Hiromichi Ueno

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.

Inhibition of ghrelin-induced feeding in rats by pretreatment with a novel dual orexin receptor antagonist

Orexin-A and -B, and ghrelin are potent orexigenic peptides. The effects of ACT462206, a novel dual orexin receptor antagonist (DORA), on ghrelin-induced feeding were examined in adult male Wistar rats. Hyperphagia induced by the intracerebroventricular (icv) administration of ghrelin was significantly suppressed for at least 2xa0h by pretreatment with icv administration of DORA. A marked increase was observed in the number of neurons showing Fos immunoreactivity in the paraventricular nucleus, arcuate nucleus and lateral hypothalamic area (LHA), 90xa0min after icv administration of ghrelin. Pretreatment with DORA significantly decreased the number of Fos-immunoreactive (IR) neurons; however, Fos immunoreactivity remained significantly increased. Double-immunostaining for Fos and orexin-A showed that many orexin-A-IR neurons in the LHA coexisted with Fos immunoreactivity after icv administration of ghrelin, but their number was reduced significantly by DORA pretreatment. These results suggest that centrally administered ghrelin may activate the orexinergic and non-orexinergic pathways responsible for the regulation of feeding.

Involvement of central nesfatin-1 neurons on oxytocin-induced feeding suppression in rats

Peripheral anorectic hormones, such as peptide YY (PYY) and oxytocin (OXT), suppress food intake. A newly identified anorectic neuropeptide, nesfatin-1, is synthesized in both peripheral tissue and the central nervous system, particularly by various nuclei in the hypothalamus and brainstem. Here, we examined the effects of intraperitoneal (ip) administration of PYY3-36, OXT, and OXT analog, on nesfatin-1-immunoreactive (ir) neurons in the rat hypothalamus and brainstem, using Fos double fluorescence-immunohistochemistry. The ip administration of OXT and OXT analog significantly increased the number of nesfatin-1-ir neurons expressing Fos-ir in the paraventricular nucleus, the arcuate nucleus, and the nucleus tractus solitarius, but not in the supraoptic nucleus, the lateral hypothalamic area, and the area postrema. No differences in the percentage of nesfatin-1-ir neurons expressing Fos in the nuclei of the hypothalamus and brainstem were observed, between rats treated with vehicle or those treated with PYY3-36. The decreased food intake, induced by OXT and OXT analog, was attenuated significantly by pretreatment with intracerebroventricular administration of antisense nesfatin-1. These results suggested that nesfatin-1-expressing neurons in the hypothalamus and brainstem may play a role in sensing the peripheral level of OXT and its suppression of feeding in rats.

Comparison of the induction of c-fos-eGFP and Fos protein in the rat spinal cord and hypothalamus resulting from subcutaneous capsaicin or formalin injection

We evaluated whether a c-fos-enhanced green fluorescent protein (eGFP) transgenic rat line, which expresses the c-fos and eGFP fusion gene, can be useful for the study of nociceptive pathways and processing. Capsaicin solution (15%) or formalin (5%) was subcutaneously injected bilaterally into the hind paws (100μL per each paw) of adult male c-fos-eGFP transgenic or wild-type rats. Control rats were injected with ethanol or physiological saline respectively. Transgenic and wild-type rats were perfused at 1.5, 3 and 6h post injection, with some transgenic rats being perfused 24h post injection. A comparison of eGFP in transgenic rats and Fos-like immunoreactivity (LI) in wild-type rats was made in the dorsal spinal cord, paraventricular nucleus (PVN) and supraoptic nucleus (SON). Oxytocin-LI (OXT-LI) was carried out to examine the activation of OXT neurons in the PVN and SON. Following capsaicin or formalin treatment, eGFP was maximally expressed at 6h in the spinal cord and 3h in the PVN and SON, whereas, Fos-LI was maximally expressed at 1.5h in all the regions we analyzed. Induction of eGFP in the OXT neurons was observed after capsaicin or formalin treatment, while Fos-LI in the OXT neurons was observed only after formalin treatment. These results demonstrate that the peak induction of c-fos-eGFP following exposure to acute nociceptive stimuli was delayed by around 1.5-4.5h, but more sensitive than endogenous Fos, suggesting that the c-fos-eGFP rat line can be useful for the study of nociceptive pathways and processing.

Effects of central administration of oxytocin-saporin cytotoxin on chronic inflammation and feeding/drinking behaviors in adjuvant arthritic rats

An increase in the arthritis index as a marker of chronic inflammation and suppression of food intake are observed in adjuvant arthritic (AA) rats. Our previous study demonstrated that central oxytocin (OXT)-ergic pathways were activated potently in AA rats. In the present study, OXT-saporin (SAP) cytotoxin, which chemically disrupts OXT signaling was administered centrally to determine whether central OXT may be involved in the developments of chronic inflammation and alteration of feeding/drinking behavior in AA rats. The arthritis index was significantly enhanced in AA rats pretreated with OXT-SAP administered intrathecally (i.t.) but not intracerebroventricularly (i.c.v.). Suppression of food intake was significantly attenuated transiently in AA rats pretreated with OXT-SAP administered i.c.v. but not i.t. Suppression of drinking behavior was not affected by i.t. or i.c.v. administration of OXT-SAP in AA rats. In addition, intraperitoneal administration of an OXT receptor antagonist did not change the arthritis index or feeding/drinking behavior in AA rats. These results suggest that central OXT-ergic pathways may be involved in anti-inflammation at the spinal level and suppression of feeding behavior at the forebrain-brainstem level in AA rats.

Activation of central nesfatin-1/NucB2 after intraperitoneally administered cisplatin in rats

Cisplatin, known as an anticancer drug, has been widely used; however, diverse disadvantageous side effects, including appetite loss, afflict patients. Nesfatin-1/NucB2, discovered as an anorexic neuropeptide, is broadly expressed in the central nervous system (CNS) and peripheral organ. In the present study, we examined the effects of intraperitoneally (i.p.) administered cisplatin on central nesfatin-1/NucB2. Saline, as control, or cisplatin (6xa0mg/kg dissolved in saline) was i.p. administered in adult male Wistar rats (180-220xa0g). Cumulative food intake was remarkably suppressed for at least 24xa0h and body weight was significantly smaller at 24xa0h after i.p. administration of cisplatin compared to control group. At 90xa0min after i.p. administration, they were perfused, followed by carrying out double-immunohistochemistry for Fos and nesfatin-1/NucB2. The percentage of nesfatin-1/NucB2 immunoreactive neurons expressing Fos was marked increased in the hypothalamus and brainstem after i.p. administration of cisplatin. Intracerebroventricularlly administered nesfatin-1/NucB2-antisense resulted in a significant attenuation of decreased food intake for 2xa0h after i.p. administration of cisplatin compared to nesfatin-1/NucB2-missense treated group. These results suggest that i.p. administration of cisplatin activated, at least in part, nesfatin-1/NucB2 neuron in the CNS and may exert anorexigenic effects in rats.

Possible involvement of central oxytocin in cisplatin-induced anorexia in rats

During cancer chemotherapy, drugs such as 5-HT3 receptor antagonists have typically been used to control vomiting and anorexia. We examined the effects of oxytocin (OXT), which has been linked to appetite, on cisplatin-induced anorexia in rats. Fos-like immunoreactivity (Fos-LI) expressed in the supraoptic nucleus (SON), the paraventricular nucleus (PVN), the area postrema and the nucleus of the solitary tract (NTS) after intraperitoneal (ip) administration of cisplatin. We also examined the fluorescence intensity of OXT-mRFP1 after ip administration of cisplatin in OXT-mRFP1 transgenic rats. The mRFP1 fluorescence intensity was significantly increased in the SON, the PVN, and the NTS after administration of cisplatin. The cisplatin-induced anorexia was abolished by OXT receptor antagonist (OXTR-A) pretreatment. In the OXT-LI cells, cisplatin-induced Fos expression in the SON and the PVN was also suppressed by OXTR-A pretreatment. These results suggested that central OXT may be involved in cisplatin-induced anorexia in rats.

Activation of endogenous arginine vasopressin neurons inhibit food intake: by using a novel transgenic rat line with DREADDs system

Various studies contributed to discover novel mechanisms of central arginine vasopressin (AVP) system responsible for the behaviour albeit endogenous vasopressin activation. We established a novel transgenic rat line which expresses both human muscarinic acetylcholine receptors (hM3Dq), of which ligand is clozapine-N-oxide (CNO), and mCherry fluorescence specifically in AVP neurons. The mCherry neurons that indicate the expression of the hM3Dq gene were observed in the suprachiasmatic (SCN), supraoptic (SON), and paraventricular nuclei (PVN). hM3Dq-mCherry fluorescence was localized mainly in the membrane of the neurons. The mCherry neurons were co-localized with AVP-like immunoreactive (LI) neurons, but not with oxytocin-LI neurons. The induction of Fos, which is the indicator for neuronal activity, was observed in approximately 90% of the AVP-LI neurons in the SON and PVN 90u2009min after intraperitoneal (i.p.) administration of CNO. Plasma AVP was significantly increased and food intake, water intake, and urine volume were significantly attenuated after i.p. administration of CNO. Although the detailed mechanism has unveiled, we demonstrated, for the first time, that activation of endogenous AVP neurons decreased food intake. This novel transgenic rat line may provide a revolutionary insight into the neuronal mechanism regarding central AVP system responsible for various kind of behaviours.

Increased oxytocin-monomeric red fluorescent protein 1 fluorescent intensity with urocortin-like immunoreactivity in the hypothalamo-neurohypophysial system of aged transgenic rats

To visualize oxytocin in the hypothalamo-neurohypophysial system, we generated a transgenic rat that expresses the oxytocin-monomeric red fluorescent protein 1 (mRFP1) fusion gene. In the present study, we examined the age-related changes of oxytocin-mRFP1 fluorescent intensity in the posterior pituitary (PP), the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) of transgenic rats. The mRFP1 fluorescent intensities were significantly increased in the PP, the SON and the PVN of 12-, 18- and 24-month-old transgenic rats in comparison with 3-month-old transgenic rats. Immunohistochemical staining for urocortin, which belongs to the family of corticotropin-releasing factor family, revealed that the numbers of urocortin-like immunoreactive (LI) cells in the SON and the PVN were significantly increased in 12-, 18- and 24-month-old transgenic rats in comparison with 3-month-old transgenic rats. Almost all of urocortin-LI cells co-exist mRFP1-expressing cells in the SON and the PVN of aged transgenic rats. These results suggest that oxytocin content of the hypothalamo-neurohypophysial system may be modulated by age-related regulation. The physiological role of the co-existence of oxytocin and urocortin in the SON and PVN of aged rats remains unclear.

Effects of hypergravity on the gene expression of the hypothalamic feeding-related neuropeptides in mice via vestibular inputs

HighlightsInvolvement of hypergravity and vestibular system on feeding regulation was examined.Vestibular dysfunction was generated by vestibular lesion (VL).Hypothalamic gene expression was examined by in situ hybridization histochemistry.CRH and POMC were increased significantly in Sham but not in VL in 2 g environment.CRH and POMC may be responsible for feeding regulation in different gravity. ABSTRACT The effects of hypergravity on the gene expression of the hypothalamic feeding‐related neuropeptides in sham‐operated (Sham) and vestibular‐lesioned (VL) mice were examined by in situ hybridization histochemistry. Corticotrophin‐releasing hormone (CRH) in the paraventricular nucleus was increased significantly in Sham but not in VL mice after 3 days of exposure to a 2 g environment compared with a 1 g environment. Significant decreases in pro‐opiomelanocortin (POMC) and cocaine‐ and amphetamine‐regulated transcript and significant increases in neuropeptide Y, agouti‐related protein in the arcuate nucleus and orexin in the lateral hypothalamic area were observed in both Sham and VL mice. After 2 weeks of exposure, CRH and POMC were increased significantly in Sham but not in VL mice. After 8 weeks of exposure, the hypothalamic feeding‐related neuropeptides were comparable between Sham and VL mice. These results suggest that the hypothalamic feeding‐related neuropeptides may be affected during the exposed duration of hypergravity via vestibular inputs.