Olanzapine-induced Fos expression in the rat forebrain; cross-tolerance with haloperidol and clozapine

Extrapyramidal Side Effects with Chronic Atypical Antipsychotic Can Be Predicted by Labeling Pattern of FosB and phosphoThr34-DARPP-32 in Nucleus Accumbens

Extrapyramidal side effects (EPS) can be induced by neuroleptics that regulate the expression of transcription factor FosB and dopaminergic mediator DARPP-32 in the striatum. However, the long-term neurobiological changes in striatal projection neurons resulting from a cumulative dosage of typical and atypical antipsychotics are poorly understood. The present study aimed to determine the differential and long-lasting changes in FosB distribution and DARPP-32 phosphorylation in the striatum and nucleus accumbens (NAc) associated with chronic antipsychotic-induced EPS. Male C57Bl/6J mice received daily injections of Olanzapine (Olz, 15 mg/kg), Clozapine (Clz, 20 mg/kg), or Haloperidol (Hal, 1 mg/kg), for a period of 11 weeks with a 4-day withdrawal period before the last dosage. Catalepsy for detection of EPS, along with open-field and rotarod tests, were assessed as behavioral correlates of motor responses. Additionally, FosB and phosphorylated-DARPP-32 immunohistochemistry were examined in striatal regions after treatment. All antipsychotics produced catalepsy and reduced open-field exploration, such as impaired rota-rod performance after Olz and Hal. The washout period was critical for Clz-induced side effects reduction. Both Olz and Clz increased FosB in NAc Shell-region, and phosphoThr34-DARPP-32 in NAc. Only Clz reduced phosphoThr75-DARPP-32 in the dorsal striatum and showed FosB/phosphoThr34-Darpp-32-ir in the NAc Core region. This study provides evidence that atypical antipsychotics such as Olz and Clz also give rise to EPS effects frequently associated with a cumulative dosage of typical neuroleptics such as Hal. Nevertheless, FosB/phosphoThr34-Darpp-32-ir in the NAc Core region is associated with hypokinetic movements inhibition.

Combined In Silico, Ex Vivo, and In Vivo Assessment of L-17, a Thiadiazine Derivative with Putative Neuro- and Cardioprotective and Antidepressant Effects

Depression associated with poor general medical condition, such as post-stroke (PSD) or post-myocardial infarction (PMID) depression, is characterized by resistance to classical antidepressants. Special treatment strategies should thus be developed for these conditions. Our study aims to investigate the mechanism of action of 2-morpholino-5-phenyl-6H-1,3,4-thiadiazine, hydrobromide (L-17), a recently designed thiadiazine derivative with putative neuro- and cardioprotective and antidepressant-like effects, using combined in silico (for prediction of the molecular binding mechanisms), ex vivo (for assessment of the neural excitability using c-Fos immunocytochemistry), and in vivo (for direct examination of the neuronal excitability) methodological approaches. We found that the predicted binding affinities of L-17 to serotonin (5-HT) transporter (SERT) and 5-HT₃ and 5-HT_1A receptors are compatible with selective 5-HT serotonin reuptake inhibitors (SSRIs) and antagonists of 5-HT₃ and 5-HT_1A receptors, respectively. L-17 robustly increased c-Fos immunoreactivity in the amygdala and decreased it in the hippocampus. L-17 dose-dependently inhibited 5-HT neurons of the dorsal raphe nucleus; this inhibition was partially reversed by the 5-HT_1A antagonist WAY100135. We suggest that L-17 is a potent 5-HT reuptake inhibitor and partial antagonist of 5-HT₃ and 5-HT_1A receptors; the effects of L-17 on amygdaloid and hippocampal excitability might be mediated via 5-HT, and putatively mediate the antidepressant-like effects of this drug. Since L-17 also possesses neuro- and cardioprotective properties, it can be beneficial in PSD and PMID. Combined in silico predictions with ex vivo neurochemical and in vivo electrophysiological assessments might be a useful strategy for early assessment of the efficacy and neural mechanism of action of novel CNS drugs.

The use of melatonin to mitigate the adverse metabolic side effects of antipsychotics

Antipsychotic drugs are efficacious first-line treatments for many individuals diagnosed with a psychiatric illness. However, their adverse metabolic side-effect profile, which resembles the metabolic syndrome, represents a significant clinical problem that increases morbidity and limits treatment adherence. Moreover, the mechanisms involved in antipsychotic-induced adverse metabolic effects (AMEs) are unknown and mitigating strategies and interventions are limited. However, recent clinical trials show that nightly administration of exogenous melatonin may mitigate or even prevent antipsychotic-induced AMEs. This clinical evidence in combination with recent preclinical data implicate the circadian system in antipsychotic-induced AMEs and their mitigation. In this chapter, we provide an overview on the circadian system and its involvement in antipsychotic-induced AMEs, as well as the potential beneficial effect of nightly melatonin administration to mitigate them.

Exploring mechanisms of increased cardiovascular disease risk with antipsychotic medications: Risperidone alters the cardiac proteomic signature in mice

Atypical antipsychotic (AA) medications including risperidone (RIS) and olanzapine (OLAN) are FDA approved for the treatment of psychiatric disorders including schizophrenia, bipolar disorder and depression. Clinical side effects of AA medications include obesity, insulin resistance, dyslipidemia, hypertension and increased cardiovascular disease risk. Despite the known pharmacology of these AA medications, the mechanisms contributing to adverse metabolic side-effects are not well understood. To evaluate drug-associated effects on the heart, we assessed changes in the cardiac proteomic signature in mice administered for 4 weeks with clinically relevant exposure of RIS or OLAN. Using proteomic and gene enrichment analysis, we identified differentially expressed (DE) proteins in both RIS- and OLAN-treated mouse hearts (p < 0.05), including proteins comprising mitochondrial respiratory complex I and pathways involved in mitochondrial function and oxidative phosphorylation. A subset of DE proteins identified were further validated by both western blotting and quantitative real-time PCR. Histological evaluation of hearts indicated that AA-associated aberrant cardiac gene expression occurs prior to the onset of gross pathomorphological changes. Additionally, RIS treatment altered cardiac mitochondrial oxygen consumption and whole body energy expenditure. Our study provides insight into the mechanisms underlying increased patient risk for adverse cardiac outcomes with chronic treatment of AA medications.

Fos expression induced by olanzapine and risperidone in the central extended amygdala

The extended amygdala has been proposed to play an essential role in cognitive and affective processes and in neuropsychiatric disorders. In the present study, we examined the induction of Fos-like nuclei in the central amygdaloid nucleus (CeA), sublenticular extended amygdala (SLEA), interstitial nucleus of the posterior limb of the anterior commissure (IPAC), and bed nucleus of the stria terminalis (BSTL) of rodents to improve the knowledge regarding the pharmacological profile, therapeutic efficacy, and side-effects of olanzapine, an atypical antipsychotic drug and risperidone, a mixed atypical/typical antipsychotic drug in the rat brain. In addition, we evaluated the induction of Fos-like-nuclei in areas connected with these structures such as prefrontal cortex (PFCx), and nucleus accumbens shell, and in other important areas including the lateral septum and caudate-putamen that are involved in the therapeutic efficacy or side-effects of antipsychotic drugs. Fos-like-immunoreactivity induced by olanzapine and risperidone was compared with that by the atypical antipsychotic clozapine and typical antipsychotic haloperidol. Regarding the extended amygdala, and similarly to clozapine, olanzapine (5-10 mg/kg) and, with a lower efficacy, risperidone (1-3 mg/kg), induced Fos-like-nuclei in CeA, IPAC, SLEA, and BSTL. Both these drugs increased the induction of Fos-like-nuclei in PFCx, nucleus accumbens shell, lateral septum, and caudate-putamen. On the contrary, the increase of Fos-like-nuclei in the extended amygdala by haloperidol was restricted to IPAC only. These findings, consistent with the important role of extended amygdala in neuropsychiatric disorders characterized by affective disturbances, showed that olanzapine and risperidone, contrary to haloperidol, preferentially activated Fos-expression in these brain areas.

Cross-tolerance between nitric oxide synthase inhibition and atypical antipsychotics modify nicotinamide-adenine-dinucleotide phosphate-diaphorase activity in mouse lateral striatum

Previous research indicates that the subchronic administration of NG-nitro-L-arginine (L-NOARG) produces tolerance to haloperidol-induced catalepsy in Swiss mice. The present study aimed to further investigate whether intermittent subchronic systemic administration of L-NOARG induces tolerance to the cataleptic effects of haloperidol as well as olanzapine or clozapine (Clz) in C57Bl mice after subchronic administration for 5 consecutive days. Striatal FosB protein expression was measured in an attempt to gain further insights into striatal mechanisms in antipsychotic-induced extrapyramidal symptoms side effects. An nicotinamide-adenine-dinucleotide phosphate-diaphorase histochemical reaction was also used to investigate whether tolerance could induce changes in the number of nitric oxide synthase-active neurons. Subchronic administration of all antipsychotics produced catalepsy, but cross-tolerance was observed only between L-NOARG (15 mg/kg, intraperitoneally) and Clz (20 mg/kg, intraperitoneally). This cross-tolerance effect was accompanied by decreased FosB protein expression in the dorsal striatum and the nucleus accumbens shell region, and reduced icotinamide-adenine-dinucleotide phosphate-diaphorase activity in the dorsal and ventral lateral striatum. Overall, these results suggest that interference with the formation of nitric oxide, mainly in the dorsal and ventral lateral-striatal regions, appears to improve the cataleptic effects induced by antipsychotics acting as antagonists of low-affinity dopamine D2 receptor, such as Clz.

Spatial relationship between the c-Fos distribution and enkephalinergic, substance P, and tyrosine hydroxylase innervation fields after acute treatment with neuroleptics olanzapine, amisulpride, quetiapine, and aripiprazole in the rat septum

OBJECTIVE

The aim of the present study was to demonstrate the spatial relationship between the c-Fos immunoreactive cells elicited by an acute treatment with neuroleptics including amisulpride (AMI), olanzapine (OLA), quetiapine (QUE), and aripiprazole (ARI) and enkephalinergic (ENK), substance P (SP), and tyrosine hydroxylase (TH) innervation fields in the rat septum.

METHODS

Male Sprague Dawley rats received a single injection of OLA (5 mg), ARI (10 mg), AMI (20 mg), QUE (15 mg/kg/b.w.). Ninety min after antipsychotics administration, the animals were transcardially perfused with a fixative and the brains cryocut into serial coronal sections of 35 µm thickness. The sections were processed for c-Fos staining using an avidin-biotin-peroxidase complex and visualized by nickel intensified diaminobenzidine to reach black endproduct. Afterwards, the sections were exposed to ENK, SP, and TH antibodies and the reaction product visualized by biotin-labeled fluorescent AlexaFluor 564 dye. The data were evaluated from the sections either simultaneously illuminated with fluorescent and transmission microscope beams or after merging the separately illuminated sections in the Adobe Photoshop 7.0 software.

RESULTS

ENK, SP, and TH displayed characteristic spatial images formed by a dense accumulation of immunoreactive fibers and terminals on the both sides of the septum. A dense plexus of axons formed by ENK and SP immunopositive terminals were situated predominantly in the lateral, while TH ones more medial portion of the septum. QUE and AMI activated distinct amount of c-Fos expression in cells located within the SP-immunoreactive principal innervation field. The OLA effect on the c-Fos expression was very pronounced in the ventral TH-labeled principal innervation field including the space between the ENK field ventral portion and the dorsal margin of the accumbens nucleus shell. Generally, the occurrence of c-Fos cells in the ENK-immunoreactive principal innervation field, in comparison with the surrounding septal area, was less abundant after all of the four antipsychotics treatments.

CONCLUSION

The data of the present study indicate that ENK, SP, and TH innervation fields may influence separate populations of septal cells activated by AMI, OLA, QUE, and ARI and that each of these region-differently innervated cells may be associated with the functional heterogeneity of the individual lateral septal nuclei.

Olanzapine-induced early cardiovascular effects are mediated by the biological clock and prevented by melatonin

Second generation antipsychotics (SGA) are associated with adverse cardiometabolic side effects contributing to premature mortality in patients. While mechanisms mediating these cardiometabolic side effects remain poorly understood, three independent studies recently demonstrated that melatonin was protective against cardiometabolic risk in SGA-treated patients. As one of the main target areas of circulating melatonin in the brain is the suprachiasmatic nucleus (SCN), we hypothesized that the SCN is involved in SGA-induced early cardiovascular effects in Wistar rats. We evaluated the acute effects of olanzapine and melatonin in the biological clock, paraventricular nucleus and autonomic nervous system using immunohistochemistry, invasive cardiovascular measurements, and Western blot. Olanzapine induced c-Fos immunoreactivity in the SCN followed by the paraventricular nucleus and dorsal motor nucleus of the vagus indicating a potent induction of parasympathetic tone. The involvement of a SCN-parasympathetic neuronal pathway after olanzapine administration was further documented using cholera toxin-B retrograde tracing and vasoactive intestinal peptide immunohistochemistry. Olanzapine-induced decrease in blood pressure and heart rate confirmed this. Melatonin abolished olanzapine-induced SCN c-Fos immunoreactivity, including the parasympathetic pathway and cardiovascular effects while brain areas associated with olanzapine beneficial effects including the striatum, ventral tegmental area, and nucleus accumbens remained activated. In the SCN, olanzapine phosphorylated the GSK-3β, a regulator of clock activity, which melatonin prevented. Bilateral lesions of the SCN prevented the effects of olanzapine on parasympathetic activity. Collectively, results demonstrate the SCN as a key region mediating the early effects of olanzapine on cardiovascular function and show melatonin has opposing and potentially protective effects warranting additional investigation.

Melanin-concentrating hormone is necessary for olanzapine-inhibited locomotor activity in male mice

Olanzapine (OLZ), an atypical antipsychotic, can be effective in treating patients with restricting type anorexia nervosa who exercise excessively. Clinical improvements include weight gain and reduced pathological hyperactivity. However the neuronal populations and mechanisms underlying OLZ actions are not known. We studied the effects of OLZ on hyperactivity using male mice lacking the hypothalamic neuropeptide melanin-concentrating hormone (MCHKO) that are lean and hyperactive. We compared the in vivo effects of systemic or intra-accumbens nucleus (Acb) OLZ administration on locomotor activity in WT and MCHKO littermates. Acute systemic OLZ treatment in WT mice significantly reduced locomotor activity, an effect that is substantially attenuated in MCHKO mice. Furthermore, OLZ infusion directly into the Acb of WT mice reduced locomotor activity, but not in MCHKO mice. To identify contributing neuronal mechanisms, we assessed the effect of OLZ treatment on Acb synaptic transmission ex vivo and in vitro. Intraperitoneal OLZ treatment reduced Acb GABAergic activity in WT but not MCHKO neurons. This effect was also seen in vitro by applying OLZ to acute brain slices. OLZ reduced the frequency and amplitude of GABAergic activity that was more robust in WT than MCHKO Acb. These findings indicate that OLZ reduced Acb GABAergic transmission and that MCH is necessary for the hypolocomotor effects of OLZ.

Neuroanatomical substrates of the disruptive effect of olanzapine on rat maternal behavior as revealed by c-Fos immunoreactivity

Olanzapine is one of the most widely prescribed atypical antipsychotic drugs in the treatment of schizophrenia. Besides its well-known side effect on weight gain, it may also impair human parental behavior. In this study, we took a preclinical approach to examine the behavioral effects of olanzapine on rat maternal behavior and investigated the associated neural basis using the c-Fos immunohistochemistry. On postpartum days 6-8, Sprague-Dawley mother rats were given a single injection of sterile water or olanzapine (1.0, 3.0 or 5.0mg/kg, sc). Maternal behavior was tested 2h later, after which rats were sacrificed and brain tissues were collected. Ten brain regions that were either implicated in the action of antipsychotic drugs and/or in the regulation of maternal behavior were examined for c-Fos immunoreactivity. Acute olanzapine treatment dose-dependently disrupted various components of maternal behavior (e.g., pup retrieval, pup licking, nest building, crouching) and increased c-Fos immunoreactivity in the medial prefrontal cortex (mPFC), nucleus accumbens shell and core (NAs and NAc), dorsolateral striatum (DLSt), ventral lateral septum (LSv), central amygdala (CeA) and ventral tegmental area (VTA), important brain areas generally implicated in the incentive motivation and reward processing. In contrast, olanzapine treatment did not alter c-Fos in the medial preoptic nucleus (MPN), ventral bed nucleus of the stria terminalis (vBST) and medial amygdala (MeA), the core brain areas directly involved in the mediation of rat maternal behavior. These findings suggest that olanzapine disrupts rat maternal behavior primarily by suppressing incentive motivation and reward processing via its action on the mesocorticolimbic dopamine systems, other limbic and striatal areas, but not by disrupting the core processes involved in the mediation of maternal behavior in particular.

Different antipsychotics elicit different effects on magnocellular oxytocinergic and vasopressinergic neurons as revealed by Fos immunohistochemistry

Acute administration of antipsychotics elicits regionally distinct patterns of Fos expression in the rat brain. Stimulation of oxytocin (OXY) and vasopressin (AVP) release in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei indicates that antipsychotics may play a role in autonomic, neuroendocrine, and behavioral processes. This study was focused to reveal the responsiveness of hypothalamic OXY- and AVP- producing magnocellular neurons, in terms of quantitative and topographical distinctions, to antipsychotics displaying different pharmacological profiles. Naive male Wistar rats were injected intraperitoneally with haloperidol (1 mg/kg), clozapine (30 mg/kg), olanzapine (30 mg/kg), risperidone (2mg/kg), and vehicle (5% chremophor) and were sacrificed 60 min later by a fixative. Fos, Fos/OXY, and Fos/AVP labelings were visualized by immunohistochemistry in the SON, 5 accessory (ACS) cell groups, and 4 distinct PVN subdivisions using a computerized light microscope. Most apparent activation of single Fos, Fos/OXY, and Fos/AVP cells was induced by clozapine and olanzapine; effects of risperidone and haloperidol were substantially lower; no colocalizations were revealed in naive or vehicle treated control rats. The data indicate the existence of a substantial diversity in the stimulatory effect of the selected antipsychotics on quantity of Fos, Fos/OXY, and Fos/AVP immunostainings with the preferential action of the atypicals clozapine over olanzapine and little effects of risperidone and haloperidol. Variabilities in Fos distribution in the PVN, SON, and ACS induced by antipsychotics may be helpful to understand more precisely the extent of their extra-forebrain actions with possible presumption of their functional impact and side effect consequences.

Chronic olanzapine activates the Stat3 signal transduction pathway and alters expression of components of the 5-HT2A receptor signaling system in rat frontal cortex

The mechanisms underlying desensitization of serotonin 2A (5-HT(2A)) receptor signaling by antagonists are unclear but may involve changes in gene expression mediated via signal transduction pathways. In cells in culture, olanzapine causes desensitization of 5-HT(2A) receptor signaling and increases the levels of regulators of G protein signaling (RGS) 7 protein dependent on phosphorylation/activation of the Janus kinase 2 (Jak2)/signal transducers and activators of transcription 3 (Stat3) signaling pathway. In the current study, the 5-HT(2A) receptor signaling system in rat frontal cortex was examined following 7 days of daily treatment with 0.5, 2.0 or 10.0 mg/kg i.p. olanzapine. Olanzapine increased phosphorylation of Stat3 in rats treated daily with 10 mg/kg olanzapine and caused a dose-dependent desensitization of 5-HT(2A) receptor-mediated phospholipase C activity. There were dose-dependent increases in the levels of membrane-associated 5-HT(2A) receptor, G(alpha11) and G(alphaq) protein levels but no changes in the G(beta) protein levels. With olanzapine treatment, RGS4 protein levels increase in the membrane-fraction and decrease in the cytosolic fraction by similar amounts suggesting a redistribution of RGS4 protein within neurons. RGS7 protein levels increase in both the membrane and cytosolic fractions in rats treated daily with 10mg/kg olanzapine. The olanzapine-induced increase in Stat3 activity could underlie the increase in RGS7 protein expression in vivo as previously demonstrated in cultured cells. Furthermore, the increases in membrane-associated RGS proteins could play a role in desensitization of signaling by terminating the activated G(alphaq/11) proteins more rapidly.

Effects of a preincisional 14-day course of valerian on natural killer cell activity in Sprague-Dawley male rats undergoing abdominal surgery

INTRODUCTION

The American Cancer Society estimated that more than 1 million new cancer cases were diagnosed in 2005 and a majority of these patients died from metastatic spread. The standard for treating solid tumor cancer is surgical resection. However, it has been suggested that surgical resection may, in fact, promote metastasis. One of the body's natural defenses to combat metastasis is the activity of natural killer (NK) cells. NK cells serve as a vital mediator of detection during the early innate immune response and destruction of aberrant cells. It has been demonstrated that benzodiazepines may ameliorate surgery-induced suppression of NK cell activity. We examined the effect of a 14-day course of valerian, a herbal anxiolytic, on NK cell activity in Sprague-Dawley rats.

METHODS

Thirty-five rats were assigned to 1 of 3 groups: (1) surgical animals administered research grade valerian, 15 mg/kg solubilized in peanut oil; (2) surgical animals administered peanut oil (vehicle); and (3) anesthesia-only animals administered valerian. One day before the 14-day course of valerian, blood was drawn to assay baseline NK cell activity. On experimental day, all animals were administered isoflurane anesthesia. Surgical animals underwent a standard laparotomy whereas anesthesia-only rats were anesthetized for the same period of time as the surgical rats. Twenty-four hours postexperiment animals underwent a second blood draw to assay NK cell activity.

RESULTS

Analysis of covariance (ANCOVA) was used to analyze NK cell activity (measured in lytic units). Our results suggested that there was no difference (P = .9) in suppression within or between groups.

CONCLUSIONS

Clinical studies with valerian have been published but with small numbers and some ambiguity. Further research regarding valerian's effectiveness as a modulator of NK cell activity and whether dosage or route of administration is a factor in modulation is still warranted.

Olanzapine and JL13 induce cross-tolerance to the clozapine discriminative stimulus in rats

We have previously shown that chronic treatment with clozapine induces tolerance to the clozapine discriminative stimulus in rats. The studies reported here extended this work to assess whether chronic treatment with the clozapine-like antipsychotics olanzapine and 5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5] benzoxazepine fumarate (JL13) induced cross-tolerance to clozapine. Two groups of rats were trained to discriminate clozapine (5 mg/kg, intraperitoneal). Training was suspended and the rats were treated with either olanzapine or JL13 at high doses (5 and 20 mg/kg, respectively). These doses were administered twice daily. The clozapine generalization curve was computed three times - before chronic drug treatment, after 10 days of chronic treatment, and after 16 drug-free days. Both olanzapine and JL13 induced cross-tolerance to the clozapine stimulus, shown by significant 3.4 and 3.9 fold parallel shifts to the right in the clozapine generalization curves. Cross-tolerance was lost spontaneously during the drug-free days after treatment as clozapine sensitivity returned to baseline. We interpret these findings as indicative of the development of pharmacodynamic cross-tolerance to clozapine. Possible neuroadaptive mechanisms involved in such cross-tolerance are discussed. The paradigm outlined here allows refinement of antipsychotic drug discrimination assays to identify common chronic effects of such drugs.

Effects of short-term and chronic olanzapine treatment on immediate early gene protein and tyrosine hydroxylase immunoreactivity in the rat locus coeruleus and medial prefrontal cortex

Atypical antipsychotic drugs, such as olanzapine, have been reported to activate the locus coeruleus (LC) and lead to acute expression of the Fos-like immediate early gene (IEG) protein in the LC and medial prefrontal cortex (mPFC). Stimuli that activate the LC have been reported to increase expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis. However, the effects of chronic treatment with olanzapine on IEG expression and the dose-dependence of the effects of olanzapine on IEG and TH expression are not known. Thus, we examined Fos-like, c-Jun, activating transcription factor 2 (ATF-2), early growth response 1 (Egr-1), early growth response 2 (Egr-2), and TH immunoreactivity expression in the LC and mPFC in rats receiving 2, 4, 8, or 15 mg/kg/day olanzapine by s.c. osmotic minipump for 4 h, 1 week, 2 weeks, or 4 weeks. ATF-2 expression was up-regulated at all treatment durations, while Egr-1 and Egr-2 were down-regulated in both the LC and mPFC. Fos-like expression was up-regulated through 2 weeks, but not 4 weeks, in both the LC and mPFC. C-Jun expression was up-regulated for 4 weeks in the LC and for 2 weeks, but not 4 weeks, in the mPFC. At all doses, there were rapid and sustained increases in TH immunoreactivity in the LC, but only delayed increases in the mPFC. These data indicate that olanzapine has rapid effects on IEG in the LC and mPFC, many of which are sustained through four weeks of treatment. Further, these data indicate that the delayed increase in TH expression in the mPFC parallels, and may play an important role in, the increased efficacy of olanzapine that emerges over time in humans.

Chronic high-dose haloperidol has qualitatively similar effects to risperidone and clozapine on immediate-early gene and tyrosine hydroxylase expression in the rat locus coeruleus but not medial prefrontal cortex

Acute administration of clozapine has been reported to activate the locus coeruleus (LC) and beta-adrenoceptor-dependent Fos immunoreactivity in the medial prefrontal cortex (mPFC) in rodents. Haloperidol is reported to exhibit a similar acute effect on LC firing and beta-adrenoceptor dependent Fos immunoreactivity in the mPFC but only at high doses. We compared the effects of chronic 4-week treatment with risperidone (1mg/kg/day s.c.), clozapine (10mg/kg/day s.c.) or a high dose of haloperidol (4mg/kg/day s.c.) on immediate-early gene protein (c-Fos, Egr-1 and Egr-2) and tyrosine hydroxylase (TH) expression. In the mPFC, haloperidol decreased, whereas clozapine increased, c-Fos immunoreactivity. Only haloperidol increased Egr-1 immunoreactivity. There was no significant effect on Egr-2 immunoreactivity. In the LC, both Egr-1 and Egr-2 expression was down regulated by all three antipsychotics. Clozapine and risperidone increased TH immunoreactivity in both mPFC and LC. Haloperidol caused a smaller increase in TH expression in the LC, but did not alter expression in the mPFC. In conclusion, despite qualitatively similar effects in the LC, chronic treatment with haloperidol had different effects to clozapine and risperidone in the mPFC. This may relate to the reported advantage of clozapine and risperidone over haloperidol against prefrontal cortical-dependent cognitive and negative symptoms.

Effects of chronic neuroleptic treatments on nutrient selection, body weight, and body composition in the male rat under dietary self-selection

New antipsychotic drugs often increase weight and produce metabolic disturbances in treated patients. However, the mechanisms by which neuroleptics induce these undesirable side effects in humans are not known. Studies have shown that antipsychotics can increase body weight in female but not in male rats. However, no studies investigated changes in macronutrient selection during chronic treatments with antipsychotics in male rats, and no studies investigated precisely body composition after such treatments. In the present work, we studied in male rats the effects of long-term administration of two neuroleptics: haloperidol, a classical neuroleptic which has a moderate effect on weight gain in humans, and olanzapine, an atypical neuroleptic which has a more important effect on weight gain. Treatments (both 1 mg/kg) were given orally for 6 weeks, and the animals were allowed to self-select food among carbohydrates, lipids and proteins. Food selection was measured throughout the study, and body composition was measured by dissection and weighing of the main organs and tissues. Circulating leptin, insulin and glucose were also assayed at the end of the study on blood collected at the time of carcass analysis. The results show that none of the neuroleptic treatments modified caloric intake, food selection, body weight, and body composition. Olanzapine produced a statistically non-significant increase in subcutaneous fat tissue. It is concluded that a 6-week olanzapine or haloperidol treatment in male rats under dietary macronutrient selection does not significantly affect energy regulation.

Fast Fos: rapid protocols for single- and double-labeling c-Fos immunohistochemistry in fresh frozen brain sections

Immunohistochemical localization of c-Fos immunoreactivity has been used successfully for over a decade to visualize patterns of neuronal activity in the brain and spinal cord. These experiments are extremely useful in identifying physiological or pharmacological activation of specific populations of neurons. Unfortunately, conventional c-Fos immunohistochemical protocols are very time and resource intensive. We have adapted and optimized established c-Fos immunohistochemistry (IHC) methodologies for use with fresh frozen brain tissue mounted directly onto slides. The resultant rapid protocols, which we refer to as "Fast Fos", include applications for single- and double-labeling, utilizing either enzyme-substrate or fluorescent detection systems. These protocols provide increased assay throughput and reproducibility, which can be further enhanced by use of an automated slide stainer. Taken as a whole, the c-Fos IHC protocols described in this report provide a flexible system for the identification of neuronal activation that substantially reduces time and resource expenditure while increasing quality and reproducibility of data.

Regulation of affect by the lateral septum: implications for neuropsychiatry

Substantial evidence indicates that the lateral septum (LS) plays a critical role in regulating processes related to mood and motivation. This review presents findings from the basic neuroscience literature and from some clinically oriented research, drawing from behavioral, neuroanatomical, electrophysiological, and molecular studies in support of such a role, and articulates models and hypotheses intended to advance our understanding of these functions. Neuroanatomically, the LS is connected with numerous regions known to regulate affect, such as the hippocampus, amygdala, and hypothalamus. Through its connections with the mesocorticolimbic dopamine system, the LS regulates motivation, both by stimulating the activity of midbrain dopamine neurons and regulating the consequences of this activity on the ventral striatum. Evidence that LS function could impact processes related to schizophrenia and other psychotic spectrum disorders, such as alterations in LS function following administration of antipsychotics and psychotomimetics in animals, will also be presented. The LS can also diminish or enable fear responding when its neural activity is stimulated or inhibited, respectively, perhaps through its projections to the hypothalamus. It also regulates behavioral manifestations of depression, with antidepressants stimulating the activity of LS neurons, and depression-like phenotypes corresponding to blunted activity of LS neurons; serotonin likely plays a key role in modulating these functions by influencing the responsiveness of the LS to hippocampal input. In conclusion, a better understanding of the LS may provide important and useful information in the pursuit of better treatments for a wide range of psychiatric conditions typified by disregulation of affective functions.

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.

Induction of differential patterns of local cerebral glucose metabolism and immediate-early genes by acute clozapine and haloperidol

Atypical antipsychotic drugs, such as clozapine, show many differences in their actions as compared to typical antipsychotic drugs, such as haloperidol. In particular, the neuroanatomical substrates responsible for the superior therapeutic profile of clozapine are unknown. In order to identify regions of the CNS which are affected either differentially or in parallel by clozapine and haloperidol, we have used 2-deoxyglucose autoradiography to monitor local cerebral glucose utilisation (LCGU), in parallel with in situ hybridisation to monitor the expression of five immediate-early genes (c-fos, fos B, fra 1, fra 2 and zif 268). Clozapine (20 mg/kg i.p.) caused a reduction in LCGU in many areas of the psychosis-related corticolimbothalamic and Papez circuits, such as the anterior cingulate and retrosplenial cortices and the mammillary body. Haloperidol (1 mg/kg i.p.) showed less ability to modulate LCGU in these regions. Clozapine also increased immediate-early gene expression in these limbic circuits, although the pattern of induction was different for each gene, and also differed from the pattern of effects on LCGU. The only region which displayed similar effects with both antipsychotics was the anteroventral thalamus, with LCGU and c-fos mRNA expression being altered similarly by both drugs. This further supports the hypothesis of the thalamus being a common site of antipsychotic action. Since the Papez circuit has been implicated in emotive learning, and to be involved in mediating the negative symptoms associated with schizophrenia, the greater action of clozapine on regions within this circuit may also provide clues to the atypical antipsychotic's superior efficacy against negative symptoms. This is one of the first studies which provides a direct comparison of regional activity as assessed by LCGU and by a panel of IEGs. The results emphasise the necessity of monitoring a number of different parameters of regional activity in order to identity the neuroanatomical substrate for actions of a drug in the CNS.

Olanzapine: a review of its use in the treatment of bipolar I disorder

Olanzapine, a thienobenzodiazepine derivative, is a psychotropic agent that has shown efficacy in the treatment of patients with bipolar I disorder. Olanzapine has a multireceptorial binding profile including a greater affinity for serotonin 5-HT(2A) than for dopamine D(2) receptors. Olanzapine 5 to 20 mg/day demonstrated significantly greater antimanic efficacy than placebo in two double-blind, randomised 3- or 4-week trials of patients with bipolar I disorder of either manic or mixed episodes, with or without psychotic features. Additionally, in one of these trials, improvements in cognitive function and hostility were superior with olanzapine. In cohorts of severely depressed and rapid cycling patients, improvements in manic and depressive symptoms and in manic symptoms only, were superior with olanzapine compared with placebo. Significant improvements from baseline in symptoms of mania, depression, cognitive functioning and hostility were seen with olanzapine in a 49-week extension phase study. In double-blind trials, olanzapine 10 mg/day appeared to have similar antimanic efficacy to oral lithium 400mg twice daily in the treatment of patients with pure mania (4-week small study). In patients with acute manic or mixed episodes olanzapine 5 to 20 mg/day appeared to be more effective than oral valproate semisodium (divalproex sodium) 500 to 2500 mg/day (3-week study) and at least as effective as oral haloperidol 3 to 15 mg/day (12-week study). Preliminary results from a large 6-week placebo-controlled study suggest that olanzapine 5 to 20 mg/day in combination with mood stabilisers (lithium or valproate semisodium) provides effective augmentation of antimanic treatment of patients with bipolar I disorder, with benefits seen in the first week. Adverse events reported significantly more often with olanzapine than with placebo were somnolence, dry mouth, dizziness and bodyweight gain, and in comparison with valproate semisodium were somnolence, dry mouth, increased appetite and bodyweight gain. Olanzapine was generally well tolerated with no clinically relevant abnormalities in laboratory tests, vital signs or electrocardiogram results.

CONCLUSION

Olanzapine demonstrated superior efficacy compared with placebo in the short-term treatment of patients with bipolar I disorder with manic or mixed episodes, with or without psychotic features, and was generally well tolerated. According to preliminary data the antimanic efficacy of olanzapine appears similar to that of haloperidol and better than that of valproate semisodium in patients with bipolar I disorder experiencing a manic or mixed episode; among nonpsychotic patients with manic or mixed episodes olanzapine appears to be superior to haloperidol. Available data support the choice of olanzapine as an option in the short-term management of mania in patients with bipolar I disorder with manic or mixed episodes, with or without psychotic features.

Olanzapine activates the rat locus coeruleus: in vivo electrophysiology and c-Fos immunoreactivity

BACKGROUND

Activation of central noradrenergic pathways by atypical antipsychotics has been hypothesized to play a role in their efficacy in treating the negative symptoms and cognitive impairment of schizophrenia. Because acute administration of the atypical antipsychotic olanzapine has been shown to increase extracellular levels of norepinephrine in the medial prefrontal cortex, we examined the effects of olanzapine on the noradrenergic cells of the locus coeruleus (LC).

METHODS

The effects of olanzapine (0.25-16 mg kg(-1), IV) on the firing rates and patterns of LC neurons were determined by extracellular, single-unit recordings in chloral hydrate-anaesthetized rats. The effects of olanzapine and clozapine on c-Fos expression in the LC, nucleus subcoeruleus part alpha (SubCA), and nucleus A5 (A5) were studied by immunohistochemistry.

RESULTS

Olanzapine increased LC cell firing rates, de-regularized firing, and induced burst firing. Induction of c-Fos expression in the LC by olanzapine and clozapine was confirmed and was also found in the SubCA, but not in A5.

CONCLUSIONS

Acute administration of olanzapine activates the noradrenergic neurons of the rat LC. This increased activity of LC neurons may play an important role in the efficacy of olanzapine and clozapine in treating both the negative symptoms and cognitive impairment observed in schizophrenic patients.

Interactions between environmental stimulation and antipsychotic drug effects on forebrain c-fos activation

The immediate-early gene product Fos is differentially induced in the rat brain by the antipsychotic drugs haloperidol and clozapine. It is often claimed that although both drugs induce Fos in the nucleus accumbens, haloperidol but not clozapine increases Fos-like immunoreactivity in the striatum, whereas clozapine but not haloperidol increases Fos-like immunoreactivity in prefrontal cortex. Investigations of antipsychotic drug effects on Fos have typically administered high doses with pronounced sedative effects to behaviorally naive animals. In the present study, we compared the effects of low doses of haloperidol (0.1 mg/kg) and clozapine (5 mg/kg) on Fos-like immunoreactivity in rats which were either behaviorally naive, exposed to a novel environment or tested for two-way active avoidance. We determined that haloperidol increased Fos in the striatum and nucleus accumbens regardless of testing condition whereas clozapine markedly reduced the induction of Fos by behavioral testing in these regions; moreover, haloperidol dramatically increased prefrontal cortical Fos expression in animals placed in a novel environment, but not in testing-naive controls. From these results we suggest that antipsychotic drug-induced patterns of Fos expression in the rat are highly dependent on animals' concurrent behavioral status, perhaps reflecting neuroanatomically specific interactions between antipsychotic drugs and environmental stressors which also may occur in the schizophrenic condition.

The muscarinic agonist xanomeline increases monoamine release and immediate early gene expression in the rat prefrontal cortex

BACKGROUND

The muscarinic agonist xanomeline has been shown to reduce antipsychotic-like behaviors in patients with Alzheimer's disease. Because atypical antipsychotic agents increase dopamine release in prefrontal cortex and induce immediate early gene expression in prefrontal cortex and nucleus accumbens, the effect of xanomeline was determined on these indices.

METHODS

The effect of xanomeline on extracellular levels of monoamines in brain regions was determined using a microdialysis technique, and changes in expression of the immediate early genes c-fos and zif/268 in brain regions were evaluated using in situ hybridization histochemistry.

RESULTS

Xanomeline increased extracellular levels of dopamine in prefrontal cortex and nucleus accumbens but not in striatum. Xanomeline increased expression of c-fos and zif/268 in prefrontal cortex and nucleus accumbens. There was no change in immediate early gene expression in striatum.

CONCLUSIONS

Xanomeline increased extracellular levels of dopamine, which is similar to the effects of the atypical antipsychotics clozapine and olanzapine. The regional pattern of immediate early gene expression induced by xanomeline resembled that of atypical antipsychotic agents. Based on the antipsychotic-like activity of xanomeline in Alzheimer's patients and the similarity to atypical antipsychotic agents, we suggest that xanomeline may be a novel antipsychotic agent.

Clozapine-induced Fos-protein expression in rat forebrain regions: differential effects of adrenalectomy and corticosterone supplement

Unlike classical antipsychotic drugs, clozapine activates the hypothalamo-pituitary-adrenal axis and induces a specific regional pattern of Fos-protein expression in the rat forebrain. Whether corticosterone plays a role in the clozapine-induced Fos response is the subject of this study. Some rats were adrenalectomized and in a number, including intact animals, a corticosterone pellet (100 mg s.c.) was implanted; after 1 week, a single dose of clozapine (20 mg kg(-1) i.p.) was administered. The clozapine-induced Fos response was not affected by adrenalectomy, apart from the nucleus accumbens shell, the subfornical organ and the supraoptic nucleus; there was an increased response in the nucleus accumbens shell, while other regions showed less Fos immunoreactivity. Implantation of the corticosterone pellet in both sham-operated and adrenalectomized animals, reduced the clozapine-induced Fos responses strongly in the hypothalamic paraventricular nucleus, the subfornical organ and possibly in the prefrontal cortex; in the supraoptic nucleus, this effect was seen only in intact animals. The effect of clozapine on plasma corticosterone levels was also diminished by supplemental corticosterone treatment. These results imply that the effects of clozapine are partially dependent upon hypothalamo-pituitary-adrenal axis integrity and activation. The efficacy of clozapine in the treatment of polydipsia and hyponatremia in chronic psychiatric patients may involve clozapine-mediated activation of the cellular activity in the subfornical organ.

Limited participation of 5-HT(1A) and 5-HT(2A/2C) receptors in the clozapine-induced Fos-protein expression in rat forebrain regions

Through the development of tolerance following long-term clozapine treatment, we investigated whether 5-HT(1A) and 5-HT(2A/2C) receptors participate in the clozapine-induced Fos-protein expression in the rat forebrain. Tolerance exists when the acutely increased Fos responses to a challenge dose of the 5-HT(1A) and 5-HT(2A/2C) agonists 1-(2, 5-dimethoxy-4-iodophenyl)-2-aminopropane-hydrochloride (DOI) and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), respectively, given simultaneously to rats, are attenuated after 3-week clozapine (20 mg kg(-1) day(-1) i.p.) pretreatment. As compared to the acute effects of clozapine, the Fos responses to concomitant administration of the 5-HT receptor agonists DOI (2.5 mg kg(-1) i.p. ) and 8-OH-DPAT (2.5 mg kg(-1) i.p.) were more pronounced in the prefrontal cortex, the nucleus accumbens core and the dorsomedial and ventromedial striatum, areas in which clozapine (20 mg kg(-1) i. p.) exhibited marginal effects. In the hypothalamic paraventricular nucleus, both clozapine and DOI/8-OH-DPAT induced a remarkably high number of Fos-positive nuclei. Long-term clozapine pretreatment attenuated the acutely induced Fos expression of the 5-HT receptor agonists in the nucleus accumbens core, the dorsomedial and ventromedial parts of the striatum and the lateral septum, indicating (partial) common sites of action of the agents in these brain regions. No tolerance was found in the nucleus accumbens shell and the hypothalamic paraventricular nucleus and the central amygdala, suggesting that the clozapine-induced Fos responses, though distinct in these regions, are independent of 5-HT receptors. The prefrontal cortex and the dorsolateral striatum indicated only a tendency towards tolerance. In addition, the involvement of the tested 5-HT receptor agonists in the clozapine-enhanced release of plasma corticosterone became apparent. The present results indicate that the clozapine-induced patterns of Fos expression in the rat forebrain can only be in part attributed to an interaction with 5-HT(1A/2A/2C) receptors.