Principal component analysis uncovers cytomegalovirus-associated NK cell activation in Ph+ leukemia patients treated with dasatinib.

Dasatinib treatment markedly increases the number of large granular lymphocytes (LGLs) in a proportion of Ph+ leukemia patients, which associates with a better prognosis. The lymphocytosis is predominantly observed in cytomegalovirus (CMV)-seropositive patients, yet detectable CMV reactivation exists only in a small fraction of patients. Thus, etiology of the lymphocytosis still remains unclear. Here, we identified NK cells as the dominant LGLs expanding in dasatinib-treated patients, and applied principal component analysis (PCA) to an extensive panel of NK cell markers to explore underlying factors in NK cell activation. PCA displayed phenotypic divergence of NK cells that reflects CMV-associated differentiation and genetic differences, and the divergence was markedly augmented in CMV-seropositive dasatinib-treated patients. Notably, the CMV-associated highly differentiated status of NK cells was already observed at leukemia diagnosis, and was further enhanced after starting dasatinib in virtually all CMV-seropositive patients. Thus, the extensive characterization of NK cells by PCA strongly suggests that CMV is an essential factor in the NK cell activation, which progresses stepwise during leukemia and subsequent dasatinib treatment most likely by subclinical CMV reactivation. This study provides a rationale for the exploitation of CMV-associated NK cell activation for treatment of leukemias.

Possible Involvement of the Rat Hypothalamo-Neurohypophysial/-Spinal Oxytocinergic Pathways in Acute Nociceptive Responses.

Oxytocin (OXT)-containing neurosecretory cells in the parvocellular divisions of the paraventricular nucleus (PVN), which project to the medulla and spinal cord, are involved in various physiological functions, such as sensory modulation and autonomic processes. In the present study, we examined OXT expression in the hypothalamo-spinal pathway, as well as the hypothalamo-neurohypophysial system, which includes the magnocellular neurosecretory cells in the PVN and the supraoptic nucleus (SON), after s.c. injection of saline or formalin into the hindpaws of transgenic rats that express the OXT and monomeric red fluorescent protein 1 (mRFP1) fusion gene. (i) The numbers of OXT-mRFP1 neurones that expressed Fos-like immunoreactivity (-IR) and OXT-mRFP1 intensity were increased significantly in the magnocellular/parvocellular PVN and SON after s.c. injection of formalin. (ii) OXT-mRFP1 neurones in the anterior parvocellular PVN, which may project to the dorsal horn of the spinal cord, were activated by s.c. injection of formalin, as indicated by a significant increases of Fos-IR and mRFP1 intensity intensity. (iii) Formalin injection caused a significant transient increase in plasma OXT. (iv) OXT, mRFP1 and corticotrophin-releasing hormone mRNAs in the PVN were significantly increased after s.c. injection of formalin. (v) An intrathecal injection of OXT-saporin induced hypersensitivity in conscious rats. Taken together, these results suggest that the hypothalamo-neurohypophysial/-spinal OXTergic pathways may be involved in acute nociceptive responses in rats.

Mixed aliphatic and aromatic composition of evaporating very small grains in NGC 7023 revealed by the 3.4/3.3 µm ratio.

CONTEXT: A chemical scenario was proposed for photon-dominated regions (PDRs) according to which UV photons from nearby stars lead to the evaporation of very small grains (VSGs) and the production of gas-phase polycyclic aromatic hydrocarbons (PAHs). AIMS: Our goal is to achieve better insight into the composition and evolution of evaporating very small grains (eVSGs) and PAHs through analyzing the infrared (IR) aliphatic and aromatic emission bands. METHODS: We combined spectro-imagery in the near- and mid-IR to study the spatial evolution of the emission bands in the prototypical PDR NGC 7023. We used near-IR spectra obtained with the IRC instrument onboard AKARI to trace the evolution of the 3.3 µm and 3.4 µm bands, which are associated with aromatic and aliphatic C-H bonds on PAHs. The spectral fitting involved an additional broad feature centered at 3.45 µm that is often referred to as the plateau. Mid-IR observations obtained with the IRS instrument onboard the Spitzer Space Telescope were used to distinguish the signatures of eVSGs and neutral and cationic PAHs. We correlated the spatial evolution of all these bands with the intensity of the UV field given in units of the Habing field G0 to explore how their carriers are processed. RESULTS: The intensity of the 3.45 µm plateau shows an excellent correlation with that of the 3.3 µm aromatic band (correlation coefficient R = 0.95) and a relatively poor correlation with the aliphatic 3.4 µm band (R=0.77). This indicates that the 3.45 µm feature is dominated by the emission from aromatic bonds. We show that the ratio of the 3.4 µm and 3.3 µm band intensity (I3.4/I3.3) decreases by a factor of 4 at the PDR interface from the more UV-shielded layers (G0 ~ 150, I3.4/I3.3 = 0.13) to the more exposed layers (G0 > 1 × 104, I3.4/I3.3 = 0.03). The intensity of the 3.3 µm band relative to the total neutral PAH intensity shows an overall increase with G0, associated with an increase of both the hardness of the UV field and the H abundance. In contrast, the intensity of the 3.4 µm band relative to the total neutral PAH intensity decreases with G0, showing that their carriers are actively destroyed by UV irradiation and are not efficiently regenerated. The transition region between the aliphatic and aromatic material is found to correspond spatially with the transition zone between neutral PAHs and eVSGs. CONCLUSIONS: We conclude that the photo-processing of eVSGs leads to the production of PAHs with attached aliphatic sidegroups that are revealed by the 3.4 µm emission band. Our analysis provides evidence for the presence of very small grains of mixed aromatic and aliphatic composition in PDRs.

Involvement of prolactin-releasing peptide in the activation of oxytocin neurones in response to food intake.

Food intake activates neurones expressing prolactin-releasing peptide (PrRP) in the medulla oblongata and oxytocin neurones in the hypothalamus. Both PrRP and oxytocin have been shown to have an anorexic action. In the present study, we investigated whether the activation of oxytocin neurones following food intake is mediated by PrRP. We first examined the expression of PrRP receptors (also known as GPR10) in rats. Immunoreactivity of PrRP receptors was observed in oxytocin neurones and in vasopressin neurones in the paraventricular and supraoptic nuclei of the hypothalamus and in the bed nucleus of the stria terminalis. Application of PrRP to isolated supraoptic nuclei facilitated the release of oxytocin and vasopressin. In mice, re-feeding increased the expression of Fos protein in oxytocin neurones of the hypothalamus and bed nucleus of the stria terminalis. The increased expression of Fos protein in oxytocin neurones following re-feeding or i.p. administration of cholecystokinin octapeptide (CCK), a peripheral satiety factor, was impaired in PrRP-deficient mice. CCK-induced oxytocin increase in plasma was also impaired in PrRP-deficient mice. Furthermore, oxytocin receptor-deficient mice showed an increased meal size, as reported in PrRP-deficient mice and in CCKA receptor-deficient mice. These findings suggest that PrRP mediates, at least in part, the activation of oxytocin neurones in response to food intake, and that the CCK-PrRP-oxytocin pathway plays an important role in the control of the termination of each meal.

Roles of oxytocin neurones in the control of stress, energy metabolism, and social behaviour.

Oxytocin neurones are activated by stressful stimuli, food intake and social attachment. Activation of oxytocin neurones in response to stressful stimuli or food intake is mediated, at least in part, by noradrenaline/prolactin-releasing peptide (PrRP) neurones in the nucleus tractus solitarius, whereas oxytocin neurones are activated after social stimuli via medial amygdala neurones. Activation of oxytocin neurones induces the release of oxytocin not only from their axon terminals, but also from their dendrites. Oxytocin acts locally where released or diffuses and acts on remote oxytocin receptors widely distributed within the brain, resulting in anxiolytic, anorexic and pro-social actions. The action sites of oxytocin appear to be multiple. Oxytocin shows anxiolytic actions, at least in part, via serotoninergic neurones in the median raphe nucleus, has anorexic actions via pro-opiomelanocortin neurones in the nucleus tractus solitarius and facilitates social recognition via the medial amygdala. Stress, obesity and social isolation are major risk factors for mortality in humans. Thus, the oxytocin-oxytocin receptor system is a therapeutic target for the promotion of human health.

Expression of exocytosis proteins in rat supraoptic nucleus neurones.

In magnocellular neurones of the supraoptic nucleus (SON), the neuropeptides vasopressin and oxytocin are synthesised and packaged into large dense-cored vesicles (LDCVs). These vesicles undergo regulated exocytosis from nerve terminals in the posterior pituitary gland and from somata/dendrites in the SON. Regulated exocytosis of LDCVs is considered to involve the soluble N-ethylmaleimide sensitive fusion protein attachment protein receptor (SNARE) complex [comprising vesicle associated membrane protein 2 (VAMP-2), syntaxin-1 and soluble N-ethylmaleimide attachment protein-25 (SNAP-25)] and regulatory proteins [such as synaptotagmin-1, munc-18 and Ca(2+) -dependent activator protein for secretion (CAPS-1)]. Using fluorescent immunocytochemistry and confocal microscopy, in both oxytocin and vasopressin neurones, we observed VAMP-2, SNAP-25 and syntaxin-1-immunoreactivity in axon terminals. The somata and dendrites contained syntaxin-1 and other regulatory exocytosis proteins, including munc-18 and CAPS-1. However, the distribution of VAMP-2 and synaptotagmin-1 in the SON was limited to putative pre-synaptic contacts because they co-localised with synaptophysin (synaptic vesicle marker) and had no co-localisation with either oxytocin or vasopressin. SNAP-25 immunoreactivity in the SON was limited to glial cell processes and was not detected in oxytocin or vasopressin somata/dendrites. The present results indicate differences in the expression and localisation of exocytosis proteins between the axon terminals and somata/dendritic compartment. The absence of VAMP-2 and SNAP-25 immunoreactivity from the somata/dendrites suggests that there might be different SNARE protein isoforms expressed in these compartments. Alternatively, exocytosis of LDCVs from somata/dendrites may use a different mechanism from that described by the SNARE complex theory.

Supernovae and the chirality of the amino acids.

A mechanism for creating amino acid enantiomerism that always selects the same large-scale chirality is identified, and subsequent chemical replication and galactic mixing that would populate the Galaxy with the predominant species is described. This involves (1) the spin of the 14N in the amino acids, or in precursor molecules from which amino acids might be formed, that couples to the chirality of the molecules; (2) the neutrinos emitted from the supernova, together with the magnetic field from the nascent neutron star or black hole formed from the supernova, which selectively destroy one orientation of the 14N and thus select the chirality associated with the other 14N orientation; (3) chemical evolution, by which the molecules replicate and evolve to more complex forms of a single chirality on a relatively short timescale; and (4) galactic mixing on a longer timescale that mixes the selected molecules throughout the Galaxy.

Long-term infusion of brain-derived neurotrophic factor reduces food intake and body weight via a corticotrophin-releasing hormone pathway in the paraventricular nucleus of the hypothalamus.

Brain-derived neurotrophic factor (BDNF) has been implicated in learning, depression and energy metabolism. However, the neuronal mechanisms underlying the effects of BDNF on energy metabolism remain unclear. The present study aimed to elucidate the neuronal pathways by which BDNF controls feeding behaviour and energy balance. Using an osmotic mini-pump, BDNF or control artificial cerebrospinal fluid was infused i.c.v. at the lateral ventricle or into the paraventricular nucleus of the hypothalamus (PVN) for 12 days. Intracerebroventricular BDNF up-regulated mRNA expression of corticotrophin-releasing hormone (CRH) and urocortin in the PVN. TrkB, the receptor for BDNF, was expressed in the PVN neurones, including those containing CRH. Both i.c.v. and intra-PVN-administered BDNF decreased food intake and body weight. These effects of BDNF on food intake and body weight were counteracted by the co-administration of alpha-helical-CRH, an antagonist for the CRH and urocortin receptors CRH-R1/R2, and partly attenuated by a selective antagonist for CRH-R2 but not CRH-R1. Intracerebroventricular BDNF also decreased the subcutaneous and visceral fat mass, adipocyte size and serum triglyceride levels, which were all attenuated by alpha-helical-CRH. Furthermore, BDNF decreased the respiratory quotient and raised rectal temperature, which were counteracted by alpha-helical-CRH. These results indicate that the CRH-urocortin-CRH-R2 pathway in the PVN and connected areas mediates the long-term effects of BDNF to depress feeding and promote lipolysis.

Participation of the prolactin-releasing peptide-containing neurones in caudal medulla in conveying haemorrhagic stress-induced signals to the paraventricular nucleus of the hypothalamus.

The prolactin-releasing peptide (PrRP) has been proposed to be a co-transmitter or modulator of noradrenaline (NA) because it colocalises with NA in the A1 (in the ventrolateral reticular formation) and A2 (in the nucleus of the solitary tract; NTS) cell groups in the caudal medulla. The baroreceptor signals, originating from the great vessels, are transmitted primarily to the NTS, and then part of the signals is conveyed to the hypothalamic neuroendocrine neurones via the ascending NA neurones. The hypotensive haemorrhagic paradigm was employed to examine whether the PrRP-containing neurones in the caudal medulla participate in conveying signals to the hypothalamic neuroendocrine neurones. Among the caudal medullary A1 or A2 neurones, the majority of the PrRP-immunoreactive (-ir) neurones became c-Fos-ir at 2 h after hypotensive haemorrhage. Hypothalamic corticotrophin-releasing hormone-ir neurones and vasopressin-ir neurones became c-Fos positive in parallel with the activation of medullary PrRP-ir neurones. After delivery of retrograde tracer fluorogold (FG) to the paraventricular nucleus of the hypothalamus (PVN), part of the PrRP/FG double-labelled neurones in the A1 and A2 became c-Fos-ir after haemorrhage, demonstrating that PrRP-ir neurones participate in conveying the haemorrhagic stress-induced signals from the medulla to the PVN. PrRP and/or NA were microinjected directly to the PVN of conscious rats, and they presented a synergistic action on arginine vasopressin release, whereas an additive action was observed for adrenocorticotrophin release. These results suggest that the PrRP-containing NA neurones in the caudal medulla may relay the haemorrhagic stress-induced medullary inputs to the hypothalamic neuroendocrine neurones.

Central endogenous vasopressin induced by central salt-loading participates in body fluid homeostasis through modulatory effects on neurones of the paraventricular nucleus in conscious rats.

Peripherally secreted arginine vasopressin (AVP) plays a role in controlling body fluid homeostasis, and central endogenous AVP acts as a neurotransmitter or neuromodulator. The limbic system, which appears to exert an inhibitory effect on the endocrine hypothalamus, is also innervated by fibres that contain AVP. We examined whether central endogenous AVP is also involved in the control of body fluid homeostasis. To explore this possibility, we examined neuronal activity in the paraventricular nucleus of the hypothalamus (PVN), periventricular parts of the PVN and limbic brain areas, as well as AVP mRNA expression in the PVN and the peripheral secretion of AVP after central salt-loading in rats that had been pretreated i.c.v. with the AVP V(1) receptor antagonist OPC-21268. Neuronal activity in the PVN evaluated in terms of Fos-like immunoreactivity (FLI), especially in the parvocellular subdivisions, was suppressed. On the other hand, FLI was enhanced in the lateral septum, the bed nucleus of the stria terminalis and the anterior hypothalamic area. Similarly, AVP mRNA expression was enhanced in the magnocellular subnucleus of the PVN, despite the lack of a significant difference in the peripheral AVP level between OPC-21268- and vehicle-pretreated groups. We recorded renal sympathetic nerve activity (RSNA) as sympathetic nerve outflow during central salt-loading. The suppression of RSNA was significantly attenuated by i.c.v. pretreatment with OPC-21268. These results suggest that the suppression of RSNA during central salt-loading might be the result of a decrease in neuronal activity in the parvocellular subdivisions of the PVN via the inhibitory action of central endogenous AVP. The parvocellular and magnocellular neurones in the PVN might show different responses to central salt-loading to maintain body fluid homeostasis as a result of the modulatory role of central endogenous AVP.

Response of arginine vasopressin-enhanced green fluorescent protein fusion gene in the hypothalamus of adjuvant-induced arthritic rats.

Arginine vasopressin (AVP) and corticotrophin-releasing hormone (CRH) in the parvocellular neurosecretory cells of the paraventricular nucleus (PVN) play a major role in activating the hypothalamic-pituitary-adrenal axis, which is the main neuroendocrine response against the many kinds of stress. We examined the effects of chronic inflammatory/nociceptive stress on the expression of the AVP-enhanced green fluorescent protein (eGFP) fusion gene in the hypothalamus, using the adjuvant arthritis (AA) model. To induce AA, the AVP-eGFP rats were intracutaneously injected heat-killed Mycobacterium butyricum (1 mg/rat) in paraffin liquid at the base of their tails. We measured AVP, oxytocin and corticosterone levels in plasma and changes in eGFP and CRH mRNA in the hypothalamus during the time course of AA development. Then, we examined eGFP fluorescence in the PVN, the supraoptic nucleus (SON), median eminence (ME) and posterior pituitary gland (PP) when AA was established. The plasma concentrations of AVP, oxytocin and corticosterone were significantly increased on days 15 and 22 in AA rats, without affecting the plasma osmolality and sodium. Although CRH mRNA levels in the PVN were significantly decreased, eGFP mRNA levels in the PVN and the SON were significantly increased on days 15 and 22 in AA rats. The eGFP fluorescence in the SON, the PVN, internal and external layers of the ME and PP was apparently increased in AA compared to control rats. These results suggest that the increases in the concentrations of ACTH and corticosterone in AA rats are induced by hypothalamic AVP, based on data from AVP-eGFP transgenic rats.

The single-prolonged stress paradigm alters both the morphology and stress response of magnocellular vasopressin neurons.

Vasopressin (AVP) plays an important role in anxiety-related and social behaviors. Single-prolonged stress (SPS) has been established as an animal acute severe stress model and has been shown to induce a lower adrenocorticotropic hormone (ACTH) response upon cortisol challenge. Here, we show results from immunoassays for AVP, ACTH, and corticosterone (CORT), and in situ hybridizations for AVP mRNA performed 7 days after SPS exposure. Immunofluorescence for AVP was also performed during the 7-day period following SPS exposure and after an additional forced swimming stress paradigm. We observed that the plasma concentrations of AVP, ACTH, and CORT were not altered by SPS; ACTH content in the pituitary and AVP mRNA expression in the supraoptic nucleus (SON) were significantly reduced by SPS. During the 7-day period following SPS, the intensity of immunoreactivity, the size of the soma, and the immunoreactive optical density of the dendrites of AVP neurons in the SON all increased. An apparent reduction in the intensity of AVP immunoreactivity was observed in the SON at 4 h after additional stress. Additional forced swimming led to a rapid increase in the dendritic AVP content only in the controls and not in the SPS-treated rats. These findings suggest that AVP is a potential biomarker for past exposure to severe stress and that alterations in AVP may affect the development of pathogenesis in stress-related disorders.

Chronic osmotic stimuli increase salusin-beta-like immunoreactivity in the rat hypothalamo-neurohypophyseal system: possible involvement of salusin-beta on [Ca2+]i increase and neurohypophyseal hormone release from the axon terminals.

Salusin-alpha and -beta were recently discovered as bioactive endogenous peptides. In the present study, we investigated the effects of chronic osmotic stimuli on salusin-beta-like immunoreactivity (LI) in the rat hypothalamo-neurohypophyseal system. We examined the effects of salusin-beta on synaptic inputs to the rat magnocellular neurosecretory cells (MNCs) of the supraoptic nucleus (SON) and neurohypophyseal hormone release from both freshly dissociated SONs and neurohypophyses in rats. Immunohistochemical studies revealed that salusin-beta-LI neurones and fibres were markedly increased in the SON and the magnocellular division of the paraventricular nucleus after chronic osmotic stimuli resulting from salt loading for 5 days and dehydration for 3 days. Salusin-beta-LI fibres and varicosities in the internal zone of the median eminence and the neurohypophysis were also increased after osmotic stimuli. Whole-cell patch-clamp recordings from rat SON slice preparations showed that salusin-beta did not cause significant changes in the excitatory and inhibitory postsynaptic currents of the MNCs. In vitro hormone release studies showed that salusin-beta evoked both arginine vasopressin (AVP) and oxytocin release from the neurohypophysis, but not the SON. In our hands, in the neurohypophysis, a significant release of AVP and oxytocin was observed only at concentrations from 100 nm and above of salusin-beta. Low concentrations below 100 nm were ineffective both on AVP and oxytocin release. We also measured intracellular calcium ([Ca(2+)](i)) increase induced by salusin-beta on freshly-isolated single nerve terminals from the neurohypophysis devoid of pars intermedia. Furthermore, this salusin-beta-induced [Ca(2+)](i) increase was blocked in the presence of high voltage activated Ca(2+)channel blockers. Our results suggest that salusin-beta may be involved in the regulation of body fluid balance by stimulating neurohypophyseal hormone release from nerve endings by an autocrine/paracrine mechanism.

Effects of the short chain sugar acid 2-buten-4-olide on the hypothalamo-pituitary-adrenal axis in normal and adjuvant-induced arthritic rats.

The effects of intraperitoneal (i.p.) administration of 2-buten-4-olide (2-B4O), an endogenous sugar acid, on the hypothalamo-adenohypophysial system were examined in Lewis rats that were normal and in adjuvant-induced arthritic (AA) rats. In comparison with vehicle-treated rats, the plasma corticosterone and c-fos mRNA levels in the paraventricular nucleus (PVN) of normal rats increased significantly after i.p. administration of 2-B4O. Dual immunostaining revealed that almost all corticotrophin-releasing factor (CRF)-immunopositive neurones in the parvocellular division of the PVN exhibited Fos-like immunoreactivity (LI) 120 min after i.p. administration of 2-B4O (100 mg/kg). In the AA rats, repeated i.p. administration of 2-B4O (100 mg/kg) after immunisation significantly suppressed the expression of clinical symptoms and significantly increased plasma concentrations of corticosterone. Further, repeated i.p. administration of 2-B4O significantly increased CRF mRNA levels in the PVN and pro-opiomelanocortin mRNA levels in the anterior pituitary; however, they did not change arginine vasopressin mRNA levels in the parvocellular division of the PVN. These results suggest that i.p. administration of 2-B4O activates the hypothalamo-pituitary-adrenal (HPA) axis via the activation of CRF neurones in the PVN, and the activation of the HPA axis by i.p. administration of 2-B4O may be associated with the inhibition of AA in rats.

Exaggerated response of arginine vasopressin-enhanced green fluorescent protein fusion gene to salt loading without disturbance of body fluid homeostasis in rats.

We examined the effects of chronic salt loading on the hypothalamic expressions of the enhanced green fluorescent protein (eGFP), arginine vasopressin (AVP) and oxytocin (OXT) genes in AVP-eGFP transgenic rats that expressed eGFP in the hypothalamic AVP-containing neurones. In these rats, salt loading for 5 days caused a marked increase of the eGFP fluorescence in the magnocellular divisions of the paraventricular nucleus (PVN), the supraoptic nucleus (SON) and the internal layer of the median eminence. Expression of the eGFP gene was increased seven- to eight-fold in the PVN and SON of salt-loaded rats in comparison with euhydrated rats. By contrast, none of these changes were observed in the suprachiasmatic nucleus. The expression of the AVP and OXT genes was increased 1.5- to two-fold in the PVN and SON of salt-loaded nontransgenic (control) and transgenic rats. There were no differences in the expression levels of the AVP and OXT genes in the PVN and SON between nontransgenic (control) and transgenic animals under normal conditions and after salt loading. In the posterior pituitary gland, the intensity of the eGFP fluorescence did not change after salt loading for 5 days, but increased after 10 days of salt loading. Upon salt loading, significant increases in the plasma AVP concentrations, plasma osmolality and plasma Na+ were observed. Furthermore, there were no significant differences in changes of water intake, food intake, urine volume, urine osmolality, urine Na+ concentrations, and the body weights in both models under normal or salt-loaded conditions. Our results show that the response of the AVP-eGFP fusion gene to chronic salt loading is exaggerated, and humoral responses such as AVP and OXT and the body fluid homeostasis are maintained in AVP-eGFP transgenic rats. The AVP-eGFP transgenic rat gives us a new opportunity to study the dynamics of the AVP system in vivo.

Prolactin-releasing peptide is a potent mediator of stress responses in the brain through the hypothalamic paraventricular nucleus.

The effects of i.c.v. administration of prolactin-releasing peptide on neurons in the paraventricular nucleus of rats and plasma corticosterone levels were examined by measuring changes in Fos-like immunoreactivity, c-fos mRNA using in situ hybridization histochemistry, and plasma corticosterone using a specific radioimmunoassay. Approximately 80% of corticotropin-releasing hormone immunoreactive cells exhibited Fos-like immunoreactivity in the parvocellular division of the paraventricular nucleus 90 min after i.c.v. administration of prolactin-releasing peptide. The greatest induction of the c-fos mRNA expression in the paraventricular nucleus was observed 30 min after administration of prolactin-releasing peptide, and occurred in a dose-related manner. Plasma corticosterone levels were also significantly increased 30 min after administration of prolactin-releasing peptide. Next, the effects of restraint stress, nociceptive stimulus and acute inflammatory stress on the expression of the prolactin-releasing peptide mRNA in the dorsomedial hypothalamic nucleus, nucleus of the solitary tract and ventrolateral medulla were examined using in situ hybridization histochemistry for prolactin-releasing peptide mRNA. Restraint stress and acute inflammatory stress upregulated the prolactin-releasing peptide mRNA expression in the nucleus of the solitary tract and ventrolateral medulla. Nociceptive stimulus upregulated the prolactin-releasing peptide mRNA expression in the ventrolateral medulla. Finally, we observed that pretreatment (i.c.v. administration) with an anti-prolactin-releasing peptide antibody significantly attenuated nociceptive stimulus-induced c-fos mRNA expression in the paraventricular nucleus. These results suggest that prolactin-releasing peptide is a potent and important mediator of the stress response in the brain through the hypothalamic paraventricular nucleus.

Cannabinoids modulate synaptic activity in the rat supraoptic nucleus.

In the present study, we investigated the effects of the cannabinoid receptor agonist CP55,940 on excitatory and inhibitory synaptic transmission in the rat supraoptic nucleus. Whole-cell patch clamp recordings were performed on supraoptic neurones in in vitro brain slice preparations. CP55,940 significantly reduced the frequency of spontaneous excitatory and inhibitory postsynaptic currents in a concentration-dependent manner. These changes were potently reversed by the CB1 receptor antagonist AM251. The results indicate that cannabinoids modulate the activity of magnocellular neurosecretory neurones by presynaptic inhibition of both excitatory and inhibitory synaptic transmission.

Neural pathways controlling central and peripheral oxytocin release during stress.

Oxytocin is released from the pituitary gland in response to a variety of stressful stimuli, including noxious stimuli, conditioned fear and exposure to novel environments. These responses are believed to be mediated, at least in part, by noradrenergic projections from the medulla oblongata, and some of these noradrenergic neurones also contain prolactin-releasing peptide (PrRP). Central administration of either PrRP or noradrenaline stimulates oxytocin secretion into the circulation. Stressful stimuli activate PrRP-containing noradrenergic neurones in the medulla oblongata, and it is thus possible that PrRP/noradrenergic projections to the hypothalamus mediate oxytocin responses to stressful stimuli. Here, the roles of brainstem PrRP/noradrenergic projections to the hypothalamus in oxytocin responses to different kinds of stressful stimuli are reviewed, with a particular emphasis on conditioned fear. Roles of dendritic oxytocin release during stress and metabolic factors affecting stress pathways are also discussed.

Intermittent footshock facilitates dendritic vasopressin release but suppresses vasopressin synthesis within the rat supraoptic nucleus.

Emotional stress inhibits vasopressin release from the pituitary but may facilitate its release from the dendrites in the hypothalamus. We examined effects of intermittently applied footshock upon the amount of vasopressin heteronuclear RNA in the hypothalamus. The footshock decreased plasma vasopressin concentration but increased its extracellular concentration within the supraoptic nucleus. The contents of the vasopressin heteronuclear RNA in the supraoptic nucleus were significantly decreased after the shock. These data suggest that intermittent footshock decreases not only vasopressin release from the axon terminals in the pituitary, but also vasopressin synthesis in the cell bodies in the hypothalamus while the stimulus facilitates vasopressin release from the dendrites in the hypothalamus. The data also suggest differential control of dendritic vasopressin release and synthesis in the hypothalamus.