Induced C-fos mRNA Expression Research Articles

Driving Neurogenesis in Neural Stem Cells with High Sensitivity Optogenetics.

Optogenetic stimulation of neural stem cells (NSCs) enables their activity-dependent photo-modulation. This provides a spatio-temporal tool for studying activity-dependent neurogenesis and for regulating the differentiation of the transplanted NSCs. Currently, this is mainly driven by viral transfection of channelrhodopsin-2 (ChR2) gene, which requires high irradiance and complex in vivo/vitro stimulation systems. Additionally, despite the extensive application of optogenetics in neuroscience, the transcriptome-level changes induced by optogenetic stimulation of NSCs have not been elucidated yet. Here, we made transformed NSCs (SFO-NSCs) stably expressing one of the step-function opsin (SFO)-variants of chimeric channelrhodopsins, ChRFR(C167A), which is more sensitive to blue light than native ChR2, via a non-viral transfection system using piggyBac transposon. We set up a simple low-irradiance optical stimulation (OS)-incubation system that induced c-fos mRNA expression, which is activity-dependent, in differentiating SFO-NSCs. More neuron-like SFO-NCSs, which had more elongated axons, were differentiated with daily OS than control cells without OS. This was accompanied by positive/negative changes in the transcriptome involved in axonal remodeling, synaptic plasticity, and microenvironment modulation with the up-regulation of several genes involved in the Ca2+-related functions. Our approach could be applied for stem cell transplantation studies in tissue with two strengths: lower carcinogenicity and less irradiance needed for tissue penetration.

Melanocortin-4 receptor in the medial amygdala regulates emotional stress-induced anxiety-like behaviour, anorexia and corticosterone secretion

The central melanocortin system has been implicated in emotional stress-induced anxiety, anorexia and activation of the hypothalamo-pituitary-adrenal (HPA) axis. However, the underlying neural substrates have not been identified. The medial amygdala (MeA) is highly sensitive to emotional stress and expresses high levels of the melanocortin-4 receptor (MC4R). This study investigated the effects of activation and blockade of MC4R in the MeA on anxiety-like behaviour, food intake and corticosterone secretion. We demonstrate that MC4R-expressing neurons in the MeA were activated by acute restraint stress, as indicated by induction of c-fos mRNA expression. Infusion of a selective MC4R agonist into the MeA elicited anxiogenic-like effects in the elevated plus-maze test and decreased food intake. In contrast, local MeA infusion of SHU 9119, a MC4R antagonist, blocked restraint stress-induced anxiogenic and anorectic effects. Moreover, plasma corticosterone levels were increased by intra-MeA infusion of the MC4R agonist under non-stressed conditions and restraint stress-induced elevation of plasma corticosterone levels was attenuated by pretreatment with SHU 9119 in the MeA. Thus, stimulating MC4R in the MeA induces stress-like anxiogenic and anorectic effects as well as activation of the HPA axis, whereas antagonizing MC4R in this region blocks such effects induced by restraint stress. Together, our results implicate MC4R signalling in the MeA in behavioural and endocrine responses to stress.

A food predictive cue must be attributed with incentive salience for it to induce c-fos mRNA expression in cortico-striatal-thalamic brain regions.

Cues associated with rewards acquire the ability to engage the same brain systems as rewards themselves. However, reward cues have multiple properties. For example, they not only act as predictors of reward capable of evoking conditional responses (CRs), but they may also acquire incentive motivational properties. As incentive stimuli they can evoke complex emotional and motivational states. Here we sought to determine whether the predictive value of a reward cue is sufficient to engage brain reward systems, or whether the cue must also be attributed with incentive salience. We took advantage of the fact that there are large individual differences in the extent to which reward cues are attributed with incentive salience. When a cue (conditional stimulus, CS) is paired with delivery of food (unconditional stimulus, US), the cue acquires the ability to evoke a CR in all rats; that is, it is equally predictive and supports learning the CS-US association in all. However, only in a subset of rats is the cue attributed with incentive salience, becoming an attractive and desirable incentive stimulus. We used in situ hybridization histochemistry to quantify the ability of a food cue to induce c-fos mRNA expression in rats that varied in the extent to which they attributed incentive salience to the cue. We found that a food cue induced c-fos mRNA in the orbitofrontal cortex, striatum (caudate and nucleus accumbens), thalamus (paraventricular, intermediodorsal and central medial nuclei), and lateral habenula, only in rats that attributed incentive salience to the cue. Furthermore, patterns of "connectivity" between these brain regions differed markedly between rats that did or did not attribute incentive salience to the food cue. These data suggest that the predictive value of a reward cue is not sufficient to engage brain reward systems-the cue must also be attributed with incentive salience.

A food predictive cue must be attributed with incentive salience for it to induce c-fos mRNA expression in cortico-striatal-thalamic brain regions

A food predictive cue must be attributed with incentive salience for it to induce c-fos mRNA expression in cortico-striatal-thalamic brain regions

Oxytocin and vasopressin in the medial amygdala differentially modulate approach and avoidance behavior toward illness-related social odor

Animals are known to recognize a specific odorant informing conspecific health condition, which plays a significant role in regulating their social communication. Here, we assess neural mechanisms regulating innate approach/avoidance response toward such conspecific odor cues in rats. Odor scent from healthy conspecifics induced approach behavior, while those from sick conspecifics produced avoidance response in odor-recipient male rats. Analysis of mRNA expression in several brain sites of odor recipient rats illustrated that induction of c-fos mRNA expression was found in the olfactory bulb (OB), the medial amygdala (MeA), the bed nucleus of stria terminalis (BnST), and the paraventricular nucleus of the hypothalamus (PVN), when exposed to conspecific odor. Moreover, in the MeA, expression of oxytocin (OT) receptor mRNA was increased when rats were exposed to healthy conspecific odor, while induction of arginine vasopressin (AVP) receptor 1a and 1b mRNA were found only when exposed to sick conspecific odor. Bilateral infusion of OT receptor (OTR) antagonist, (d(CH2)5 1,Tyr(Me) 2,Thr 4,Orn 8,des-Gly-NH2 9)-Vasotocin, into the MeA blocked approach behavior to healthy odor, while those of AVP receptor antagonists, V1a selective: (Phenylac 1,D-Tyr(Me) 2,Arg 6.8,Lys-NH2 9)-Vasopressin, and type 1 receptor antagonist: (Deamino-Pen 1, Try(Me) 2, Arg 8)-Vasopressin, into the MeA inhibited avoidance response to sick odor. These findings provide evidence for an essential role of OT and AVP receptors, especially type 1a, in the MeA in regulating approach/avoidance behaviors, respectively, in social odorant communication.

Central injections of noradrenaline induce reinstatement of cocaine seeking and increase c-fos mRNA expression in the extended amygdala

We recently reported that central injections of noradrenaline (NA) induce reinstatement of cocaine seeking in rats. Here, we replicate and extend our finding to an additional dose of NA and show that it is associated with the induction of c-fos mRNA expression (a marker of neuronal activation) in functionally relevant brain regions, including the bed nucleus of the stria terminalis and central nucleus of the amygdala.

Repeated administration of methamphetamine blocked cholecystokinin-octapeptide injection-induced c-fos mRNA expression without change in capsaicin-induced junD mRNA expression in rat cerebellum

In the cerebellum, there are numerous cholecystokinin (CCK-8)-containing fibers. Since systemic CCK-8 injection-induced anxiety (psychological stress) activates the locus coeruleus cells that send mossy fiber inputs to the cerebellum, we examined whether systemic CCK-8 injections activate the rat and mouse cerebellum. First, injections of CCK-8 were found to induce c-fos mRNA expression in a vague patchy pattern that is different from single methamphetamine-induced Zebrin band-like c-fos mRNA expression, suggesting that the CCK-8 activating mossy fibers induce gene expression differently from the dopamine-containing mossy fibers in the ventral tegmental area. Second, since CCK-8 facilitates neural activity of dopamine in the midbrain, we examined whether repeated methamphetamine administration that induced behavioral sensitization had similar effects on the cerebellar CCK system. Repeated administration of methamphetamine suppressed the CCK-8-induced c-fos mRNA expression in the rat cerebellum. Third, capsaicin injections (physical stress) into a hind limb of the rat increased junD mRNA expression with no effect on c-fos mRNA expression, and repeated methamphetamine injections had no effect on the capsaicin-induced expression of junD mRNA. Fourth, either single injection of methamphetamine or CCK-8 to mice increased c-fos mRNA expression in the locus coeruleus, and so noradrenalin, but not dopamine, might interact with CCK-8-activating system. However, we considered the possibility unlikely. Thus, we conclude that repeated methamphetamine administration though dopamine selectively inhibits the c-fos mRNA expression after CCK-8 injection in the cerebellum.

3BP2 Adapter Protein Is Required for Receptor Activator of NFκB Ligand (RANKL)-induced Osteoclast Differentiation of RAW264.7 Cells

The adapter protein 3BP2 (also known as SH3BP2 and Abl SH3-binding protein 2) has been involved in leukocyte signaling and activation downstream immunoreceptors. Genetic studies have further associated 3BP2 mutations to the human disease cherubism and to inflammation and bone dysfunction in mouse. However, how wild type 3BP2 functions in macrophage differentiation remains poorly understood. In this study, using small interfering RNA-mediated silencing of 3BP2 in the RAW264.7 monocytic cell line, we show that 3BP2 was required for receptor activator of NFkappaB ligand (RANKL)-induced differentiation of RAW264.7 cells into multinucleated mature osteoclasts but not for granulocyte macrophage-colony stimulating factor/interleukin-4-induced differentiation into dendritic cells. 3BP2 silencing was associated with impaired activation of multiple signaling events downstream of RANK, including actin reorganization; Src, ERK, and JNK phosphorylation; and up-regulation of osteoclastogenic factors. In addition, 3BP2 knockdown cells induced to osteoclast by RANKL displayed a reduced increase of Src and nuclear factor of activated T cells (NFATc1) mRNA and protein expression. Importantly, 3BP2 interacted with Src, Syk, Vav, and Cbl in monocytic cells, and the introduction of constitutively active mutants of Src and NFATc1 in 3BP2-deficient cells restored osteoclast differentiation. Finally, the expression of a 3BP2 cherubism mutant was found to promote increased Src activity and NFAT-dependent osteoclast formation. Together, this study demonstrates that wild type 3BP2 is a key regulator of RANK-mediated macrophage differentiation into osteoclast through Src and NFATc1 activation.

Hypothalamic Injection of Oxyntomodulin Suppresses Circulating Ghrelin-Like Immunoreactivity

Ghrelin is a gastric peptide that regulates appetite and GH secretion. Circulating ghrelin levels are elevated by fasting and suppressed postprandially. However, the mechanisms regulating circulating ghrelin levels are unclear. Oxyntomodulin is an anorexic peptide hormone released from L cells in the gut. We investigated the effects of intracerebroventricular (icv) administration of oxyntomodulin on circulating ghrelin levels. The icv administration of 1, 3, or 10 nmol oxyntomodulin reduced circulating acylated and total (acylated and des-acylated) ghrelin 60 min after icv injection. Administration of 1 nmol oxyntomodulin directly into the arcuate nucleus of the hypothalamus significantly reduced total and acylated ghrelin levels, and administration of 3 nmol oxyntomodulin into the lateral ventricle induced c-fos mRNA expression in arcuate nucleus neurons expressing the glucagon-like peptide-1 (GLP-1) receptor. In a final study, the reduction in total ghrelin observed after icv injection of 3 nmol oxyntomodulin was blocked by coadministration of the GLP-1 receptor antagonist exendin (9-39). These studies suggest oxyntomodulin reduces peripheral ghrelin levels via GLP-1 receptor-dependent hypothalamic pathways. Postprandial release of anorexic gut hormones may thus act centrally to contribute to the postprandial reduction in circulating ghrelin.

Signal transduction and functional selectivity of F15599, a preferential post‐synaptic 5‐HT1A receptor agonist

Activation of post-synaptic 5-HT(1A) receptors may provide enhanced therapy against depression. We describe the signal transduction profile of F15599, a novel 5-HT(1A) receptor agonist. F15599 was compared with a chemical congener, F13714, and with (+)8-OH-DPAT in models of signal transduction in vitro and ex vivo. F15599 was highly selective for 5-HT(1A) receptors in binding experiments and in [(35)S]-GTPgammaS autoradiography of rat brain, where F15599 increased labelling in regions expressing 5-HT(1A) receptors. In cell lines expressing h5-HT(1A) receptors, F15599 more potently stimulated extracellular signal-regulated kinase (ERK1/2) phosphorylation, compared with G-protein activation, internalization of h5-HT(1A) receptors or inhibition of cAMP accumulation. F13714, (+)8-OH-DPAT and 5-HT displayed a different rank order of potency for these responses. F15599 stimulated [(35)S]-GTPgammaS binding more potently in frontal cortex than raphe. F15599, unlike 5-HT, more potently and efficaciously stimulated G(alphai) than G(alphao) activation. In rat prefrontal cortex (a region expressing post-synaptic 5-HT(1A) receptors), F15599 potently activated ERK1/2 phosphorylation and strongly induced c-fos mRNA expression. In contrast, in raphe regions (expressing pre-synaptic 5-HT(1A) receptors) F15599 only weakly or did not induce c-fos mRNA expression. Finally, despite its more modest affinity in vitro, F15599 bound to 5-HT(1A) receptors in vivo almost as potently as F13714. F15599 showed a distinctive activation profiles for 5-HT(1A) receptor-mediated signalling pathways, unlike those of reference agonists and consistent with functional selectivity at 5-HT(1A) receptors. In rat, F15599 potently activated signalling in prefrontal cortex, a feature likely to underlie its beneficial effects in models of depression and cognition.

Pituitary Adenylate Cyclase-Activating Polypeptide Inhibits Food Intake in Mice Through Activation of the Hypothalamic Melanocortin System

Pituitary adenylate cyclase-activating polypeptide (PACAP) and the proopiomelanocortin (POMC)-derived peptide, alpha-melanocyte-stimulating hormone (alpha-MSH), exert anorexigenic activities. While alpha-MSH is known to inhibit food intake and stimulate catabolism via activation of the central melanocortin-receptor MC4-R, little is known regarding the mechanism by which PACAP inhibits food consumption. We have recently found that, in the arcuate nucleus of the hypothalamus, a high proportion of POMC neurons express PACAP receptors. This observation led us to investigate whether PACAP may inhibit food intake through a POMC-dependent mechanism. In mice deprived of food for 18 h, intracerebroventricular administration of PACAP significantly reduced food intake after 30 min, and this effect was reversed by the PACAP antagonist PACAP6-38. In contrast, vasoactive intestinal polypeptide did not affect feeding behavior. Pretreatment with the MC3-R/MC4-R antagonist SHU9119 significantly reduced the effect of PACAP on food consumption. Central administration of PACAP induced c-Fos mRNA expression and increased the proportion of POMC neuron-expressing c-Fos mRNA in the arcuate nucleus. Furthermore, PACAP provoked an increase in POMC and MC4-R mRNA expression in the hypothalamus, while MC3-R mRNA level was not affected. POMC mRNA level in the arcuate nucleus of PACAP-specific receptor (PAC1-R) knock-out mice was reduced as compared with wild-type animals. Finally, i.c.v. injection of PACAP provoked a significant increase in plasma glucose level. Altogether, these results indicate that PACAP, acting through PAC1-R, may inhibit food intake via a melanocortin-dependent pathway. These data also suggest a central action of PACAP in the control of glucose metabolism.

Histamine enhances the production of human β-defensin-2 in human keratinocytes

The anti-microbial peptide human beta-defensin-2 (hBD-2), produced by epidermal keratinocytes, plays pivotal roles in anti-microbial defense, inflammatory dermatoses, and wound repair. hBD-2 induces histamine release from mast cells. We examined the in vitro effects of histamine on hBD-2 production in normal human keratinocytes. Histamine enhanced TNF-alpha- or IFN-gamma-induced hBD-2 secretion and mRNA expression. Histamine alone enhanced transcriptional activities of NF-kappaB and activator protein-1 (AP-1) and potentiated TNF-alpha-induced NF-kappaB and AP-1 activities or IFN-gamma-induced NF-kappaB and STAT1 activities. Antisense oligonucleotides against NF-kappaB components p50 and p65, AP-1 components c-Jun and c-Fos, or H1 antagonist pyrilamine suppressed hBD-2 production induced by histamine plus TNF-alpha or IFN-gamma. Antisense oligonucleotide against STAT1 only suppressed hBD-2 production induced by histamine plus IFN-gamma. Histamine induced serine phosphorylation of inhibitory NF-kappaBalpha (IkappaBalpha) alone or together with TNF-alpha or IFN-gamma. Histamine induced c-Fos mRNA expression alone or together with TNF-alpha, whereas it did not further increase c-Jun mRNA levels enhanced by TNF-alpha. Histamine induced serine phosphorylation of STAT1 alone or together with IFN-gamma, whereas it did not further enhance IFN-gamma-induced tyrosine phosphorylation of STAT1. The histamine-induced serine phosphorylation of STAT1 was suppressed by MAPKK (MEK) inhibitor PD98059. These results suggest that histamine stimulates H1 receptor and potentiates TNF-alpha- or IFN-gamma-induced hBD-2 production dependent on NF-kappaB, AP-1, or STAT1 in human keratinocytes. Histamine may potentiate anti-microbial defense, skin inflammation, and wound repair via the induction of hBD-2.

Induction of c-fos mRNA Expression by Pure Pressure Overload in Cultured Cardiac Myocytes

Mechanical stress by pressure overload due to hypertension or valvular heart disease such as aortic valve stenosis induces cardiac hypertrophy. It has been well established that the mechanical stretch of cardiac myocytes in vitro induces hypertrophic responses such as the expression of immediate early response genes including c-fos. However, it remains uncertain whether the mechanical forces due to pure atmospheric pressure can induce similar responses in cardiac myocytes. We thus cultured rat neonatal cardiac myocytes in an atmospheric pressure chamber apparatus and determined the effects of pure pressure stress on c-fos gene expression. Pressures greater than 80 mmHg enhanced c-fos mRNA after 30 minutes. These results suggest that pure atmospheric pressure overload can also induce early hypertrophic responses in cardiac myocytes.

Identification of Dopamine, Gonadotrophin‐Releasing Hormone‐I, and Vasoactive Intestinal Peptide Neurones Activated by Electrical Stimulation to the Medial Preoptic Area of the Turkey Hypothalamus: A Potential Reproductive Neuroendocrine Circuit

The neural and neurochemical substrates regulating reproduction in birds remain vaguely defined. The findings that electrical stimulation in the medial preoptic area (ES/MPOA) or intracerebroventricular infusion of dopamine (DA) stimulated luteinising hormone (LH) and prolactin (PRL) release in female turkeys, led to the suggestion that ES/MPOA might help to clarify the DA circuitry regulating LH and PRL. We used c-fos mRNA and tyrosine hydroxylase immunoreactivity as measured by double in situ hybridisation/immunocytochemistry (ISH/ICC) to determine which group/subgroup of DA neurones was activated following unilateral ES/MPOA. To establish that the reproductive neuroendocrine system was activated, double ISH/ICC was also conducted on c-fos/gonadotrophin-releasing hormone-I (GnRH-I) and c-fos/vasoactive intestinal peptide (VIP). Changes in circulating LH and PRL were determined by radioimmunoassay. Unilateral ES/MPOA (100 microA, right side) of anaesthetised laying turkeys for 30 min increased circulating LH and PRL levels. It also induced c-fos mRNA expression on the ipsilateral side by all GnRH-I neurones within the septopreoptic region, implying that GnRH-I neurones in this region share similar circuitry. VIP neurones within the nucleus infundibularis were the only VIP group to show c-fos mRNA expression, suggesting their involvement in ES/MPOA induced PRL release. c-fos mRNA expression was also observed in a subgroup of DA neurones in the nucleus mamillaris lateralis (ML). To our knowledge, the present study is the first to show that activation of DAergic cells in the ML is associated with the activation of GnRH-I and VIP neurones and the release of LH and PRL. It is likely that ES/MPOA activated VIP/GnRH-I neurones via activation of DA neurones in the ML, as this was the only DA subgroup that showed c-fos mRNA expression.

Activation of AMP-Activated Protein Kinase Enhances Angiotensin II–Induced Proliferation in Cardiac Fibroblasts

AMP-activated kinase (AMPK) is a highly conserved heterotrimeric kinase that functions as a metabolic regulator of cellular enzymes involved in carbohydrate and fat metabolism, which regulate ATP conservation and synthesis. Here, we investigated whether AMPK signaling has a role in the regulation of angiotensin II (Ang II)-induced proliferation in rat cardiac fibroblasts. Aminoimidazole-4-carboxamide-1-beta-ribofuranoside (AICAR) activated AMPK in rat cardiac fibroblasts and increased Ang II-induced extracellular signal-regulated kinase 1/2 phosphorylation and activity. AICAR also increased Ang II-induced c-fos mRNA expression in the cells. [3H]-thymidine and [3H]-proline incorporation by cardiac fibroblasts treated with Ang II was enhanced when the cells were pretreated with AICAR. Inhibition of AMPK by small interfering RNA for AMPKalpha1 suppressed Ang II-induced extracellular signal-regulated kinase activity, c-fos mRNA expression, and cell proliferation. Treatment of rats with AICAR (1 mg/g body weight per day) for 1 week significantly enhanced Ang II-induced hypertrophy of the myocardium. Our findings indicate that AMPK works as a stimulator of the Ang II-induced proliferative pathway in cardiac fibroblasts. Inhibition of AMPK signaling might serve as a new therapeutic target of remodeling of the hypertrophic myocardium.

Gastric Mucosal Protection: From Prostaglandins to Gene-Therapy

The maintenance of gastric mucosal function and integrity highly depends on the status of microcirculation. Vasoactive agents--prostaglandins, nitric oxide and sensory neuropeptides (e.g. calcitonin gene-related peptide)--play a crucial role in mucosal defensive processes. Beside the local release of vasoactive mediators the central nervous system is also involved in regulation of gastric functions. Cerebral lesions, stimulation of different brain areas can result in gastric mucosal injury. Noxious challenge of gastric mucosa alters the sodium currents in gastric sensory neurons and induces cfos mRNA expression in nucleus tractus solitarii and area postrema. Vagal nerve has long been established to play a permissive role in the development of gastric lesions. However, several lines of evidences suggest its physiological relevance in the enhancement of gastric mucosal resistance. It was concluded that gastroprotection can be induced by low level of central vagal stimulation and the consequent release of prostaglandins, nitric oxide, and calcitonin gene-related peptide. Prostaglandins, nitric oxide and sensory neuropeptides play a role also in ulcer healing by stimulating the formation of growth factors, the epithelial proliferation and angiogenesis. Both systemic and local administration of growth factors accelerated the ulcer healing. Local, single injection of plasmid-DNA encoding vascular endothelial growth factor (VEGF) was shown to stimulate the ulcer healing in the rat. The transient, local expression of VEGF in ulcerated tissue might be a new therapeutic strategy in the treatment of gastric ulcer disease.

The Induction of Prostaglandin E2 Production, Interleukin-6 Production, Cell Cycle Arrest, and Cytotoxicity in Primary Oral Keratinocytes and KB Cancer Cells by Areca Nut Ingredients Is Differentially Regulated by MEK/ERK Activation

There are about 200-600 million betel quid (BQ) chewers in the world. BQ chewing is one of the major risk factor of hepatocarcinoma, oropharyngeal, and esophagus cancers in Taiwan, India, and Southeast Asian countries. Thus, the precise molecular mechanisms deserve investigation. We used cultured primary keratinocytes and KB cells, RT-PCR, flow cytometry, Western blotting, and ELISA to evaluate whether alterations in early gene expression is crucial in the carcinogenic processes of BQ. We observed the induction of c-Fos mRNA expression in human gingival keratinocyte (GK) and KB carcinoma cells by areca nut (AN) extract and arecoline. A maximal increment in c-fos gene expression was shown at about 30 min after challenge. AN extract (100-800 microg/ml) and arecoline (0.1-0.8 mM) also stimulated ERK1/ERK2 phosphorylation with a maximal stimulation at 5-10 min of exposure. Pretreatment by U0126 (30 microM), a MEK inhibitor, markedly inhibited the c-Fos, cyclooxygenase-2 (COX-2), and IL-6 mRNA expression of the KB epithelial cells. In addition, U0126 and PD98059 (50 microM) also decreased AN extract- and arecoline-associated PGE2 and IL-6 production in GK and KB cells. However, U0126 by itself arrested the cells in G0/G1 phase, but was not able to prevent AN- and arecoline-induced cell death or apoptosis. In contrast, U0126 enhanced the AN-induced apoptosis of KB cells. AN ingredients thus play a significant role in the pathogenesis of oropharyngeal cancer by activation of MEK1/ERK/c-Fos pathway, which promotes keratinocyte inflammation, cell survival, and affects cell cycle progression.

Effects of NMDA-Receptor Antagonist Treatment on c-fos Expression in Rat Brain Areas Implicated in Schizophrenia

1. The noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonists produce behavioral responses that closely resemble both positive and negative symptoms of schizophrenia. These drugs also induce excitatory and neurotoxic effects in limbic cortical areas. 2. We have here mapped the brain areas which show increased activity in response to noncompetitive NMDA-receptor antagonist administration concentrating especially to those brain areas that have been suggested to be relevant in the pathophysiology of schizophrenia. 3. Rats were treated intraperitoneally with a NMDA-receptor antagonist MK801 and activation of brain areas was detected by monitoring the expression of c-fos mRNA by using in situ hybridization. 4. MK801 induced c-fos mRNA expression of in the retrosplenial, entorhinal, and prefrontal cortices. Lower c-fos expression was observed in the layer IV of the parietal and frontal cortex. In the thalamus, c-fos mRNA expression was detected in the midline nuclei and in the reticular nucleus but not in the dorsomedial nucleus. In addition, c-fos mRNA was expressed in the anterior olfactory nucleus, the ventral tegmental area, and in cerebellar granule neurons. 5. NMDA-receptor antagonist ketamine increased dopamine release in the parietal cortex, in the region where NMDA-receptor antagonist increased c-fos mRNA expression. 6. Thus, the psychotropic NMDA-receptor antagonist induced c-fos mRNA expression in most, but not all, brain areas implicated in the pathophysiology of schizophrenia. The high spatial resolution of in situ hybridization may help to define regions of interest for human imaging studies.

C-fos and CRF receptor gene transcription in the brain of acetic acid-induced somato-visceral pain in rats

We aimed to characterize neuronal and corticotrophin-releasing (CRF) pathways in a model of somato-visceral pain in rats. Male rats received an intraperitoneal (i.p.) injection of either vehicle (controls) or acetic acid (AA) and were sacrificed 1, 2, 3, 4, or 6 h later. Coronal frozen sections of the brain were cut and mRNAs encoding the rat c-fos, CRF 1, CRF 2α,β receptors were assayed by in situ hybridisation histochemistry. Localization of these transcripts within CRF-immunoreactive (i.r.) neurons of the paraventricular nucleus (PVN) of the hypothalamus was also determined. AA i.p. induced c-fos mRNA expression in brain nuclei involved in the autonomic, behavioural and neuroendocrine response to pain. Some of these nuclei are involved in the control of digestive motility, as represented by the PVN, locus coeruleus and nucleus tractus solitarius. CRF pathways, in particular in the PVN, are activated in this model. Indeed, a robust signal of c-fos and CRF 1 transcripts was observed in the PVN and numerous CRF-i.r. neurons expressed c-fos or CRF 1 transcripts in the PVN of AA-treated animals. In contrast, no expression of CRF 2 transcripts was observed in the PVN either in basal conditions or after AA i.p. These data argue for an activation of CRF pathways within the PVN in this model of somato-visceral pain. The use of CRF antagonists, particularly of the CRF 1 type, should have an interest in somato-visceral pain pathology.

Effects of granisetron and vagotomy on c-fos mRNA expression in the rat medulla oblongata as assessed by in situ hybridization

Cancer chemotherapy-induced nausea and vomiting have been demonstrated to involve humoral as well as neuronal mechanisms. A leading role of serotonin (5-hydroxytryptamine, 5-HT) in these mechanisms is supported by inhibition of the emesis by 5-HT3 receptor antagonists. We compared the effects of granisetron, a selective 5-HT3 receptor antagonist, and vagotomy on c-fos mRNA expression in the nucleus of the solitary tract (NTS) and the area postrema (AP) of the rat caudal brainstem by means of in situ hybridization. The expression of c-fos mRNA in the NTS and AP was significantly elevated 2 h after cisplatin administration. The induction of c-fos expression by cisplatin in the NTS was significantly inhibited by pretreatment with granisetron. In contrast, the c-fos expression in the AP did not differ between the cisplatin group and the granisetron-treated cisplatin group. The degree of the induction of c-fos mRNA expression in both the AP and NTS was similar between the vagotomy and sham operation groups. Our results suggest that the expression of c-fos mRNA in the NTS may be specifically controlled by 5-HT3 receptors and that nonspecific humoral factors, such as modulation of transcriptional activity, play an important role in c-fos expression in the AP after vagotomy.