-mediated D2R stimulation in H-FABP-overexpressing SHSY-5Y human neuroblastoma cells. Together, H-FABP is highly expressed in ACh interneurons and glutamatergic terminals, thereby regulating dopamine D2R function in the striatum.

Repeated amphetamine administration induces Fos in prefrontal cortical neurons that project to the lateral hypothalamus but not the nucleus accumbens or basolateral amygdala

RATIONALE

The development of sensitization to amphetamine (AMPH) is dependent on increases in excitatory outflow from the medial prefrontal cortex (mPFC) to subcortical centers. These projections are clearly important for the progressive enhancement of the behavioral response during drug administration that persists through withdrawal.

OBJECTIVES

The objective of this study was to identify the mPFC subcortical pathway(s) activated by a sensitizing regimen of AMPH.

MATERIALS AND METHODS

Using retrograde labeling techniques, Fos activation was evaluated in the predominant projection pathways of the mPFC of sensitized rats after a challenge injection of AMPH.

RESULTS

There was a significant increase in Fos-immunoreactive cells in the mPFC, nucleus accumbens (NAc), basolateral amygdala (BLA), and lateral hypothalamus (LH) of rats treated repeatedly with AMPH when compared to vehicle-treated controls. The mPFC pyramidal neurons that project to the LH but not the NAc or BLA show a significant induction of Fos after repeated AMPH treatment. In addition, we found a dramatic increase in Fos-activated orexin neurons.

CONCLUSIONS

The LH, a region implicated in natural and drug reward processes, may play a role in the development and persistence of sensitization to repeated AMPH through its connections with the mPFC and possibly through its orexin neurons.

The neural substrates of amphetamine conditioned place preference: implications for the formation of conditioned stimulus-reward associations

Associations formed between conditioned stimuli and drug reward are major contributors in human drug addiction. To better understand the brain changes that accompany this process, we used immunohistochemistry for c-Fos (a neuronal activity marker), synaptophysin (a marker for synaptogenesis) and tyrosine kinase B receptor (a neurotrophic factor receptor that mediates synaptic plasticity) to investigate the neural substrates of amphetamine-induced conditioned place preference in rats. Conditioned place preference was induced by both 1.0 mg/kg and 0.3 mg/kg doses of amphetamine. Furthermore, amphetamine conditioning increased the density of c-Fos-immunoreactive cells and these cells were fully colocalized with the tyrosine kinase B receptor in the dentate gyrus, CA1 field and basolateral amygdala. Amphetamine conditioning increased the density of synaptophysin-immunoreactive varicosities in all brain regions studied, except the nucleus accumbens shell and dorsolateral striatum. The degree of conditioned place preference was highly correlated with c-Fos-immunoreactive cell density in the basolateral amygdala and with the density of synaptophysin-immunoreactive varicosities in all mesolimbic regions studied. The latter correlation was particularly impressive for the ventral pallidum and basolateral amygdala. The formation of conditioned stimulus-amphetamine reward associations is accompanied by tyrosine kinase B receptor expression in the basolateral amygdala and dentate gyrus, CA1 and CA3 fields of the hippocampus. These data therefore suggest that the formation of conditioned stimulus-reward associations requires, at least in part, activation of amygdalar-hippocampal circuits.

Fyn Is Required for Haloperidol-induced Catalepsy in Mice

Fyn-mediated tyrosine phosphorylation of N-methyl-D-aspartate (NMDA) receptor subunits has been implicated in various brain functions, including ethanol tolerance, learning, and seizure susceptibility. In this study, we explored the role of Fyn in haloperidol-induced catalepsy, an animal model of the extrapyramidal side effects of antipsychotics. Haloperidol induced catalepsy and muscle rigidity in the control mice, but these responses were significantly reduced in Fyn-deficient mice. Expression of the striatal dopamine D(2) receptor, the main site of haloperidol action, did not differ between the two genotypes. Fyn activation and enhanced tyrosine phosphorylation of the NMDA receptor NR2B subunit, as measured by Western blotting, were induced after haloperidol injection of the control mice, but both responses were significantly reduced in Fyn-deficient mice. Dopamine D(2) receptor blockade was shown to increase both NR2B phosphorylation and the NMDA-induced calcium responses in control cultured striatal neurons but not in Fyn-deficient neurons. Based on these findings, we proposed a new molecular mechanism underlying haloperidol-induced catalepsy, in which the dopamine D(2) receptor antagonist induces striatal Fyn activation and the subsequent tyrosine phosphorylation of NR2B alters striatal neuronal activity, thereby inducing the behavioral changes that are manifested as a cataleptic response.

Dopamine D2-like antagonists induce chromatin remodeling in striatal neurons through cyclic AMP-protein kinase A and NMDA receptor signaling

Antipsychotic drugs regulate gene transcription in striatal neurons by blocking dopamine D2-like receptors. Little is known about the underlying changes in chromatin structure, including covalent modifications at histone N-terminal tails that are epigenetic regulators of gene expression. We show that treatment with D2-like antagonists rapidly induces the phosphorylation of histone H3 at serine 10 and the acetylation of H3-lysine 14 in bulk chromatin from striatum and in nuclei of striatal neurons. We find that, in vivo, D2-like antagonist-induced H3 phospho-acetylation is inhibited by the NMDA receptor antagonist MK-801 and by the protein kinase A (PKA) inhibitor Rp-adenosine 3c',5c'-cyclic monophosphorothioate triethylammonium salt but increased by the PKA activator Sp-adenosine 3c',5c'-cyclic monophosphorothioate triethylammonium salt. Furthermore, in dissociated striatal cultures which lack midbrain and cortical pre-synaptic inputs, H3 phospho-acetylation was induced by glutamate, L-type Ca2+ channel agonists and activators of cAMP-dependent PKA but inhibited by NMDA receptor antagonists or PKA antagonists. The dual modification, H3pS10-acK14, was enriched at genomic sites with active transcription and showed the kinetics of the early response. Together, these results suggest that histone modifications and chromatin structure in striatal neurons are dynamically regulated by dopaminergic and glutamatergic inputs converging on the cellular level. Blockade of D2-like receptors induces H3 phospho-acetylation, H3pS10-acK14, through cAMP-dependent PKA, and post-synaptic NMDA receptor signaling.

Role of NMDA receptor subtypes in the induction of catalepsy and increase in Fos protein expression after administration of haloperidol

The increase of Fos expression in the striatum induced by haloperidol, an antagonist of the dopamine D2 receptor, might be related to the activation of glutamatergic neurotransmission, especially that of N-methyl-D-aspartate (NMDA) receptors. In this study, using behavioral and immunohistochemical techniques, we examined the effects of a noncompetitive NMDA antagonist, (+)-MK-801, and an NMDA receptor NR2B subunit antagonist, ifenprodil, on catalepsy, an extrapyramidal symptom; in this context, we also considered the expression of Fos protein in the forebrain after the administration of haloperidol. Catalepsy in mice, induced by the administration of haloperidol (1 mg/kg), was inhibited by pretreatment with (+)-MK-801 (0.2 mg/kg) or ifenprodil (10 mg/kg). Furthermore, pretreatment with (+)-MK-801 (0.2 mg/kg) significantly attenuated the induction of Fos-immunoreactive (IR) cells in the dorsomedial, dorsolateral, and ventrolateral striatum, but not in the shell region of the nucleus accumbens after the administration of haloperidol, whereas pretreatment with ifenprodil (10 mg/kg) significantly attenuated the induction of Fos-IR cells in all of these areas. It is known that ifenprodil binds sigma receptors and alpha-1 adrenergic receptors with high affinity. Pretreatment with the sigma receptor antagonist BD-1407 (3 mg/kg) or the alpha-1 adrenergic receptor antagonist prazosin (3 mg/kg) affected neither catalepsy nor the expression of Fos-IR cells after the administration of haloperidol. However, pretreatment with CP-101,606 (1 mg/kg), a selective antagonist for the NR2B subunit of the NMDA receptor, significantly attenuated catalepsy and the expression of Fos-IR cells in the forebrain after the administration of haloperidol. These results suggest that the NMDA receptor antagonists attenuated the induction of catalepsy and Fos-IR cells in forebrain after the administration of haloperidol. It was also suggested that haloperidol-induced expression of Fos-IR cells in the shell region of the nucleus accumbens might be differentially regulated by NMDA receptor subunits. Therefore, it appears that selective antagonists for the NR2B subunit of the NMDA receptor (e.g., CP-101,606) might be useful drugs for the treatment of extrapyramidal side effects (EPS) associated with the chronic use of typical antipsychotics such as haloperidol.

Short-term, D2 receptor blockade induces synaptic degeneration, reduces levels of tyrosine hydroxylase and brain-derived neurotrophic factor, and enhances D2-mediated firing in the ventral pallidum

Repeated treatments with neuroleptics are associated with biochemical and morphological alterations in forebrain neurons as well as an upregulation of D2-mediated changes in neuronal function. The present study evaluated the histological and physiological effects of three once-daily treatments with two chemically divergent neuroleptics, haloperidol (1 mg/kg i.p./day) and eticlopride (3 mg/kg i.p./day), measured in rats 24 h after the last injection. It was determined that this short-term antagonism of D2-like receptors induced fiber and terminal degeneration and significantly decreased tyrosine hydroxylase (TH) and brain-derived neurotrophic factor (BDNF) immunoreactivity in the ventral pallidum (VP), as determined by optical density measurements. While other forebrain regions demonstrated changes in TH and BDNF, the neurodegeneration profile was unique to the VP. This was accompanied by an enhancement in the efficacy of the D2 agonist quinpirole to increase spiking rate of VP neurons recorded in chloral hydrate-anesthetized rats. These data indicate that short-term treatments with D2 antagonists are sufficient to induce changes in the biochemical and morphological profiles uniquely within the VP. Moreover, the functional ramifications of these changes appear to include profound alterations in the way dopamine regulates neuronal activity in this region.

Time-dependent changes in gene expression profiles of midbrain dopamine neurons following haloperidol administration

Antipsychotic drugs require a treatment regimen of several weeks before clinical efficacy is achieved in patient populations. While the biochemical mechanisms underlying the delayed temporal profile remain unclear, molecular adaptations in specific neuroanatomical loci are likely involved. Haloperidol-induced changes in gene expression in various brain regions have been observed; however, alterations in distinct neuronal populations have remained elusive. The present study examined changes in gene expression profiles of ventral tegmental area (VTA) and substantia nigra (SN) tyrosine hydroxylase immunopositive neurons following 1, 10 or 21 days of haloperidol administration (0.5 mg/kg/day). Macroarrays were used to study the expression of receptors, signaling proteins, transcription factors and pre- and post-synaptic proteins. Data were analyzed using conventional statistical procedures as well as self-organizing maps (SOM) to elucidate conserved patterns of expression changes. Results show statistically significant haloperidol-induced and time-dependent alterations in 17 genes in the VTA and 25 genes in the SN, including glutamate and GABA receptor subunits, signaling proteins and transcription factors. SOMs revealed distinct patterns of gene expression changes in response to haloperidol. Understanding how gene expression is altered over a clinically relevant time course of haloperidol administration may provide insight into the development of antipsychotic efficacy as well as the underlying pathology of schizophrenia.

Bilateral lesions of the entorhinal cortex differentially modify haloperidol- and olanzapine-induced c-fos mRNA expression in the rat forebrain

Lesions of the entorhinal cortex are now an accepted model for mimicking some of the neuropathological aspects of schizophrenia, since evidence has accumulated for the presence of cytoarchitectonic abnormalities within this cortex in schizophrenic patients. The present study was undertaken to address the functional consequences of bilateral entorhinal cortex lesions on antipsychotic-induced c-fos expression. After a 15-day recovery period, the effect of a typical antipsychotic, haloperidol (1 mg/kg), on c-fos mRNA expression was compared with that of an atypical one, olanzapine (10 mg/kg), in both sham-lesioned and entorhinal cortex-lesioned rats. In sham-lesioned rats, both haloperidol and olanzapine induced c-fos expression in the caudal cingulate cortex, dorsomedial and dorsolateral caudate-putamen, nucleus accumbens core and shell and lateral septum. In addition, olanzapine, but not haloperidol, increased c-fos expression within the central amygdala. In entorhinal cortex-lesioned rats, haloperidol-induced c-fos expression was markedly reduced in most areas. In contrast, the olanzapine-induced c-fos expression was not altered in the nucleus accumbens shell and lateral septum of the lesioned rats. These findings reveal that entorhinal cortex lesions affect c-fos expression in a compound- and regional-dependent manner. Our results further emphasize the importance of the exploration of the mechanisms of action of antipsychotic drugs in the context of an associated cortical pathology.

Neurotensin: dual roles in psychostimulant and antipsychotic drug responses

Central administration of neurotensin (NT) results in a variety of neurobehavioral effects which, depending upon the administration site, resemble the effects of antipsychotic drugs (APDs) and psychostimulants. All clinically effective APDs exhibit significant affinities for dopamine D(2) receptors, supporting the hypothesis that an increase in dopaminergic tone contributes to schizophrenic symptoms. Psychostimulants increase extracellular dopamine (DA) levels and chronics administration can produce psychotic symptoms over time. APDs and psychostimulants induce Fos and NT expression in distinct striatal subregions, suggesting that changes in gene expression underlie some of their effects. To gain insight into the functions of NT, we analyzed APD and psychostimulant induction of Fos in NT knockout mice and rats pretreated with the NT antagonist SR 48692. In both NT knockout mice and rats pretreated with SR 48692, haloperidol-induced Fos expression was markedly attenuated in the dorsolateral striatum; amphetamine-induced Fos expression was reduced in the medial striatum. These results indicate that NT is required for the activation of specific subpopulations of striatal neurons in distinct striatal subregions in response to both APDs and psychostimulants. This review integrates these new findings with previous evidence implicating NT in both APD and psychostimulant responses.

Spatial and temporal profile of haloperidol-induced immediate-early gene expression and phosphoCREB binding in the dorsal and ventral striatum of amphetamine-sensitized rats

To determine if D(2) dopamine receptor-mediated nuclear signaling is altered during the development of amphetamine sensitization, we examined the expression of immediate-early gene (IEG) products, Fos, Jun, and Fos-related antigen (FRA), in both controls and amphetamine-sensitized rats after a challenge with the D(2) antagonist haloperidol. When chronic saline- or amphetamine (5 mg/kg, i.p. for 14 days)-treated rats were challenged with 2 mg/kg haloperidol at withdrawal day 3 (w3), more 35-kDa FRA was induced in the ventral striatum of the control group than in the amphetamine-treated rats. In contrast, more Jun and 35-kDa FRA were expressed in the ventral striatum of the amphetamine-treated group than in the controls when haloperidol was given at w10. Topographical analyses indicate that the decrease in FRA immunoreactive neuronal density in amphetamine-treated rats at w3 were located in the dorsolateral caudate/putamen and the nucleus accumbens shell and core subregions. Conversely, the increase in Jun-immunoreactive neurons in amphetamine-treated rats at w10 was observed in the dorsolateral caudate/putamen; in the case of the FRAs, the increase was observed in the nucleus accumbens shell. In addition, the time-dependent profile of IEG expression paralleled the activation of an upstream regulator, cAMP-response element binding protein, in the ventral striatum after haloperidol treatment. These neurochemical changes may be associated with behavioral plasticity, since amphetamine-treated rats displayed a lower amount of locomotor activity when exposed to a novel environment at w3, but had recovered at w10. Overall, the current study reveals that there is a distinct temporal and spatial profile of haloperidol-induced IEG expression and/or CREB phosphorylation in amphetamine-treated rats, suggesting that there is a critical transition between the early and late withdrawal periods.

FosB in rat striatum: normal regional distribution and enhanced expression after 6-month haloperidol administration

Subcortical motor nuclei show differential expression of FosB immediate early gene products and specifically deltaFosB after short (8, 19, or 21 days) chronic exposure to typical and atypical neuroleptics represented by haloperidol and clozapine, respectively. We quantitatively examined whether there are light microscopic regional variations in area density of FosB or the truncated deltaFosB in several motor-related nuclei of adult rats receiving vehicle or long chronic (6 months) administration of either depot haloperidol or clozapine in their drinking water. In control animals the dorsomedial and ventromedial caudate-putamen nucleus (CPN) had a significantly higher density of FosB-immunoreactive cells than the dorsolateral and ventrolateral regions. The nucleus accumbens (NAc) core also serving motor functions had a higher basal expression than the limbic shell region in control animals. The mediolateral gradient in area density of FosB-labeled cells was maintained in animals receiving either haloperidol or clozapine. In animals receiving haloperidol, but not clozapine, however, there was a regionally selective increase in the area density of only FosB-immunoreactive neurons in the dorsolateral and ventrolateral CPN and in both the core and shell of the NAc. Only the animals receiving chronic haloperidol showed vacuous chewing movements, the animal equivalent of tardive dyskinesia in humans. Our results suggest that, whereas the medial striatal neurons are activated under basal conditions, long chronic haloperidol induced FosB expression more exclusively in the lateral CPN and NAc core, implicating these regions specifically in the motor side effects of this drug.

Immunocytochemical characterization of catecholaminergic neurons in the rat striatum following dopamine-depleting lesions

It is possible either permanently or transiently to deplete the rat striatum of dopamine. Following such depletions, striatal neurons immunoreactive for tyrosine hydroxylase (TH), aromatic L-amino acid decarboxylase (AADC) or dopamine appear. The presence of dopamine-producing neurons in the striatum has relevance for the treatment of Parkinson's disease, but whether these catecholaminergic phenotypes all produce dopamine is unclear. In the present study we establish that after unilateral 6-hydroxydopamine lesions or methamphetamine administration, striatal TH-immunoreactive neurons differ in size, morphology and location from those that are immunopositive for AADC or dopamine. The TH-positive cells which were localized either to ventral parts of the striatum or to the central and dorsal areas of the caudate-putamen generally have the morphological features of projection neurons, whereas those containing AADC or dopamine were confined to subcallosal positions in the dorsal medial quadrant of the caudate-putamen and resemble small, local-circuit neurons. The fact that AADC-immunoreactive neurons overlap in size, morphology and location with the cells that produce dopamine suggests strongly that this population is dopaminergic. However, the simultaneous appearance of neurons that contain the TH enzyme but clearly do not make dopamine raises questions about the functional role of these cells and the cellular mechanisms responsible for their induction following striatal dopamine loss.