Enhancement of laminar FosB expression in frontal cortex of rats receiving long chronic clozapine administration

Leptin in the hindbrain facilitates phosphorylation of STAT3 in the hypothalamus

Leptin receptors (ObRs) in the forebrain and hindbrain have been independently recognized as important mediators of leptin responses. We recently used low-dose leptin infusions to show that chronic activation of both hypothalamic and hindbrain ObRs is required to reduce body fat. The objective of the present study was to identify the brain nuclei that are selectively activated in rats that received chronic infusion of leptin in both the forebrain and hindbrain. Either saline or leptin was infused into third and fourth ventricles (0.1 μg/24 h in the third ventricle and 0.6 μg/24 h in the fourth ventricle) of male Sprague-Dawley rats for 6 days using Alzet pumps. Rats infused with leptin into both ventricles (LL rats) showed a significant increase in phosphorylated (p)STAT3 immunoreactivity in the arcuate nucleus, ventromedial hypothalamus, dorsomedial hypothalamus, and posterior hypothalamus compared with other groups. No differences in pSTAT3 immunoreactivity were observed in midbrain or hindbrain nuclei despite a sixfold higher infusion of leptin into the fourth ventricle than the third ventricle. ΔFosB immunoreactivity, a marker of chronic neuronal activation, showed that multiple brain nuclei were chronically activated due to the process of infusion, but only the arcuate nucleus, ventromedial hypothalamus, dorsomedial hypothalamus, and ventral tuberomamillary nucleus showed a significant increase in LL rats compared with other groups. These data demonstrate that low-dose leptin in the hindbrain increases pSTAT3 in areas of the hypothalamus known to respond to leptin, supporting the hypothesis that leptin-induced weight loss requires an integrated response from both the hindbrain and forebrain.

Cannabidiol attenuates sensorimotor gating disruption and molecular changes induced by chronic antagonism of NMDA receptors in mice

BACKGROUND

Preclinical and clinical data suggest that cannabidiol (CBD), a major non-psychotomimetic compound from Cannabis sativa, induces antipsychotic-like effects. However, the antipsychotic properties of repeated CBD treatment have been poorly investigated. Behavioral changes induced by repeated treatment with glutamate N-methyl-D-aspartate receptor (NMDAR) antagonists have been proposed as an animal model of schizophrenia-like signs. In the present study, we evaluated if repeated treatment with CBD would attenuate the behavioral and molecular modifications induced by chronic administration of one of these antagonists, MK-801.

METHODS

Male C57BL/6J mice received daily i.p. injections of MK-801 (0.1, 0.5, or 1mg/kg) for 14, 21, or 28 days. Twenty-four hours after the last injection, animals were submitted to the prepulse inhibition (PPI) test. After that, we investigated if repeated treatment with CBD (15, 30, and 60mg/kg) would attenuate the PPI impairment induced by chronic treatment with MK-801 (1mg/kg; 28 days). CBD treatment began on the 6th day after the start of MK-801 administration and continued until the end of the treatment. Immediately after the PPI, the mice brains were removed and processed to evaluate the molecular changes. We measured changes in FosB/ΔFosB and parvalbumin (PV) expression, a marker of neuronal activity and a calcium-binding protein expressed in a subclass of GABAergic interneurons, respectively. Changes in mRNA expression of the NMDAR GluN1 subunit gene (GRN1) were also evaluated. CBD effects were compared to those induced by the atypical antipsychotic clozapine.

RESULTS

MK-801 administration at the dose of 1mg/kg for 28 days impaired PPI responses. Chronic treatment with CBD (30 and 60mg/kg) attenuated PPI impairment. MK-801 treatment increased FosB/ΔFosB expression and decreased PV expression in the medial prefrontal cortex. A decreased mRNA level of GRN1 in the hippocampus was also observed. All the molecular changes were attenuated by CBD. CBD by itself did not induce any effect. Moreover, CBD effects were similar to those induced by repeated clozapine treatment.

CONCLUSIONS

These results indicate that repeated treatment with CBD, similar to clozapine, reverses the psychotomimetic-like effects and attenuates molecular changes observed after chronic administration of an NMDAR antagonist. These data support the view that CBD may have antipsychotic properties.

Effects of typical and atypical antipsychotic drugs on gene expression profiles in the liver of schizophrenia subjects

BACKGROUND

Although much progress has been made on antipsychotic drug development, precise mechanisms behind the action of typical and atypical antipsychotics are poorly understood.

METHODS

We performed genome-wide expression profiling to study effects of typical antipsychotics and atypical antipsychotics in the postmortem liver of schizophrenia patients using microarrays (Affymetrix U133 plus2.0). We classified the subjects into typical antipsychotics (n = 24) or atypical antipsychotics (n = 26) based on their medication history, and compared gene expression profiles with unaffected controls (n = 34). We further analyzed individual antipsychotic effects on gene expression by sub-classifying the subjects into four major antipsychotic groups including haloperidol, phenothiazines, olanzapine and risperidone.

RESULTS

Typical antipsychotics affected genes associated with nuclear protein, stress responses and phosphorylation, whereas atypical antipsychotics affected genes associated with golgi/endoplasmic reticulum and cytoplasm transport. Comparison between typical antipsychotics and atypical antipsychotics further identified genes associated with lipid metabolism and mitochondrial function. Analyses on individual antipsychotics revealed a set of genes (151 transcripts, FDR adjusted p < 0.05) that are differentially regulated by four antipsychotics, particularly by phenothiazines, in the liver of schizophrenia patients.

CONCLUSION

Typical antipsychotics and atypical antipsychotics affect different genes and biological function in the liver. Typical antipsychotic phenothiazines exert robust effects on gene expression in the liver that may lead to liver toxicity. The genes found in the current study may benefit antipsychotic drug development with better therapeutic and side effect profiles.

Lipopolysaccharide induces delayed FosB/DeltaFosB immunostaining within the mouse extended amygdala, hippocampus and hypothalamus, that parallel the expression of depressive-like behavior

Proinflammatory cytokines induce both sickness behavior and depression, but their respective neurobiological correlates are still poorly understood. The aim of the present study was therefore to identify in mice the neural substrates of sickness and depressive-like behavior induced by lipopolysaccharide (LPS, 830 microg/kg, intraperitoneal). LPS-induced depressive-like behavior was dissociated from LPS-induced sickness by testing mice either at 6 h (at which time sickness was expected to be maximal) or at 24 h post-LPS (at which time sickness was expected to be minimal and not to bias the measurement of depressive-like behavior). Concurrently, the expression of acute and chronic cellular reactivity markers (c-Fos and FosB/DeltaFosB, respectively) was mapped by immunohistochemistry at these two time points. In comparison to saline, LPS decreased motor activity in a new cage at 6 h but not at 24 h. In contrast, the duration of immobility in the tail suspension test was increased at both 6 and 24 h. This dissociation between decreased motor activity and depressive-like behavior was confirmed at 24 h post-LPS in the forced swim test. LPS also decreased sucrose consumption at 24 and 48 h, despite normal food and water consumption by that time. At 24 h post-LPS, LPS-induced depressive-like behavior was associated with a delayed cellular activity (as assessed by FosB/DeltaFosB immunostaining) in specific brain structures, particularly within the extended amygdala, hippocampus and hypothalamus, whereas c-Fos labeling was markedly decreased by that time in all the brain areas at 6 h post-LPS. These results provide the first evidence in favor of a functional dissociation between the brain structures that underlie cytokine-induced sickness behavior and cytokine-induced depressive-like behavior, and provide important cues about the neuroanatomical brain circuits through which cytokines could have an impact on affect.

Neonatal ventral hippocampal lesions produce an elevation of DeltaFosB-like protein(s) in the rodent neocortex

Rats that have sustained bilateral excitotoxic lesions of the ventral hippocampus (VH) as neonates develop behavioral abnormalities as adults (hyper-responsiveness to stress, diminished prepulse inhibition, and increased sensitivity to dopamine agonists), which resemble certain aspects of schizophrenia. Although this behavioral profile is thought to reflect dysregulation of the mesolimbic dopamine system, the precise neuroanatomical and neurochemical substrates that mediate the emergence of these abnormalities during brain maturation are unclear. In order to identify putative sites responsible for the development of behavioral abnormalities following neonatal lesions of the VH, we utilized the chronic neuronal activity marker DeltaFosB. By comparison to sham lesioned animals, bilateral destruction of the VH elevated DeltaFosB expression throughout the caudate putamen and neocortex of animals lesioned as neonates. These increases were not observed in rats lesioned as young-adults, suggesting that DeltaFosB induction in the cortex of neonatally lesioned rats may be related to altered cortical neurodevelopment. Accumulating evidence implicates DeltaFosB in mediation of the long-lasting effects of altered dopaminergic neurotransmission on behavior. The present findings are consistent with this proposal and suggest that elevated expression of DeltaFosB identifies overactive neurons that may contribute to the enhanced sensitivity to stress and dopaminergic agonists of rats that have sustained bilateral ventral hippocampal lesions as neonates.

DeltaFosB accumulates in a GABAergic cell population in the posterior tail of the ventral tegmental area after psychostimulant treatment

The transcription factor deltaFosB is induced in the nucleus accumbens and dorsal striatum by chronic exposure to several drugs of abuse, and increasing evidence supports the possibility that this induction is involved in the addiction process. However, to date there has been no report of deltaFosB induction by drugs of abuse in the ventral tegmental area (VTA), which is also a critical brain reward region. In the present study, we used immunohistochemistry to demonstrate that chronic forced administration of cocaine induces deltaFosB in the rat VTA. This induction occurs selectively in a gamma-aminobutyric acid (GABA) cell population within the posterior tail of the VTA. A similar effect is seen after chronic cocaine self-administration. Induction of deltaFosB in the VTA occurs after psychostimulant treatment only: it is seen with both chronic cocaine and amphetamine, but not with chronic opiates or stress. The expression of deltaFosB appears to be mediated by dopamine systems, as repeated administration of a dopamine uptake inhibitor induced deltaFosB in the VTA, while administration of serotonin or norepinephrine uptake inhibitors failed to produce this effect. Time course analysis showed that, following 14 days of cocaine administration, deltaFosB persists in the VTA for almost 2 weeks after cocaine withdrawal. This accumulation and persistence may account for some of the long-lasting changes in the brain associated with chronic drug use. These results provide the first evidence of deltaFosB induction in a discrete population of GABA cells in the VTA, which may regulate the functioning of the brain's reward mechanisms.

D1 dopamine receptors modulate deltaFosB induction in rat striatum after intermittent morphine administration

Induction of the transcription factor deltaFosB was studied to examine neurochemical adaptations produced by repeated opiate administration. The mechanism of this induction was also investigated. The 35- to 37-kDa isoforms of deltaFosB, also referred to as the chronic Fras, were measured in the nucleus accumbens, caudate putamen, and frontal cortex of male Sprague-Dawley rats after either an acute injection of morphine or an escalating dosing schedule of morphine for 10 days. Heroin was also tested to determine whether the findings extend to other opiates. Results from Western blot analysis using an anti-fosB antibody demonstrate that 10-day intermittent escalating dose morphine produced a significant increase in deltaFosB-immunoreactivity in the nucleus accumbens, caudate putamen and frontal cortex, whereas a single injection of morphine had no effect on Fra immunoreactivity. Heroin administered twice daily for 10 days by an intermittent escalating dose schedule also induced deltaFosB in the caudate putamen, but not in the nucleus accumbens or frontal cortex. Daily pretreatment with the selective D1-like dopamine receptor antagonist SCH 23390 [R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride] significantly blocked morphine-induced deltaFosB induction in the nucleus accumbens and caudate putamen, but not in the frontal cortex. These results demonstrate that morphine-induced deltaFosB up-regulation in the striatum, but not in the frontal cortex, is modulated by D1 dopamine receptors, suggesting that the mechanisms involved in the up-regulation of these chronic Fras by morphine is brain region-specific.

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.