Hirohumi Suzuki

Neuropeptide Y-immunoreactive neuronal system and colocalization with FMRFamide in the optic lobe and peduncle complex of the octopus ( Octopus vulgaris )

Abstract. The distribution of neuropeptide Y (NPY)-like immunoreactivity and its colocalization with FMRFamide were investigated in the optic lobe and peduncle complex of the octopus (Octopus vulgaris) by using immunohistochemical techniques. In the optic lobe cortex, NPY-immunoreactive (NPY-IR) fibers were observed in the plexiform layer, although no NPY-IR somata were observed in the outer or inner granular cell layers. In the optic lobe medulla, NPY-IR somata were seen in the cell islands, and abundant NPY-IR varicose fibers were observed in the neuropil. Most of the NPY-IR structures in the medulla showed FMRFamide-like immunoreactivity. In the peduncle lobe, abundant NPY-IR and FMRFamide-IR (NPY/FMRF-IR) varicose fibers were seen in the basal zone neuropil of the peduncle lobe. In the olfactory lobe, NPY/FMRF-IR varicose fibers were also abundant in the neuropil of the three lobules. NPY/FMRF-IR somata, with processes running to various neuropils, were scattered in the median and posterior lobules. In the optic gland, many NPY/FMRF-IR varicose fibers formed a honeycomb pattern. These observations suggest that NPY/FMRF-IR neurons in the optic lobes participate in the modulation of visual information and that those in the optic gland are involved in the regulation of endocrine function.

Orexin and neuropeptide Y: tissue specific expression and immunoreactivity in the hypothalamus and preoptic area of the cichlid fish Cichlasoma dimerus.

Neuropeptide Y (NPY) and orexin are neuropeptides involved in the regulation of feeding in vertebrates. In this study we determined the NPY and orexin mRNA tissue expression and their immunoreactivity distribution in both preoptic area and hypothalamus, regions involved in the regulation of feeding behavior. Both peptides presented a wide expression in all tissues examined. The NPY-immunoreactive (ir) cells were localized in the ventral nucleus posterioris periventricularis (NPPv) and numerous ir-NPY fibers were found in the nucleus lateralis tuberis (NLT), the nucleus recess lateralis (NRL) and the neurohypophysis. Ir-orexin cells were observed in the NPPv, dorsal NLT, ventral NLT, lateral NLT (NLTl) and the lateral NRL. Ir-orexin fibers were widespread distributed along all the hypothalamus, especially in the NLTl. Additionally, we observed the presence of ir-orexin immunostaining in adenohypophyseal cells, especially in somatotroph cells and the presence of a few ir-orexin-A fibers in the neurohypophysis. In conclusion, both peptides have an ubiquitous mRNA tissue expression and are similarly distributed in the hypothalamus and preoptic area of Cichlasoma dimerus. The presence of ir-orexin in adenohypohyseal cells and the presence of ir-orexin and NPY fibers in the neurohypophysis suggest that both peptides may play an important neuroendocrine role in anterior pituitary.

Orexin-A immunoreactive cells and fibers in the central nervous system of the axolotl brain and their association with tyrosine hydroxylase and serotonin immunoreactive somata.

Orexin-A-like immunoreactivity in the axolotl brain was investigated by immunohistochemistry. Immunoreactive somata formed a single group in the hypothalamus, but were distributed beyond several nuclei, namely, the ventral aspect of the nucleus preopticus posterior, dorsal aspect of the nucleus suprachiasmaticus and anterior aspect of the pars ventralis hypothalami. Immunoreactive fibers were distributed throughout the brain from the olfactory bulb to the spinal cord except the cerebellum. The densest immunoreactive fibers were seen in the medial forebrain bundle and caudal lateral forebrain bundle. The largest number of immunoreactive puncta were seen in the mesencephalic tectum in addition to the hypothalamus. Immunoelectron microscopic analysis revealed the presence of synaptoid connections of immunoreactive fibers on neuronal somata in the tectum. The function of the mesencephalic system in the urodele seems to be sensory integration, suggesting that the orexin-A nervous system is associated with the modulation of sensory inputs. Orexin-A immunoreactive puncta were also observed on catecholaminergic and serotonergic somata. In view of the restricted somatic distribution in the hypothalamus, wide distribution of fibers throughout the central nervous system (CNS), and intimate association with monoaminergic somata, the orexin nervous system in the axolotl CNS is similar to those of other vertebrates, suggesting that this system is essential for brain functions throughout vertebrates.

Centrifugal neurons of the octopus optic lobe cortex are immunopositive for calcitonin gene-related peptide.

Distribution of calcitonin gene-related peptide (CGRP)-like substance in the optic lobe cortex and retina of the octopus was examined immunohistochemically. Wheat germ agglutinin (WGA), a retrograde-transporting marker, was also used to label the centrifugal neurons. CGRP-immunoreactive (CGRP-IR) somata were seen in the inner granular cell layer, but not in the outer granular cell layer or the retina. CGRP-IR fibers were seen not only in the optic lobe cortex, but also in the retinal nerve plexus. Retrogradely labeled somata were seen in the inner granular cell layer, but not in the outer granular cell layer. Immunohistochemical double staining indicated that WGA-labeled centrifugal neurons were immunopositive for CGRP. These results suggested that the centrifugal neurons in the octopus optic lobe cortex are CGRP-like peptide-containing neurons, and that the peptide may modulate photoreceptor cell functions.

Galanin-immunoreactive neuronal system and colocalization with serotonin in the optic lobe and peduncle complex of the octopus (Octopus vulgaris)

Immunohistochemical techniques were used to investigate the distribution of galanin-like immunoreactivity and colocalization with serotonin (5-HT) in the optic lobe and peduncle complex of the octopus, Octopus vulgaris. Galanin immunoreactive (Gal-IR) fibers, but not cells, were seen in the plexiform layer of the optic lobe cortex. Gal-IR cells were scattered in the cell-islands of the optic lobe medulla and Gal-IR varicose fibers were observed to be abundant in the neuropil surrounding the islands. All Gal-IR cells were immunoreactive for 5-HT, and a few cells showed only 5-HT-like immunoreactivity. In the peduncle lobe, no Gal-IR cells were seen in the basal zone or spine, but in the basal zone, many Gal-IR fibers were seen. In the anterior olfactory lobule, only a few pyramidal Gal-IR cells were observed in the cell layer, and their apical processes were traced to the central neuropil. In the median olfactory lobule, ovoid Gal-IR cells were scattered in the peripheral cell layer. All Gal-IR cells in the anterior and median olfactory lobules showed 5-HT-like immunoreactivity. In the posterior olfactory lobule, ovoid and triangular Gal-IR cells were scattered in the cell layer. Some of them showed 5-HT-like immunoreactivity. Western blot analysis indicated an Gal-IR band at approximately 15.4 kDa. These results suggest the association of galanin-like substance and 5-HT with the visual system of octopus and that the main form of the octopus galanin might have a different molecular weight from vertebrate galanins.

Orexin-B-like immunoreactivity localized in both luteinizing hormone-and thyroid-stimulating hormone-containing cells in the Nile tilapia (Oreochromis niloticus) pituitary

Immunohistochemical techniques were employed to examine orexin-like immunoreactivities in the pituitary of the Nile tilapia (Oreochromis niloticus). Rabbit anti-orexin-A serum and mouse anti-orexin-B monoclonal antibodies were used as primary antibodies. Orexin-B immunoreactive cells corresponded to luteinizing hormone (LH)- or thyroid-stimulating hormone (TSH)-containing cells, and all LH- and TSH-containing cells were immunoreactive for orexin-B. However, we found no orexin-A immunoreactive cells in the pituitary. In the Nile tilapia, an orexin-B-like substance may be secreted from LH- or TSH-containing cells and may regulate pituitary function, rather than the orexin-A-like substance in the pituitaries of Japanese seaperch and medaka.

Localization of corticotropin-releasing factor-immunoreactive nervous tissue and colocalization with neuropeptide Y-like substance in the optic lobe and peduncle complex of the octopus (Octopus vulgaris)

The distribution of corticotropin-releasing factor (CRF)-like immunoreactivity and its colocalization with neuropeptide Y (NPY)-like substances were investigated in the optic lobe and peduncle complex of the octopus (Octopus vulgaris) using immunohistochemical techniques. In the optic lobe cortex, CRF-immunoreactive (CRF-IR) and NPY-immunonegative varicose fibers were observed in the plexiform layer. In the medulla, CRF-IR somata were seen in the cell islands, and CRF-IR varicose fibers were observed in the neuropil. About half of the CRF-IR structures in the medulla showed NPY-like immunoreactivity. In the peduncle lobe, no CRF-IR somata but abundant CRF-IR varicose fibers were observed, and about half of them showed NPY-like immunoreactivity. In the olfactory lobe, CRF-IR somata and abundant CRF-IR varicose fibers were observed. Almost all the CRF-IR somata located in the posterior olfactory lobule showed NPY-like immunoreactivity, whereas those seen in the median olfactory lobule were immunonegative for NPY. About half of the CRF-IR fibers in the anterior lobule neuropil were immunopositive for NPY, but those in the median and posterior lobule neuropils were immunonegative for NPY. In the optic gland, almost all the CRF-IR varicose fibers were immunoreactive for NPY. Western blot analysis of the optic lobe and peduncle complex indicated that anti-CRF antiserum labeled approximate 16.4- and 14.6-kDa bands and that anti-NPY antiserum labeled an approximate 16.2-kDa band. CRF-IR and NPY-immunoreactive neurons in the optic lobe may participate in the modulation of visual information and those in the optic gland may be involved in the regulation of endocrine function.

Orexin-B-like immunoreactivity localizes in both luteinizing-hormone-containing cells and melanin-concentrating hormone-containing fibers in the red-bellied piranha ( Pygocentrus nattereri ) pituitary

We examined orexin-like immunoreactivity in the pituitary of the red-bellied piranha (Pygocentrus nattereri). Orexin-B-immunoreactive (IR) cells corresponded to luteinizing hormone (LH)-containing cells in the pars distalis, and orexin-B-IR fibers corresponded to melanin-concentrating hormone (MCH)-containing fibers in the pars nervosa. In the pars distalis, orexin-B-IR puncta that were also immunoreactive for MCH were observed around the orexin-B-IR cells. In the ventral hypothalamus, orexin-B-IR and MCH-IR neurons were found in the nucleus lateralis tuberis. Immunoelectron-microscopic analysis revealed that the orexin-B-like substance co-localized with LH in secretory granules and with MCH in MCH-containing neurons. Some of the MCH secreted in the pituitary might participate in the modulation of LH secretion from the gonadotrophs, together with orexin-B, leading to food intake by the stimulation of growth hormone secretion from the somatotrophs.

Ghrelin- and growth hormone secretagogue receptor-immunoreactive cells in Xenopus pancreas

Ghrelin and its receptor, growth hormone secretagogue receptor (GHS-R), are produced by various cell types and affect feeding behavior, metabolic regulation, and energy balance. In the mammalian pancreas, the types of endocrine cells immunoreactive for ghrelin vary. Further, no study has clarified the type of endocrine cells producing ghrelin and GHS-R in the non-mammalian pancreas. We immunohistochemically investigated ghrelin-like and GHS-R-like immunoreactivities in the Xenopus pancreas. Ghrelin-immunoreactive cells were observed both in islets and extrainsular regions, and they corresponded to insulin-containing cells. GHS-R-immunoreactive cells were observed in the islets, and these immunoreactive cells corresponded to insulin- and somatostatin-containing cells. These observations suggest that ghrelin is co-secreted with insulin and that ghrelin may act in an autocrine fashion for insulin-containing cells and in a paracrine fashion for somatostatin-containing cells in this species.

CXCL14-Like Immunoreactivity Exists in Somatostatin-Containing Cells of Mouse Pancreas

Immunohistochemical techniques were employed to investigate the distribution of the chemokine CXCL14, in the mouse pancreas. CXCL14-immunoreactive cells were detected in the peripheral region of the pancreatic islets and were immunoreactive for somatostatin, but not for glucagon, insulin, and pancreatic polypeptide. Immunoelectron microscopy indicated that the CXCL14-like peptide and somatostatin co-existed in the secretory granules. CXCL14, secreted from somatostatin-containing cells, may modulate insulin secretion in a paracrine fashion, and play a novel role in glucose homeostasis in addition to its well-known chemotactic activities.