Effects of peripherally administered cholecystokinin-8 and secretin on feeding/drinking and oxytocin-mRFP1 fluorescence in transgenic rats

Peripheral administration of cholecystokinin (CCK)-8 or secretin activates oxytocin (OXT)-secreting neurons in the hypothalamus. Although OXT is involved in the regulation of feeding behavior, detailed mechanism remains unclear. In the present study, we examined the central OXTergic pathways after intraperitoneally (i.p.) administration of CCK-8 and secretin using male OXT-monomeric red fluorescent protein 1 (mRFP1) transgenic rats and male Wistar rats. I.p. administration of CCK-8 (50μg/kg) and secretin (100μg/kg) decreased food intake in these rats. While i.p. administration of CCK-8 decreased water intake, i.p. administration of secretin increased water intake. Immunohistochemical study revealed that Fos-Like-Immunoreactive cells were observed abundantly in the brainstem and in the OXT neurons in the dorsal division of the parvocellular paraventricular nucleus (dpPVN). We could observe marked increase of mRFP1 fluorescence, as an indicator for OXT, in the dpPVN and mRFP1-positive granules in axon terminals of the dpPVN OXT neurons in the nucleus tractus solitarius (NTS) after i.p. administration of CCK-8 and secretin. These results provide us the evidence that, at least in part, i.p. administration of CCK-8 or secretin might be involved in the regulation of feeding/drinking via a OXTergic pathway from the dpPVN to the NTS.

Centrally administered kisspeptin suppresses feeding via nesfatin-1 and oxytocin in male rats

Kisspeptin (KP), known as a hypothalamic neuropeptide, plays a critical role in the regulation of not only reproduction but also food intake. The anorectic neuropeptides, nesfatin-1 and oxytocin (OXT), are expressed in central nervous system, particulaly in various hypothalamic nuclei, and peripheral tissue. We examined the effects of the intracerebroventricular (icv) administration of KP-10 on feeding and nesfatin-1-immunoreactive (ir) or OXT-ir neurons in the rat hypothalamus, using Fos double immunohistochemistry in male rats. Cumulative food intake was remarkably decreased 0.5-3 h after icv administration of KP-10 (6.0 μg) compared to the vehicle treated and the KP-10 (3.8 μg) treated group. The icv administration of KP-10 significantly increased the number of nesfatin-1-ir neurons expressing Fos in the supraoptic nucleus (SON), paraventricular nucleus (PVN), arcuate nucleus (ARC), dorsal raphe nucleus, locus coeruleus, and nucleus tractus solitarius. The decreased food intake induced by KP-10 was significantly attenuated by pretreatment with the icv administration of antisense RNA against nucleobindin-2. After icv administration of KP-10, the percentages of OXT-ir neurons expressing FOS were remarkably higher in the SON and PVN than for vehicle treatment. The KP-10-induced anorexia was partially abolished by pretreatment with OXT receptor antagonist (OXTR-A). The percentage of nesfatin-1-ir neurons expressing Fos-ir in the ARC was also decreased by OXTR-A pretreatment. These results indicate that central administration of KP-10 activates nesfatin-1- and OXT neurons, and may play an important role in the suppression of feeding in male rats.

Fluorescent Visualisation of Oxytocin in the Hypothalamo-neurohypophysial/-spinal Pathways After Chronic Inflammation in Oxytocin-Monomeric Red Fluorescent Protein 1 Transgenic Rats

Oxytocin (OXT) is a well-known neurohypophysial hormone that is synthesised in the paraventricular (PVN) and supraoptic nuclei (SON) of the hypothalamus. The projection of magnocellular neurosecretory cells, which synthesise OXT and arginine vasopressin in the PVN and SON, to the posterior pituitary plays an essential role in mammalian labour and lactation through its peripheral action. However, previous studies have shown that parvocellular OXTergic cells in the PVN, which project to the medulla and spinal cord, are involved in various physiological functions (e.g. sensory modulation and autonomic). In the present study, we examined OXT expression in the PVN, SON and spinal cord after chronic inflammation from adjuvant arthritis (AA). We used transgenic rats that express OXT and the monomeric red fluorescent protein 1 (mRFP1) fusion gene to visualise both the magnocellular and parvocellular OXTergic pathways. OXT-mRFP1 fluorescence intensity was significantly increased in the PVN, SON, dorsal horn of the spinal cord and posterior pituitary in AA rats. The levels of OXT-mRFP1 mRNA were significantly increased in the PVN and SON of AA rats. These results suggested that OXT was up-regulated in both hypothalamic magnocellular neurosecretory cells and parvocellular cells by chronic inflammation, and also that OXT in the PVN-spinal pathway may be involved in sensory modulation. OXT-mRFP1 transgenic rats are a very useful model for visualising the OXTergic pathways from vesicles in a single cell to terminals in in vitro preparations.

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.

Endogenous oxytocin exerts anti-nociceptive and anti-inflammatory effects in rats

Oxytocin is involved in pain transmission, although the detailed mechanism is not fully understood. Here, we generate a transgenic rat line that expresses human muscarinic acetylcholine receptors (hM3Dq) and mCherry in oxytocin neurons. We report that clozapine-N-oxide (CNO) treatment of our oxytocin-hM3Dq-mCherry rats exclusively activates oxytocin neurons within the supraoptic and paraventricular nuclei, leading to activation of neurons in the locus coeruleus (LC) and dorsal raphe nucleus (DR), and differential gene expression in GABA-ergic neurons in the L5 spinal dorsal horn. Hyperalgesia, which is robustly exacerbated in experimental pain models, is significantly attenuated after CNO injection. The analgesic effects of CNO are ablated by co-treatment with oxytocin receptor antagonist. Endogenous oxytocin also exerts anti-inflammatory effects via activation of the hypothalamus-pituitary-adrenal axis. Moreover, inhibition of mast cell degranulation is found to be involved in the response. Taken together, our results suggest that oxytocin may exert anti-nociceptive and anti-inflammatory effects via both neuronal and humoral pathways.

Neuropathic Pain Up-Regulates Hypothalamo-Neurohypophysial and Hypothalamo-Spinal Oxytocinergic Pathways in Oxytocin-Monomeric Red Fluorescent Protein 1 Transgenic Rat

Despite the high incidence of neuropathic pain, its mechanism remains unclear. Oxytocin (OXT) is an established endogenous polypeptide produced in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus. OXT, which is synthesized by OXT neurons in the SON and the magnocellular part of the PVN (mPVN), is delivered into the posterior pituitary (PP), then released into the systemic blood circulation. Meanwhile, OXT-containing neurosecretory cells in the parvocellular part of the PVN (pPVN) are directly projected to the spinal cord and are associated with sensory modulation. In this study, the OXT system in the hypothalamo-neurohypophysial and hypothalamo-spinal pathway was surveyed using a rat neuropathic pain model induced by partial sciatic nerve ligation (PSL). In the present study, we used transgenic rats expressing an OXT-monomeric red fluorescent protein 1 (mRFP1) fusion gene. In a neuropathic pain model, mechanical allodynia was observed, and glial cell activation was also confirmed via immunohistochemistry. In this neuropathic pain model, a significant increase in the OXT-mRFP1 expression was observed in the PP, the SON, mPVN, and pPVN. Furthermore, OXT-mRFP1 granules with positive fluorescent reaction were remarkably increased in laminae I and II of the ipsilateral dorsal horn. Although the plasma concentrations of OXT did not significantly change, a significant increase of the mRNA levels of OXT and mRFP1 in the SON, mPVN, and pPVN were observed. These results suggest that neuropathic pain induced by PSL upregulates hypothalamic OXT synthesis and transportation to the OXTergic axon terminals in the PP and spinal cord.

Activation of Nesfatin-1-Containing Neurones in the Hypothalamus and Brainstem by Peripheral Administration of Anorectic Hormones and Suppression of Feeding via Central Nesfatin-1 in Rats

Peripheral anorectic hormones, such as glucagon-like peptide (GLP)-1, cholecystokinin (CCK)-8 and leptin, suppress food intake. The newly-identified anorectic neuropeptide, nesfatin-1, is synthesised in both peripheral tissues and the central nervous system, particularly by various nuclei in the hypothalamus and brainstem. In the present study, we examined the effects of i.p. administration of GLP-1 and CCK-8 and co-administrations of GLP-1 and leptin at subthreshold doses as confirmed by measurement of food intake, on nesfatin-1-immunoreactive (-IR) neurones in the hypothalamus and brainstem of rats by Fos immunohistochemistry. Intraperitoneal administration of GLP-1 (100 μg/kg) caused significant increases in the number of nesfatin-1-IR neurones expressing Fos-immunoreactivity in the supraoptic nucleus (SON), the area postrema (AP) and the nucleus tractus solitarii (NTS) but not in the paraventricular nucleus (PVN), the arcuate nucleus (ARC) or the lateral hypothalamic area (LHA). On the other hand, i.p. administration of CCK-8 (50 μg/kg) resulted in marked increases in the number of nesfatin-1-IR neurones expressing Fos-immunoreactivity in the SON, PVN, AP and NTS but not in the ARC or LHA. No differences in the percentage of nesfatin-1-IR neurones expressing Fos-immunoreactivity in the nuclei of the hypothalamus and brainstem were observed between rats treated with saline, GLP-1 (33 μg/kg) or leptin. However, co-administration of GLP-1 (33 μg/kg) and leptin resulted in significant increases in the number of nesfatin-1-IR neurones expressing Fos-immunoreactivity in the AP and the NTS. Furthermore, decreased food intake induced by GLP-1, CCK-8 and leptin was attenuated significantly by pretreatment with i.c.v. administration of antisense nesfatin-1. These results indicate that nesfatin-1-expressing neurones in the brainstem may play an important role in sensing peripheral levels of GLP-1 and leptin in addition to CCK-8, and also suppress food intake 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 2 h 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), 90 min 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.

Transient receptor potential vanilloid 1 and 4 double knockout leads to increased bone mass in mice

Calcium balance is important in bone homeostasis. The transient receptor potential vanilloid (TRPV) channel is a nonselective cation channel permeable to calcium and is activated by various physiological and pharmacological stimuli. TRPV1 and TRPV4, in particular, have important roles in intracellular Ca²⁺ signaling and extracellular calcium homeostasis in bone cells. TRPV1 and TRPV4 separately mediate osteoclast and osteoblast differentiation, and deficiency in any of these channels leads to increased bone mass. However, it remains unknown whether bone mass increases in the absence of both TRPV1 and TRPV4. In this study, we used TRPV1 and TRPV4 double knockout (DKO) mice to evaluate their bone mass in vivo, and osteoclast and osteoblast differentiation in vitro. Our results showed that DKO mice and wild type (WT) mice had no significant difference in body weight and femur length. However, the results of dual-energy X-ray absorption, microcomputed tomography, and bone histomorphometry clearly showed that DKO mice had higher bone mass than WT mice. Furthermore, DKO mice had less multinucleated osteoclasts and had lower bone resorption. In addition, the results of cell culture using flushed bone marrow from mouse femurs and tibias showed that osteoclast differentiation was suppressed, whereas osteoblast differentiation was promoted in DKO mice. In conclusion, our results suggest that the increase in bone mass in DKO mice was induced not only by the suppression of osteoclast differentiation and activity but also by the augmentation of osteoblast differentiation and activity. Our findings reveal that both the single deficiency of TRPVs and the concurrent deficiency of TRPVs result in an increase in bone mass. Furthermore, our data showed that DKO mice and single KO mice had varying approaches to osteoclast and osteoblast differentiation in vitro, and therefore, it is important to conduct further studies on TRPVs regarding the increase in bone mass to explore not only individual but also a combination of TRPVs.

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Knockout of either TRPV1 or TRPV4 results in increased bone mass in mice.

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This study evaluates the effects of TRPV1 and TRPV4 double knockout (DKO) in mice.

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Concurrent TRPV1 and TRPV4 deficiency increases mouse bone mass.

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TRPV1 and TRPV4 DKO suppresses osteoclast differentiation and activity.

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TRPV1 and TRPV4 DKO enhances osteoblast differentiation and activity.

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 PYY_3-36, 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 PYY_3-36. 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.

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.

Effects of acute kidney dysfunction on hypothalamic arginine vasopressin synthesis in transgenic rats

Acute loss of kidney function is a critical internal stressor. Arginine vasopressin (AVP) present in the parvocellular division of the paraventricular nucleus (PVN) plays a key role in the regulation of stress responses. However, hypothalamic AVP dynamics during acute kidney dysfunction remain unclear. In this study, we investigated the effects of bilateral nephrectomy on AVP, using a transgenic rat line that expressed the AVP-enhanced green fluorescent protein (eGFP). The eGFP fluorescent intensities in the PVN were dramatically increased after bilateral nephrectomy. The mRNA levels of eGFP, AVP, and corticotrophin-releasing hormone in the PVN were dramatically increased after bilateral nephrectomy. Bilateral nephrectomy also increased the levels of Fos-like immunoreactive cells in brainstem neurons. These results indicate that bilateral nephrectomy upregulates the AVP-eGFP synthesis. Further studies are needed to identify the neural and/or humoral factors that activate AVP synthesis and regulate neuronal circuits during acute kidney dysfunction.

Acute Mono-Arthritis Activates the Neurohypophysial System and Hypothalamo-Pituitary Adrenal Axis in Rats

Various types of acute/chronic nociceptive stimuli cause neuroendocrine responses such as activation of the hypothalamo-neurohypophysial [oxytocin (OXT) and arginine vasopressin (AVP)] system and hypothalamo-pituitary adrenal (HPA) axis. Chronic multiple-arthritis activates the OXT/AVP system, but the effects of acute mono-arthritis on the OXT/AVP system in the same animals has not been simultaneously evaluated. Further, AVP, not corticotropin-releasing hormone (CRH), predominantly activates the HPA axis in chronic multiple-arthritis, but the participation of AVP in HPA axis activation in acute mono-arthritis remains unknown. Therefore, we aimed to simultaneously evaluate the effects of acute mono-arthritis on the activity of the OXT/AVP system and the HPA axis. In the present study, we used an acute mono-arthritic model induced by intra-articular injection of carrageenan in a single knee joint of adult male Wistar rats. Acute mono-arthritis was confirmed by a significant increase in knee diameter in the carrageenan-injected knee and a significant decrease in the mechanical nociceptive threshold in the ipsilateral hind paw. Immunohistochemical analysis revealed that the number of Fos-immunoreactive (ir) cells in the ipsilateral lamina I-II of the dorsal horn was significantly increased, and the percentage of OXT-ir and AVP-ir neurons expressing Fos-ir in both sides of the supraoptic (SON) and paraventricular nuclei (PVN) was increased in acute mono-arthritic rats. in situ hybridization histochemistry revealed that levels of OXT mRNA and AVP hnRNA in the SON and PVN, CRH mRNA in the PVN, and proopiomelanocortin mRNA in the anterior pituitary were also significantly increased in acute mono-arthritic rats. Further, plasma OXT, AVP, and corticosterone levels were significantly increased in acute mono-arthritic rats. These results suggest that acute mono-arthritis activates ipsilateral nociceptive afferent pathways at the spinal level and causes simultaneous and integrative activation of the OXT/AVP system. In addition, the HPA axis is activated by both AVP and CRH in acute mono-arthritis with a distinct pattern compared to that in chronic multiple-arthritis.

The neurohypophysial oxytocin and arginine vasopressin system is activated in a knee osteoarthritis rat model

Osteoarthritis (OA) causes chronic joint pain and significantly impacts daily activities. Hence, developing novel treatment options for OA has become an increasingly important area of research. Recently, studies have reported that exogenous, as well as endogenous, hypothalamic-neurohypophysial hormones, oxytocin (OXT) and arginine-vasopressin (AVP), significantly contribute to nociception modulation. Moreover, the parvocellular OXT neurone (parvOXT) extends its projection to the superficial spinal dorsal horn, where it controls the transmission of nociceptive signals. Meanwhile, AVP produced in the magnocellular AVP neurone (magnAVP) is released into the systemic circulation where it contributes to pain management at peripheral sites. The parvocellular AVP neurone (parvAVP), as well as corticotrophin-releasing hormone (CRH), suppresses inflammation via activation of the hypothalamic-pituitary adrenal (HPA) axis. Previously, we confirmed that the OXT/AVP system is activated in rat models of pain. However, the roles of endogenous hypothalamic-neurohypophysial hormones in OA have not yet been characterised. In the present study, we investigated whether the OXT/AVP system is activated in a knee OA rat model. Our results show that putative parvOXT is activated and the amount of OXT-monomeric red fluorescent protein 1 positive granules in the ipsilateral superficial spinal dorsal horn increases in the knee OA rat. Furthermore, both magnAVP and parvAVP are activated, concurrent with HPA axis activation, predominantly modulated by AVP, and not CRH. The OXT/AVP system in OA rats was similar to that in systemic inflammation models, including adjuvant arthritis; however, magnocellular OXT neurones (magnOXT) were not activated in OA. Hence, localised chronic pain conditions, such as knee OA, activate the OXT/AVP system without impacting magnOXT.

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.

Upregulation of hypothalamic arginine vasopressin by peripherally administered furosemide in transgenic rats expressing arginine vasopressin-enhanced green fluorescent protein

Furosemide, which is used worldwide as a diuretic agent, inhibits sodium reabsorption in the Henle's loop, resulting in diuresis and natriuresis. Arginine vasopressin (AVP) is synthesized in the supraoptic nucleus (SON), paraventricular nucleus (PVN), and suprachiasmatic nucleus (SCN) of the hypothalamus. The synthesis AVP in the magnocellular neurons of SON and PVN physiologically regulated by plasma osmolality and blood volume and contributed water homeostasis by increasing water reabsorption in the collecting duct. Central AVP dynamics after peripheral administration of furosemide remain unclear. Here, we studied the effects of intraperitoneal (i.p.) administration of furosemide (20 mg/kg) on hypothalamic AVP by using transgenic rats expressing AVP-enhanced green fluorescent protein (eGFP) under the AVP promoter. The i.p. administration of furosemide did not affect plasma osmolality in the present study; however, eGFP in the SON and magnocellular divisions of the PVN (mPVN) were significantly increased after furosemide administration compared to the control. Immunohistochemical analysis revealed Fos-like immunoreactivity (IR) in eGFP-positive neurons in the SON and mPVN 90 min after i.p. administration of furosemide, and AVP heteronuclear (hn) RNA and eGFP mRNA levels were significantly increased. These furosemide-induced changes were not observed in the suprachiasmatic AVP neurons. Furthermore, furosemide induced a remarkable increase in Fos-IR in the organum vasculosum laminae terminals (OVLT), median preoptic nucleus (MnPO), subfornical organ (SFO), locus coeruleus (LC), nucleus of the solitary tract (NTS), and rostral ventrolateral medulla (RVLM) after i.p. administration of furosemide. In conclusion, we were able to visualize and quantitatively evaluate AVP-eGFP synthesis and neuronal activations after peripheral administration of furosemide, using the AVP-eGFP transgenic rats. The results of this study may provide new insights into the elucidation of physiological mechanisms underlying body fluid homeostasis induced by furosemide. This article is protected by copyright. All rights reserved.

Expression of hypothalamic feeding-related peptide genes and neuroendocrine responses in an experimental allergic encephalomyelitis rat model

Experimental allergic encephalomyelitis (EAE) is considered to be a useful animal model of human multiple sclerosis (MS). However, among the various symptoms of MS, the mechanisms contributing to inflammatory anorexia remain unclear. In the present study, we used an EAE rat model to examine changes in expression levels of hypothalamic feeding-related peptide genes and neuroendocrine responses such as the hypothalamo-neurohypophysial system and the hypothalamo-pituitary-adrenal (HPA) axis. The weight gain and cumulative food intake in EAE rats in the early days after immunization was significantly lower than that of the control group. The expression of orexigenic peptide genes Npy and Agrp were significantly increased, whereas the levels of anorectic peptide genes (Pomc and Cart) were significantly decreased in the hypothalamus of EAE rats. There was also a significant increase in the mRNA and plasma oxytocin (OXT) but not of arginine vasopressin (AVP) in the supraoptic and paraventricular nuclei (PVN) of EAE rats at days 12 and 18 after immunization. The expression of corticotropin-releasing hormone (Crh) and Avp was downregulated and upregulated, respectively, in the parvocellular division of the PVN at day 12 after immunization. The expression level of Pomc in the anterior pituitary significantly increased, accompanied by increased plasma corticosterone levels, at days 6, 12, and 18 after immunization. These results suggest that inflammatory anorexia in rat EAE may be caused by activation of the OXT-ergic pathway and HPA axis via changes in the expression of hypothalamic feeding-related peptides, including Avp but not Crh.

Analysis of the proportion and neuronal activity of excitatory and inhibitory neurons in the rat dorsal spinal cord after peripheral nerve injury

The dorsal spinal cord contains projection neurons that transmit somatosensory information to the brain and interneurons which then modulate neuronal activity of these projection neurons and/or other interneurons. Interneurons can be subdivided into two groups: excitatory and inhibitory neurons. While inhibitory interneurons are thought to play a crucial role in analgesia, it is unclear whether they are involved in neuropathic pain. In the present study, we aimed to assess the proportion and neuronal activity of excitatory/inhibitory neurons in the dorsal spinal cord using a neuropathic pain model in rats. Following partial sciatic nerve ligation (PSNL), rats showed significant mechanical hyperalgesia, and subsequent immunohistochemical studies were conducted in laminae I-III of the dorsal spinal cord. We found that the number of FosB-immunoreactive cells was significantly higher; there was no change in the percentage of Pax2 positive/negative neurons in NeuN positive neurons; Pax2 negative neurons, but not Pax2 positive neurons, were predominantly activated in PSNL rats; and the immunofluorescence intensity of the calcium channel α2δ1 subunit was significantly higher. These results indicate that while peripheral nerve injury might not affect the proportion of excitatory and inhibitory neurons, it predominantly activates excitatory neurons in laminae I-III of the rat dorsal spinal cord.

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

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.

Peripherally administered cisplatin activates a parvocellular neuronal subtype expressing arginine vasopressin and enhanced green fluorescent protein in the paraventricular nucleus of a transgenic rat

Cisplatin is one of the most potent anti-cancer drugs, though several side effects can induce stress responses such as activation of the hypothalamic-pituitary adrenal (HPA) axis. Arginine vasopressin (AVP) and corticotrophin-releasing hormone (CRH) expressed in the parvocellular division of the paraventricular nucleus (pPVN) play an important role in the stress-induced activation of the HPA axis. We aimed to evaluate whether intraperitoneal (i.p.) administration of cisplatin could activate parvocellular neurons in the pPVN, using a transgenic rat model that expresses the fusion gene of AVP and enhanced green fluorescent protein (eGFP). Along with the induction of FosB, a marker of neuronal activation, i.p. administration of cisplatin significantly increased eGFP fluorescent intensities in the pPVN. In situ hybridization histochemistry revealed that AVP-eGFP and CRH mRNAs in the pPVN were increased significantly in cisplatin-treated rats. These results suggest that cisplatin administration increases neuronal activation and upregulates AVP and CRH expression in the pPVN.

DAIR in treating chronic PJI after total knee arthroplasty using continuous local antibiotic perfusion therapy: a case series study

BACKGROUND

Antimicrobial agents are administered via intramedullary antibiotic perfusion (iMAP)/intrasoft tissue antibiotic perfusion (iSAP) to infected lesions to control osteoarticular and soft tissue infections. Continuous local antibiotic perfusion (CLAP) has been reported to be useful. This study aimed to investigate the outcomes of DAIR combined with CLAP for chronic PJI after total knee arthroplasty performed at our hospital.

SUBJECTS AND METHODS

Six patients (male; one case, female; five cases, mean age 79.5 years (70-94)) underwent CLAP for chronic PJI after TKA at our hospital between July 2020 and June 2022. They were followable for at least one year after surgery. Seven months (17-219), with a mean follow-up of 24.3 months (12-36). In addition to direct debridement and insert exchange, systemic antimicrobial treatment, and CLAP with gentamicin were performed using NPWT. We investigated the organisms causing the inflammation, the duration of iMAP/iSAP implantation, the maximum daily dose of GM, the maximum GM blood concentration, and the presence or absence of GM-induced adverse events.

RESULT

Two of six patients had a recurrence of infection at five weeks and five months after initial CLAP and required repeat CLAP treatment, but all patients could preserve their components. The organisms responsible for the flare-ups were MSSA in three cases: ESBL-producing E. coli, mixed MSSA and streptococcal infection, Klebsiella pneumonia in one case each, and unknown pathogens in one case. CLAP therapy for all patients was administered eight times in 6 cases: iMAP, mean: 10.0 days (5-16); iSAP, mean: 19.3 days (15-28); GM dose, mean: 162.5 mg/day (80-240); and GM blood concentration, mean: 1.4 µg/mL (0.2-5.0). Adverse events included one case of reversible acute kidney injury during CLAP in a patient with recurrent infection. DAIR with CLAP for chronic post-TKA infection can be a useful treatment option to preserve components and allow the infection to subside, provided the implant is not markedly loosened.

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

The article Inhibition of ghrelin-induced feeding in rats by pretreatment with a novel dual orexin receptor antagonist, written by Mariko So, Hirofumi Hashimoto.