Innervation of histamine neurons in the caudal part of the arcuate nucleus of hypothalamus and their activation in response to food deprivation under scheduled feeding.

It has been well established that histaminergic neurons innervate densely the anterior hypothalamus and regulate several functions through the histamine H1 receptor (H1R). However, the physiological function of the histaminergic neurons in other regions including the posterior hypothalamus has not been fully investigated. Recently, we have found a selective c-Fos expression in the caudal part of the arcuate nucleus of the hypothalamus (cARC) by food deprivation under scheduled feeding in rats. In this study, we histochemically examined the correlation of this c-Fos expression with the activation of histaminergic neurons in this region using an anti-H1R antibody. Strong H1R immunoreactivity was observed in the perikarya of the c-Fos positive cells. Abundant histamine-containing fibers were also found in the cARC and in the area between the cARC and the tuberomammillary nucleus (TM), where the histaminergic neuronal cell bodies are exclusively distributed. Our morphological observations suggest that c-Fos expression in the cARC by food deprivation under scheduled feeding is caused by the activation of histaminergic neurons projected from the TM.

The forkhead transcription factors, Foxp1 and Foxp2, identify different subpopulations of projection neurons in the mouse cerebral cortex.

Foxp1 and Foxp2, which belong to the forkhead transcription factor family, are expressed in the developing and adult mouse brain, including the striatum, thalamus, and cerebral cortex. Recent reports suggest that FOXP1 and FOXP2 are involved in the development of speech and language in humans. Although both Foxp1 and Foxp2 are expressed in the neural circuits that mediate speech and language, including the corticostriatal circuit, the functions of Foxp1 and Foxp2 in the cerebral cortex remain unclear. To gain insight into the functions of Foxp1 and Foxp2 in the cerebral cortex, we characterized Foxp1- and Foxp2-expressing cells in postnatal and adult mice using immunohistochemistry. In adult mice, Foxp1 was expressed in neurons of layers III-VIa in the neocortex, whereas the expression of Foxp2 was restricted to dopamine and cyclic adenosine 3',5'-monophosphate-regulated phosphoprotein, 32 kDa (DARPP-32)(+) neurons of layer VI. In addition, Foxp2 was weakly expressed in the neurons of layer V of the motor cortex and hindlimb and forelimb regions of the primary somatosensory cortex. Both Foxp1 and Foxp2 were expressed in the ionotropic glutamate receptor (GluR) 2/3(+) neurons, and colocalized with none of GluR1, gamma-aminobutyric acid, calbindin, and parvalbumin, indicating that expression of Foxp1 and Foxp2 is restricted to projection neurons. During the postnatal stages, Foxp1 was predominantly expressed in Satb2(+)/Ctip2(-) corticocortical projection neurons of layers III-V and in Tbr1(+) corticothalamic projection neurons of layer VIa. Although Foxp2 was also expressed in Tbr1(+) corticothalamic projection neurons of layer VI, no colocalization of Foxp1 with Foxp2 was observed from postnatal day (P) 0 to P7. These findings suggest that Foxp1 and Foxp2 may be involved in the development of different cortical projection neurons during the early postnatal stages in addition to the establishment and maintenance of different cortical circuits from the late postnatal stage to adulthood.

Characterization of Foxp2-expressing cells in the developing spinal cord.

Two members of winged-helix/forkhead transcription factors, Foxp1 and Foxp2, are expressed in the developing and adult CNS, including the striatum, cerebral cortex, and thalamus. In a previous study, we have demonstrated that Foxp1 is expressed in a subpopulation of V1 interneurons in addition to motor neurons of the spinal cord during mouse embryogenesis. However, the detailed expression pattern of Foxp2 and its relationship with Foxp1 in the developing spinal cord remains to be elucidated. To shed light on the potential roles of Foxp1 and Foxp2 in the developing spinal cord, we characterized Foxp2-expressing cells during mouse embryogenesis. At embryonic day (E) 11.0, Foxp2-expressing cells were first observed in the ventral spinal cord, which were Pax6(-), p27(+), and neuron-specific class III beta-tubulin(+) postmitotic neurons. Between E13.5 and E15.5, high expression of Foxp2 was observed in both medial and lateral parts of the ventral spinal cord. Double-immunofluorescence staining for Foxp2 with some homeodomain transcription factors revealed that Foxp2-expressing neurons were Pax2(+), En1(+), Evx1(-), Chx10(-), Gata3(-), and Lhx3(-) V1 interneurons in the intermediate zone throughout the ventral spinal cord, indicating that Foxp2-expressing neurons were also V1 interneurons with the same phenotypes as Foxp1-expressing interneurons. In addition, neither Foxp1 nor Foxp2 was expressed in ventral calbindin(+) Renshaw cells. However, Foxp2 did not colocalize with Foxp1 in interneurons of the ventral spinal cord. These findings suggest that Foxp1 and Foxp2 are expressed in the distinct subsets of V1 interneurons that belong to non-Renshaw cells in the ventral spinal cord during embryogenesis. Thus, Foxp1 and Foxp2 may be involved in the determination of the cell type identities during late embryogenesis: the classes of neurotransmitters and the functional subtypes of non-Renshaw cells, such as Ia and Ib inhibitory interneurons.

Expression of mKirre in the developing sensory pathways: its close apposition to nephrin-expressing cells.

mKirre is a novel member of the immunoglobulin superfamily, which is abundant in the developing and adult brain. In the present study, we showed mKirre gene expression in mouse sensory organs during development using in situ hybridization and immunohistochemistry. At embryonic day (E) 11.5, E15.5, and E17.5, we first detected signals for mKirre mRNA in the developing cochleae, retinae, and olfactory neuroepithelia, respectively. After birth, strong signals were observed in these sensory organs. In addition, at this stage, we found its expression in trigeminal ganglion neurons and neuronal populations forming sensory pathways in the olfactory bulb, midbrain, and pons. Furthermore, double-immunofluorescence staining revealed that nephrin-immunoreactivity was overlapping to mKirre-expressing cells in the developing sensory organs. These results suggest that mKirre may be involved in the establishment of the pathway from sensory organs to the brain not only in a homophilic manner but also with its heterophilic interaction to nephrin.

Activation of central 5HT2A receptors reduces the craniofacial nociception of rats.

We assessed the contribution of central 5HT2A receptors to the craniofacial tissue nociception in naïve male rats. First, we tested whether activation of central 5HT2A receptors affected nociceptive neural activities recorded from superficial laminae of the trigeminal subnucleus caudalis (Vc)/upper cervical spinal cord junction (Vc/C2) region. Two types of units, such as deep-nociceptive or skin-wide dynamic range (WDR) units were identified from extracellular recordings. Topical administration of 5HT2A receptor agonist, (+/-)-2,5-dimethoxy-4-iodoamphetamine (DOI) onto the Vc/C2 region significantly reduced deep-nociceptive unit discharges evoked by formalin injection into the masseter muscle. Noxious pinch stimulation to the facial skin-evoked skin-WDR unit discharges was significantly reduced by topical administration of 0.1 mg/rat DOI onto the Vc/C2 region. Second, we tested whether i.c.v. administration of DOI affected Fos-like immunoreactivity (-LI) evoked by formalin injection into the masseter muscle. Fos-LI was significantly induced mainly at the ventrolateral (vl) area of trigeminal subnucleus interpolaris (Vi)/Vc junction (vl-Vi/Vc) region and Vc/C2 region in vehicle-treated rats. Formalin-evoked Fos-LI was significantly reduced in laminae I-II of the Vc/C2, but not vl-Vi/Vc region after i.c.v. administration of DOI. Finally, orofacial nocifensive behavioral activities evoked by formalin injection into the masseter muscle were significantly reduced by intracisternal administration of DOI. These results suggest that 5HT2A receptors in the Vc/C2 region mediate antinociceptive effects in the craniofacial nociception.

Contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus produced by acute injury to the masseter muscle during persistent temporomandibular joint inflammation in rats.

We investigated the contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus (VSP) following acute masseter muscle injury in male rats with or without temporomandibular joint (TMJ) inflammation persisting for 7 days. TMJ inflammation was evoked by an injection of complete Freund's adjuvant (CFA). Two hours after formalin injection into the masseter muscle produced Fos-like immunoreactivity (Fos-LI) in several regions of the VSP and upper cervical spinal cord (C2), such as ventrolateral (vl) area of the trigeminal subnucleus caudalis (Vc)/subnucleus interpolaris (Vi) transition (vl-Vi/Vc), paratrigeminal nucleus (dPa5), middle portion of the Vc (mid-Vc) and Vc/C2 transition (Vc/C2) regions in both groups. Significant increases in the number of Fos-LI were observed in these areas in CFA group compared with non-CFA group. TMJ inflammation alone did not induce a significant level of Fos-LI in the VSP. In order to assess the effect of antagonizing 5-HT2A or 5-HT3 receptors on formalin-induced Fos-LI, rats were pre-treated with local (masseter muscle) administration of ketanserin or tropisetron (0.01, 0.1 mg/rat) 20 min prior to formalin injection. In CFA group, these antagonists given locally reduced the Fos-LI response in the laminae I-II at the mid-Vc and Vc/C2 regions. These antagonists reduced the Fos-LI response in the dPa5, but not in the vl-Vi/Vc region. The Fos-LI response was not affected by i.v. administration of ketanserin (0.01, 0.1 mg/rat) or tropisetron (0.01 mg/rat). In non-CFA group, these antagonists given locally did not reduce the Fos-LI response. These results suggest that peripheral 5-HT2A and 5-HT3 receptors contribute to nociceptive processing in the masseter muscle in TMJ inflammatory conditions.

Complete overlap of interleukin-31 receptor A and oncostatin M receptor beta in the adult dorsal root ganglia with distinct developmental expression patterns.

Interleukin-31 receptor A (IL-31RA) is a newly identified type I cytokine receptor, that is related to gp130, the common receptor of the interleukin (IL) -6 family cytokines. Recent studies have shown that IL-31RA forms a functional receptor complex for IL-31 together with the beta subunit of oncostatin M receptor (OSMRbeta). However, little is known about the target cells of IL-31 because it remains unclear which types of cells express IL-31RA. In our previous reports, we demonstrated that OSMRbeta is expressed in a subset of small-sized nociceptive neurons of adult dorsal root ganglia (DRGs). In the present study, we investigated the IL-31RA expression in the adult and developing DRGs. From a northern blot analysis and in situ hybridization histochemistry, IL-31RA mRNA was found to be expressed in the adult DRGs. According to reverse-transcriptase polymerase chain reaction, IL-31RA mRNA was detected in the DRGs and trigeminal ganglia, while no expression of IL-31RA mRNA was observed in the CNS. Double immunofluorescence staining revealed IL-31RA to be expressed in a subset of small-sized neurons, all of which colocalized with OSMRbeta. In addition, the expression of IL-31 RA was detected in afferent fibers in the spinal cord and the dermis of the skin. We also found that the developmental expression pattern of IL-31RA was different from that of OSMRbeta; IL31RA-positive neurons in DRGs first appeared at postnatal day (PN) 10 and reached the adult level at PN14, whereas OSMRbeta-positive neurons were observed at PN0 for the first time. We previously demonstrated OSMRbeta-expressing neurons to decrease, however, they were not found to disappear in oncostatin M (OSM) -deficient mice. These findings suggest that IL-31 and OSM may thus have redundant functions in the development of OSMRbeta-expressing neurons.

Induction of brain-derived neurotrophic factor by leptin in the ventromedial hypothalamus.

Leptin, an adipocyte-derived hormone, reduces food intake by regulating orexigenic and anorexigenic factors in the hypothalamus. Although brain-derived neurotrophic factor is an important anorexigenic factor in the hypothalamus, little is known about the regulation of brain-derived neurotrophic factor expression by leptin in the hypothalamus. In the present study, we examined the effect of leptin on the expression of brain-derived neurotrophic factor in the hypothalamus. I.V. administration of leptin (10 microg/g) led to the increase in the expression of brain-derived neurotrophic factor mRNA, which was observed in the dorsomedial part of the ventromedial hypothalamic nucleus. The increased expression of brain-derived neurotrophic factor mRNA was detected in phosphorylated signal transducer and activator of transcription 3-positive neurons, suggesting that leptin induced brain-derived neurotrophic factor expression in neurons of the dorsomedial part of the ventromedial hypothalamic nucleus. In addition, the expression of brain-derived neurotrophic factor was increased at the protein level in the ventromedial hypothalamic nucleus of leptin-injected mice. Interestingly, brain-derived neurotrophic factor-positive fibers also increased in the ventromedial hypothalamic nucleus and dorsomedial hypothalamic nucleus of leptin-injected mice, which were in close apposition to tyrosine kinase receptor B-immunoreactive neurons and colocalized with synaptophysin, a marker of presynaptic terminals. These results suggest that leptin induces brain-derived neurotrophic factor expression in the dorsomedial part of the ventromedial hypothalamic nucleus and brain-derived neurotrophic factor may exert as anorexigenic factors possibly through the activation of tyrosine kinase receptor B in the ventromedial hypothalamic nucleus and dorsomedial hypothalamic nucleus.

Central serotonin 3 receptors play an important role in the modulation of nociceptive neural activity of trigeminal subnucleus caudalis and nocifensive orofacial behavior in rats with persistent temporomandibular joint inflammation.

The role of central serotonin 3 receptors on neural activities recorded from superficial laminae of trigeminal subnucleus caudalis/upper cervical spinal cord junction region was investigated using rats with (Complete Freund's Adjuvant day 7 group) or without (non-Complete Freund's Adjuvant group) persistent temporomandibular joint inflammation evoked by Complete Freund's Adjuvant for 7 days. We identified two types of units, Deep-wide dynamic range units and Skin-wide dynamic range units from extracellular recordings. Deep-wide dynamic range units have mechanoreceptive fields in the deep craniofacial tissues including masseter muscle but do not have cutaneous mechanoreceptive fields. Deep-wide dynamic range unit discharges evoked by the formalin injection into masseter muscle were significantly enhanced in the late phase in Complete Freund's Adjuvant day 7 group. Discharges of Skin-wide dynamic range units evoked by the noxious pinch stimulation to facial skin in Complete Freund's Adjuvant day 7 group were significantly enhanced compared with those in non-Complete Freund's Adjuvant group. Topical administration of central serotonin 3 receptor antagonist, tropisetron, onto trigeminal subnucleus caudalis/upper cervical spinal cord junction region significantly reduced both formalin-evoked Deep-wide dynamic range unit and pinch-evoked Skin-wide dynamic range unit discharges in non-Complete Freund's Adjuvant and Complete Freund's Adjuvant day 7 groups significantly. The inhibitory effects of tropisetron on pinch-evoked Skin-wide dynamic range unit discharges were prolonged in Complete Freund's Adjuvant day 7 group compared with those in non-Complete Freund's Adjuvant group. The role of central serotonin 3 receptors in trigeminal subnucleus caudalis/upper cervical spinal cord junction region was also tested by orofacial formalin test in Complete Freund's Adjuvant day 7 group. Intracisternal administration of tropisetron decreased the orofacial nocifensive behavior in the late phase evoked by the injection of formalin into the masseter muscle. These results suggest that central serotonin 3 receptors in trigeminal subnucleus caudalis/upper cervical spinal cord junction region are involved in mediating pronociceptive effects in both superficial and deep craniofacial tissues nociception during persistent temporomandibular joint inflammation.

Up-regulated phosphorylation of signal transducer and activator of transcription 3 and cyclic AMP-responsive element binding protein by peripheral inflammation in primary afferent neurons possibly through oncostatin M receptor.

Oncostatin M (OSM), a member of interleukin-6 family cytokines, contributes to the development of nociceptive sensory neurons. However, little is known about the role of OSM in dorsal root ganglia (DRGs) of adult mice after peripheral inflammation. In the present study, we showed that OSM mRNA was highly expressed in the inflamed skin during acute inflammation induced by complete Freund's adjuvant (CFA), while the expression of oncostatin M receptor (OSMR) did not change in the ipsilateral DRG. Although peripheral inflammation induced significant increases in the number of neurons with phosphorylated extracellular signal-regulated kinase (p-ERK) and phosphorylated p38 mitogen-activated protein kinase (p-p38) in ipsilateral DRGs, OSMR-positive neurons exhibited neither p-ERK nor p-p38. In addition, we found significant increases in the number of neurons with phosphorylated signal transducer and activator of transcription 3 (p-STAT3) and phosphorylated cAMP-responsive element binding protein (p-CREB) in the ipsilateral DRGs. Interestingly, OSMR-positive neurons with p-STAT3 and p-CREB were significantly increased after peripheral inflammation. Thus, our results suggest that acute inflammation induce the phosphorylations of several signal molecules, including ERK, p38, cAMP-responsive element binding protein, and STAT3. Among them, the up-regulation of p-STAT3 and p-CREB may be induced possibly through OSMR.

Expression of mKirre, a mammalian homolog of Drosophila kirre, in the developing and adult mouse brain.

mKirre, a mammalian homolog of the Drosophila kirre, is expressed in bone marrow stromal cells and the brain. Although mKirre has been shown to support the hematopoietic stem cells, little is known about the function of mKirre in the brain. In the present study, to gain insights into the function of mKirre, we investigated the expression pattern of mKirre gene in the developing and adult mouse brain using in situ hybridization. In the adult brain, mKirre mRNA was highly expressed in the olfactory bulb, the piriform cortex, the cochlear nucleus, and the cerebellum. At embryonic day (E) 11.5, we could observe mKirre mRNA in the differentiating zones of various regions, such as the caudate-putamen, the geniculate body, the thalamus, the amygdala, and the brainstem. Its gene expression in these regions at E11.5 also persisted to the adult, in which its expression levels were much less prominent. After birth, we could first observe high expression of mKirre mRNA in the glomerular and mitral layers of the olfactory bulb, the cortical plate of the neocortex, the cochlear nucleus, and the molecular and granule cell layers of the cerebellum. In the hippocampus, its gene expression was first observed in the dentate gyrus at postnatal day 7. The spatiotemporal expression pattern of mKirre mRNA suggests important roles of mKirre in later developmental processes, especially the synapse formation.

The role of peripheral 5HT2A and 5HT1A receptors on the orofacial formalin test in rats with persistent temporomandibular joint inflammation.

The role of peripheral serotonin (5HT) 2A and 5HT1A receptors on the orofacial nocifensive behavioral activities evoked by the injection of formalin into the masseter muscle was evaluated in the rats with persistent temporomandibular joint (TMJ) inflammation evoked by Complete Freund's Adjuvant (CFA). The orofacial nocifensive behavioral activities evoked by the injection of formalin into masseter muscle were significantly enhanced at 1 day (CFA day 1 group) or 7 days (CFA day 7 group) during TMJ inflammation. Pretreatment with local administration of 5HT2A receptor antagonist, ketanserin (0.01, 0.1 mg/rat) into the masseter muscle or systemic administration of ketanserin via i.p. injection (1 mg/kg) reduced the orofacial nocifensive behavioral activities of the late phase evoked by formalin injection into masseter muscle on the side of TMJ inflammation (CFA day 7 group). However, local (0.001-0.1 mg/rat) or systemic (1 mg/kg) administration of 5HT1A receptor antagonist, propranolol, into masseter muscle did not produce the antinociceptive effect in CFA day 7 group. Moreover, local administration of ketanserin (0.1 mg) or propranolol (0.1 mg) into masseter muscle did not inhibit nocifensive orofacial behavior in rats without TMJ inflammation. These data suggest that persistent TMJ inflammation causes the elevation of the orofacial nocifensive behavior, and peripheral 5HT2A receptors play an important role in mediating the deep craniofacial tissue nociception in rats with TMJ inflammation.

TRPV2, a capsaicin receptor homologue, is expressed predominantly in the neurotrophin-3-dependent subpopulation of primary sensory neurons.

TRPV2, a member of transient receptor potential ion channels, responds to high-threshold noxious heat, but neither to capsaicin nor to proton. Although TRPV2 is expressed in medium- to large-sized dorsal root ganglion (DRG) neurons with myelinated fibers in adult rodents, little is known about the neurotrophin dependence of TRPV2-positive neurons in the developing and adult DRGs of mice. In the present study, using immunohistochemistry, we found that TRPV2 was first expressed in DRG neurons at embryonic day (E) 11.5, when neither TRPV1 nor TRPM8 was detected yet. Double-immunofluorescence staining revealed that tyrosine kinase receptor C (TrkC) was expressed in most of TRPV2-positive DRG neurons at E11.5 and E13.5. In addition, the percentage of TRPV2-positive neurons in the total DRG neurons at E13.5 reached the same as that of adulthood. In adult DRGs, TrkC and Ret were expressed in 68% and 25% of TRPV2-positive neurons, respectively. These results suggest that TRPV2 is expressed predominantly in the NT-3-dependent subpopulation of DRG neurons throughout development and in adult mice.

Foxp1 gene expression in projection neurons of the mouse striatum.

The developmental processes of maturation in the CNS are the result of specific events including mitogenesis, differentiation, and cell death which occur in a precise spatial and temporal manner. It has been reported that many transcription factors, including forkhead transcription factors, play a key role in these processes. First, we examined the expression pattern of the forkhead transcription factor Foxp1 in the adult CNS. Foxp1 was highly expressed in the striatum and moderately in the cerebral cortex, CA1/2 subfields of the hippocampus, and several thalamic nuclei. In situ hybridization combined with immunohistochemistry in the striatum of adult mice revealed that Foxp1 mRNA was detected in a subset of projection neurons, not in interneurons. In addition, the expression of Foxp1 mRNA was observed in the developing basal ganglia with the exception of the globus pallidus. Thus, Foxp1 mRNA was expressed in a subset of striatal projection neurons, probably the matrix neurons. The expression pattern of Foxp1 mRNA suggests that Foxp1 may play a role in the development and formation of a circuit in the basal ganglia, which is involving the matrix neurons.

Fasting-induced activation of mitogen-activated protein kinases (ERK/p38) in the mouse hypothalamus.

Activity-dependent changes in neuronal plasticity depend critically on gene regulation. To understand how fasting-induced stimulation leads to gene regulation through intracellular signalling pathways, we investigated the effect of fasting on activation of the mitogen-activated protein kinase (MAPK) family, the extracellular signal-regulated kinase (ERK) and the p38 MAPK (p38) in mouse hypothalamus. In the hypothalamic arcuate nucleus, phosphorylation of ERK significantly increased during fasting, spatially coincident with phosphorylation of cAMP response element binding protein (CREB), induction of c-Fos, and expression of neuropeptide Y (NPY). In the paraventricular nucleus (PVN) of fasted mice, activation of p38 in addition to ERK was also observed. In the arcuate nucleus of ob/ob mice, phosphorylations of ERK and CREB were decreased during fasting, whereas the expression of NPY was increased. In the PVN, increased activation of p38 was observed in spite of decreased activation of ERK. These results suggest that ERK and p38 are differentially activated by fasting in distinct regions of the hypothalamus depending on the condition of energy balance.

Localization of oncostatin M receptor beta in adult and developing CNS.

Oncostatin M (OSM) is a member of the interleukin-6 cytokine family, which is involved in definitive hematopoiesis, the development of liver, and local inflammation. However, little is known about the role of OSM in the murine CNS. Using Northern blot analysis, we examined the regional distribution of OSM receptor beta (OSMRbeta) mRNA in the adult CNS. OSMRbeta mRNA was observed predominantly in the olfactory bulb, and with low levels in the other regions. In situ hybridization shows that OSMRbeta gene expression was found in astrocytes of olfactory bulb, epithelial cells of choroid plexus, and meningeal cells in pia mater. In addition, we investigated the gene expression of OSMRbeta in the developing CNS at different time points. Its gene expression was first observed in large neurons of the hypoglossal nucleus at 14.5 days postcoitum, which was sustained until neonatal mice. OSMRbeta mRNA and protein were mainly localized in the ventral subnucleus of the developing hypoglossal nucleus. Our results suggest that OSM contributes to the development of specific subpopulations of both neurons and astrocytes in the murine CNS.

Distinct gene expression in the stomach following stress and alcohol exposure.

Two paradigms of acute stress in the rat were used to produce changes in the stomach. The first involved restraint stress combined with water immersion and the second utilized acute intragastric exposure to absolute ethanol. The mRNA expression of immediate early genes (IEG) such as c-fos, c-jun and NGFI-A, cyclooxygenase (COX)-2 and heat shock proteins (HSP) 70 in the stomach were studied using in situ hybridization histochemistry. Upregulation of IEG and HSP70 mRNAs were observed in the smooth muscle cells of muscularis mucosae, muscularis externa and blood vessels in response to water immersion-restraint stress or intragastric application of absolute ethanol. In the restraint stress model, IEG (c-fos and NGFI-A) mRNAs were induced in the pit and isthmus of the mucosa, while in the ethanol exposure model, IEG (c-fos, c-jun and NGFI-A) and HSP70 mRNAs were upregulated in the damaged epithelium, especially surrounding the deep erosions. COX-2 mRNA was detected in surface mucous cells under desquamation. These distinct gene expressions in the mucosa indicate that the two stress paradigms produce different cellular responses. These data provide new insights into cellular mechanisms that occur during the pathogenesis of acute gastric mucosal lesions.

Difference in binding by isolectin B4 to trkA and c-ret mRNA-expressing neurons in rat sensory ganglia.

The neurons labeled by isolectin B4 (IB4) in rat and mouse sensory ganglia are often regarded as non-nerve growth factor (NGF)-dependent and non-peptidergic neurons, but a considerable number of IB4-positive neurons in the dorsal root ganglion (DRG) are also shown to be immunoreactive to substance P (SP) and calcitonin gene-related peptide (CGRP), which are synthesized by NGF-dependent neurons. Therefore, we examined the relationships between the IB4-binding neurons and NGF/glial cell line-derived neurotrophic factor (GDNF)/GDNF-related proteins(GDNFs)-dependent neurons in rat DRGs by use of in situ hybridization histochemistry in serial sections. Of the DRG neurons, 42% and 22% were intensely and weakly labeled by IB4, respectively. The former neurons were small, and the latter varied in size. Of the trkA mRNA-expressing neurons, 29% and 57% were intensely and weakly labeled by IB4, respectively. On the other hand, 66% and 10% of the c-ret mRNA-expressing neurons were intensely and weakly labeled, respectively. The mRNA of somatostatin, another major neuropeptide in the sensory neurons, was exclusively expressed in the intensely IB4-labeled neurons. These findings suggest that many NGF-dependent and peptidergic sensory neurons are labeled by IB4 in rats.

Emotional stress activates MAP kinase in the rat heart.

Emotional stress evoked by immobilization of the rat induces c-fos mRNA or other immediate early genes. This response is mediated by activation of alpha- and beta-adrenoceptors, through mechanisms that have not yet been elucidated. Here we show that immobilization stress activates p44/p42 Mitogen-Activated Protein kinase (p44/p42 MAP kinase, Erk1/Erk2). Pretreatment with the beta1-blocker, metoprolol, did not inhibit the activation of stress-induced MAP kinase, while blockage of the alpha1-adrenoceptor by pretreatment with alpha1-blocker, prazosin or the alpha/beta-blocker, amosulalol, attenuated the activation. Application of the alpha1-agonist, phenylephrine, but not the beta-agonist, isoproterenol, to the perfused rat heart elicited MAP activation. Thus, emotional stress activates the alpha1-adrenoceptor-mediated MAP kinase pathway, whereas the pathway of the response mediated by the beta-adrenoceptor remains unknown.

[Primary sensory neurons expressing histamine H1-receptor mRNA].

Pharmacological studies have suggested that a subgroup of primary sensory neurons is responsive to histamine via the H1 receptor. However, which type of primary sensory neurons express H1 receptor is not known. We addressed this issue using in situ hybridization histochemistry with a cRNA probe for the guinea pig H1 receptor mRNA. H1 receptor mRNA was expressed in about 15-20% of the trigeminal and lumbar dorsal root ganglion (DRG) neurons, but none of the nodose ganglion neurons. The positive neurons in DRG were exclusively small in size and were labeled by isolectin B4, suggesting that these neurons have unmyelinated fibers. However, H1-receptor mRNA-expressing DRG neurons were not immunoreactive to substance P (SP) or calcitonin gene-related peptide (CGRP), which are implicated in the nociceptive transmission of the primary sensory system. Moreover, in guinea pigs neonatally treated with capsaicin (50 mg/kg), few CGRP-immunoreactive neurons were seen in DRG, but the percentage of H1-receptor mRNA-expressing neurons (15%-20%) and the intensity of the mRNA signals in these neurons were not affected by neonatal capsaicin treatment, suggesting that H1 receptor-expressing neurons are not sensitive to capsaicin. These findings suggest that H1-receptor-expressing neurons are involved in the transmission of a unique sensory modality such as itch. A marked increase in the number of mRNA-positive DRG neurons was observed 1-5 days after a crush injury of the sciatic nerve (3-4-fold of the control value). These neurons that turned mRNA-positive after the nerve crush were also mainly small-sized. The mRNA signals were detected in many peptidergic (SP/CGRP) neurons, in contrast to the normal condition. On the other hand, mRNA signals were decreased in the neurons that showed intense labeling in the normal condition. These results suggest that the gene expression of H1 receptors up-regulated in injured afferents may be involved in neuropathic pain.