Preopticus Magnocellularis Research Articles

Neuroanatomical localization of nitric oxide synthase (nNOS) in the central nervous system of carp, Labeo rohita during post-embryonic development

Nitric oxide (NO) is a chemically diffusible molecular messenger playing various roles in both vertebrates and invertebrates. Nitric oxide synthase (NOS) is the key enzyme in synthesis of NO. The neuroanatomical distribution pattern of neuronal nitric oxide synthase (nNOS) was studied and developing stages of Labeo rohita such as hatchlings (10–15mm), frys (15–35mm), semi-fingerlings (35–65mm), fingerlings (65–100mm) and adults (350–370mm) were used. In the telencephalon, nitrergic cells were observed in both pallial and subpallial regions along with entopeduncular nucleus suggesting the involvement of NO in the control of sensory functions throughout the development. In the diencephalon, nNOS positive neurons were localized in the nucleus preopticus periventricularis and preopticus parvocellularis throughout development while nucleus preopticus magnocellularis was found immunopositive only in adult specimens who suggest the involvement of NO in the hormonal regulation. nNOS immunoreaction was also noted in suprachaismatic nucleus, habenula, lateral tuberal nucleus, paraventricular organ and anterior division of preglomerular nucleus throughout development. In the mesencephalic region, nNOS immunoreactivity was seen in the optic tectum, torus longitudinalis, nucleus of median longitudinal fascicle and occulomotor nucleus indicate the role of NO in integration of visual inputs and modulates motor control of the eyes and movements. Caudally, in the rhombencephalon, the cerebellum, the nucleus reticularis, the octaval nucleus and the motor nucleus of vagal nerve were nNOS positive during development. nNOS reactive cells and fibers were noted in the spinal motor column, thus suggesting a role of NO in gestation and startle response from early development.

Expression of GnRH genes is elevated in discrete brain loci of chum salmon before initiation of homing behavior and during spawning migration

Our previous studies suggested the importance of gonadotropin-releasing hormones (GnRHs) for initiation of spawning migration of chum salmon, although supporting evidence had been not available from oceanic fish. In farmed masu salmon, the amounts of salmon GnRH (sGnRH) mRNAs in the forebrain increased in the pre-pubertal stage from winter through spring, followed by a decrease toward summer. We thus hypothesized that gene expression for GnRHs in oceanic chum salmon changes similarly, and examined this hypothesis using brain samples from winter chum salmon in the Gulf of Alaska and summer fish in the Bering Sea. They were classified into sexually immature and maturing adults, which had maturing gonads and left the Bering Sea for the natal river by the end of summer. The absolute amounts of GnRH mRNAs were determined by real-time PCRs. The amounts of sGnRH mRNA in the maturing winter adults were significantly larger than those in the maturing summer adults. The amounts of sGnRH and chicken GnRH mRNAs then peaked during upstream migration from the coast to the natal hatchery. Such changes were observed in various brain loci including the olfactory bulb, terminal nerve, ventral telencephalon, nucleus preopticus parvocellularis anterioris, nucleus preopticus magnocellularis and midbrain tegmentum. These results suggest that sGnRH neurons change their activity for gonadal maturation prior to initiation of homing behavior from the Bering Sea. The present study provides the first evidence to support a possible involvement of neuropeptides in the onset of spawning migration.

Organization of Olfactory System, Forebrain and Pituitary Gland of a Teleost, Notopterus Notopterus

Background: The olfactory organ, forebrain and pituitary gland are important in the regulation of reproduction. The fish N. notopterus was selected for the present study for it provided the opportunity to study reproduction having a single gonad in the body. Purpose: To study the nuclear identification of olfactory system, forebrain and pituitary gland in Notopterus notopterus using Kluver and Barrera and Aldehyde fuschin staining techniques. Methods : Notopterus notopterus fishes were perfused transcardially with PBS followed by the same volume of Bouin's fixative. Olfactory organ with bulb and brain with pituitary gland were dissected out and post-fixed in the same fixative overnight. The olfactory organ and brain with pituitary gland were cut at 10 mm thickness in transverse as well as sagittal plane. Kluver and Barrera and Aldehyde fuschin staining techniques were used to study the tissue sections. Results: In the forebrain, multipolar cells of nucleus entopeduncularis (NE) were located in the telencephalon. Diencephalon was divided into preoptic area, hypothalamus, thalamus and epithalamus. In the diencephalon, Suprachiasmatic nucleus (SCN), Nucleus preopticus (NPO) and nucleus anterior commissure (NAC) were also identified. In the preoptic area, nucleus of subventricular gray (NSG) and organasum vasculossum lamellae terminalis (OVLT) was observed. Nucleus preopticus magnocellularis (NPOm) is the only AF-positive nucleus in the neuronal complex. Caudal to preoptic region, the tuberal area starts which has nucleus hypothalmicus (Nh) and nucleus lateralis tuberis (NLT). Above the hypothalamus, thalamic area shows thalamic nuclei. In the epithalmus, paired habenular ganglia were connected to each other by habenular commissure. Conclusion: This study will helpful to find out the correlation of brain and pituitary gland in the order Osteoglossiformes. doi: 10.5214/ans.0972.7531.2008.150204 Competing interests: None. Source of Funding: None Received Date: 18 April 2008 Revised Date: 29 April 2008 Accepted Date: 03 May 2008

Elevation of gene expression for salmon gonadotropin-releasing hormone in discrete brain loci of prespawning chum salmon during upstream migration

Our previous studies suggested that salmon gonadotropin-releasing hormone (sGnRH) neurons regulate both final maturation and migratory behavior in homing salmonids. Activation of sGnRH neurons can occur during upstream migration. We therefore examined expression of genes encoding the precursors of sGnRH, sGnRH-I, and sGnRH-II, in discrete forebrain loci of prespawning chum salmon, Oncorhynchus keta. Fish were captured from 1997 through 1999 along their homing pathway: coastal areas, a midway of the river, 4 km downstream of the natal hatchery, and the hatchery. Amounts of sGnRH mRNAs in fresh frozen sections including the olfactory bulb (OB), terminal nerve (TN), ventral telencephalon (VT), nucleus preopticus parvocellularis anterioris (PPa), and nucleus preopticus magnocellularis (PM) were determined by quantitative real-time polymerase chain reactions. The amounts of sGnRH-II mRNA were higher than those of sGnRH-I mRNA, while they showed similar changes during upstream migration. In the OB and TN, the amounts of sGnRH mRNAs elevated from the coast to the natal hatchery. In the VT and PPa, they elevated along with the progress of final maturation. Such elevation was also observed in the rostroventral, middle, and dorsocaudal parts of the PM. The amounts of gonadotropin IIbeta and somatolactin mRNAs in the pituitary also increased consistently with the elevation of gene expression for sGnRH. These results, in combination with lines of previous evidence, indicate that sGnRH neurons are activated in almost all the forebrain loci during the last phases of spawning migration, resulting in coordination of final gonadal maturation and migratory behavior to the spawning ground.

Developmental expression of three forms of gonadotropin-releasing hormone and ontogeny of the hypothalamic-pituitary-gonadal axis in gilthead seabream (Sparus aurata).

To address the complexity of the origin of the GnRH system in perciforms, we investigated the ontogenic expression of three GnRHs in gilthead seabream. Using in situ hybridization, chicken (c) GnRH-II mRNA-expressing cells were detected in the hindbrain at 1.5 days postfertilization (DPF) and in the midbrain at 2 DPF and thereafter; the hindbrain signals became undetectable after 10 DPF. Salmon (s) GnRH mRNA-expressing cells were first seen in the olfactory placode at 3 DPF, started caudal migration at 14 DPF, and reached the preoptic areas at 59 DPF. Seabream (sb) GnRH mRNA-expressing cells were first detected in the terminal nerve ganglion cells (TNgc), ventral part of the ventral telencephalon, nucleus preopticus parvocellularis, and thalamus at 39 DPF, and extended to the nucleus preopticus magnocellularis at 43 DPF, ventrolateral hypothalamus at 51 DPF, and nucleus lateralis tuberis and posterior tuberculum at 59 DPF. Coexpression of sbGnRH and sGnRH transcripts was found in the TNgc. Using real-time fluorescence-based quantitative polymerase chain reaction, transcript levels of cGnRH-II and sGnRH were first detected at 1 and 1.5 DPF, respectively, and increased and remained high thereafter. Transcript levels of sbGnRH remained low after first detection at 1 DPF. Furthermore, these GnRH expression profiles were correlated with the expression profiles of reproduction-related genes in which at least four concomitant increases of GnRH, GnRH receptor, gonadotropin, gonadotropin receptor, and Vasa transcripts were found at 5, 8, 14, and 28 DPF. Our data provide an expanded view of the ontogeny of the GnRH system and reproductive axis in perciforms.

Neural circuits and their structural and chemical reorganization in the light–brain–pituitary axis during parr–smolt transformation in salmon

Salmonid parr–smolt transformation (smoltification) is a transitional stage between freshwater and seawater life when the salmon imprint on their natal stream, change from a territorial feeding behavior to downstream migration, increase their hypoosmoregulatory competence, and change body shape and coloration. Photoperiod is recognized as the most potent initiator and regulator of the smoltification processes. Environmental light signals giving information about photoperiod are conveyed through a light–brain–pituitary axis that encompasses the neural pathways between photoreceptor organs, the brain and the pituitary, and the diurnal rhythm in melatonin secretion by the photosensory pineal organ. In addition, changes in photoperiod may elicit changes in this axis. Employing retinal neural tract tracing and growth associated protein-43 (GAP-43) immunocytochemistry, we provide here new evidence of a structural reorganization in the light–brain–pituitary axis during smoltification. Retinal tract tracing revealed that projections in smolts expand into new territories of the ipsilateral nucleus preopticus parvocellularis pars anterior (PPa) and additional fibers invade deeper into the contralateral PPa and the nucleus preopticus magnocellularis (PM). At this time, GAP-43-immunoreactive cells appear transiently in specific cell groups throughout the brain, but mainly in the olfactory bulb, telencephalon, and hypothalamus. These structural changes in the light–brain–pituitary axis and hypophysiotropic systems are followed by sequential surges of brain neurotransmitters and receptors, and occur prior to the major surges of circulating thyroid hormone and growth hormone levels that are central to smoltification-related processes. Our data point to a specific period of structural reorganization in certain brain circuits, and we hypothesize that these are involved in triggering the subsequent behavioral, endocrine, and physiological changes associated with smoltification.

Vertebrate ancient (VA) opsin and extraretinal photoreception in the Atlantic salmon (Salmo salar).

A member of a new photopigment family first isolated from teleost fish, vertebrate ancient (VA) opsin, has recently been shown to form a functional photopigment and to be expressed within a subset of horizontal and amacrine cells of the inner retina. These sites of expression (and structural features) of VA opsin suggest that this photopigment might mediate non-image-forming light-detection tasks. We attempted to gain support for this hypothesis by examining the expression of VA opsin within the central nervous system (CNS) (pineal and deep brain) of the Atlantic salmon Salmo salar. In addition, we examined the sites of rod-opsin, cone-opsin and &agr; -transducin expression within the salmon CNS to provide a more complete description of the extraretinal photoreceptors of a teleost vertebrate. We show that multiple populations of cells within the salmon CNS appear to contain photoreceptors: VA opsin was strongly expressed in the pineal organ and in bilateral columns of subependymal cells in the epithalamus; anti-cone-opsin antibodies labelled cells within the pineal and numerous cells in the anterior hypothalamus (suprachiasmatic nucleus, nucleus preopticus magnocellularis, nucleus preopticus parvocellularis); anti-rod-opsin antibodies labelled cells within the pineal but no other areas within the central brain; and anti- &agr; -transducin antibodies labelled cells within the pineal and the ventral telencephalon. Collectively, our results suggest that VA opsin is a photopigment specialised for irradiance detection tasks within the eye, pineal and central brain, and that the salmon has multiple and varied populations of photoreceptors within the CNS. We review the significance of these findings within the broad context of vertebrate extraretinal photoreception.

Distribution of β-amyloid and amyloid precursor protein in the brain of spawning (senescent) salmon: a natural, brain-aging model

Brain amyloid precursor protein (APP), a normal constituent of neurons, glial cells and cerebrospinal fluid, has several proposed functions (e.g., in neuronal growth and survival). It appears, however, that altered processing of APP is an initial or downstream step in the neuropathology of brain aging, Alzheimer's disease (AD), and Down's syndrome (DS). Some studies suggest that proteolytic cleavage of APP, producing β-amyloid (Aβ 1–42), could have neurotoxic or neuroprotective effects. In this study, we utilized antibodies to human APP 695 and Aβ 1–42, and Congo red staining, to search for amyloid deposition in the brain of semelparous spawning kokanee salmon ( Oncorhynchus nerka kennerlyi). Intracellular APP 695 immunoreactivity (APP-ir) was observed in brain regions involved in gustation (glomerulosus complex), olfaction (putative hippocampus, olfactory bulb), vision (optic tectum), the stress response (nucleus preopticus and nucleus lateralis tuberis), reproductive behavior (nucleus preopticus magnocellularis, nucleus preopticus periventricularis, ventral telencephalon), and coordination (cerebellum). Intra- and extra-neuronal Aβ 1–42 immunoreactivity (Aβ-ir) were present in all APP-ir regions except the nucleus lateralis tuberis and Purkinje cells of the cerebellum (coordination). Thus, the relationship between APP and Aβ deposition during brain aging could shed light on the processing of APP into Aβ, neurodegeneration, and possible protection of neurons that are functioning in spawning but senescent salmon. Pacific salmon, with their predictable and synchronized life history, could provide research options not available with the existing models for studies of brain aging and amyloidosis.

Localization of mRNA Encoding Thyrotropin-Releasing Hormone Precursor in the Brain of Sockeye Salmon

Abstract The distribution of mRNA encoding thyrotropin-releasing hormone (TRH) precursor in the brain of sockeye salmon was studied by in situ hybridization histochemistry using digoxigenin-labeled riboprobes as a basis to investigate its physiological functions in the salmon brain. Since seasonal variation in TRH gene expression was expected in relation to smolting or maturation, fish were sampled in February and October. In both groups, TRH mRNA was widely distributed in discrete brain regions including the internal cellular layer (ICL) of the olfactory bulb, postcommissural nucleus of area ventralis telencephali (Vp), nucleus preopticus parvocellularis anterioris (PPa), nucleus preopticus magnocellularis, dorsal zone of periventricular hypothalamus (Hd), torus semicircularis, and also the motor nucleus of vagus nerve in the medulla oblongata. TRH neurons in ICL and Hd are round and small with diameters of 5–10 μm. In contrast, TRH neurons in the ventral telencephalon and the preoptic area are medium-si...

Periventricular morphology in the diencephalon of antarctic notothenioid teleosts

We have examined the subependymal region of the diencephalic third ventricle in notothenioid perciforms and report a pattern of neuropil expansions that appears to be phyletically derived for notothenioids and their outgroups but that is otherwise unique among vertebrates. We recognize five types of expansions based on their composition (from less dense neuropil to sacs) and width or protrusion into the third ventricle. In the species with the most elaborate morphology, Trematomus bernacchii, bilateral subependymal expansions fuse along the midline to form a single sac within the ventricular cavity. The extent of these expansions loosely corresponds with phyletic position but also (and perhaps more importantly) is correlated with the habitation of cold water (r2 = 0.48; P = 0.012). Furthermore, subependymal expansion type is positively correlated with the maximum size of the soma of neurons in two hypothalamic nuclei, the preopticus magnocellularis (r2 = 0.54; P = 0.006) and the lateralis tuberis (r2 = 0.40; P = 0.038). These nuclei project to the pituitary and contain cerebrospinal fluid-contacting neurons. In considering the functional consequences of this morphology, we cannot dismiss the possibility that these structures form a specialized enteroceptive system tied to the monitoring of cerebrospinal and extracellular fluid components, including antifreeze glycopeptides and inorganic ions.

NADPH‐Diaphorase in the central nervous system of the tench (tinca tinca L., 1758)

The distribution and morphological characterization of nicotinamide adenine dinucleotide phosphate-diaphorase (ND)-positive cells and fibers in the tench central nervous system was mapped by using a direct histochemical method. This enzyme was observed in specific cell populations throughout all main divisions of the tench brain. In the telencephalon, we found strongly labeled olfactory fibers, as well as positive cells and fibers in the area ventralis of the telencephalic lobes. Positive staining was observed in the following diencephalic nuclei: nucleus preopticus magnocellularis pars magnocellularis, nucleus recessus lateralis, nucleus recessus posterioris, nucleus posterior tuberis, and nucleus diffusus torus lateralis, as well as small cells with a diffuse distribution surrounding the diencephalic ventricle. In the mesencephalon, heavily stained ND-positive neurons were observed in the nucleus fasciculi longitudinalis medialis, nucleus nervi oculomotorius, and nucleus nervi trochlearis. In the hindbrain the most evident staining was observed as large neurons located in the nuclei of the cranial nerves, scattered positive cells located between the negative fibers of the cranial nerves, and in the nucleus fasciculi solitari. Finally, in the spinal cord, ND-positive cells and fibers were mainly located in the ventral horn. This distribution of ND labeling in the brain of the tench is significantly different from previous data on ND activity in the brain of terrestrial vertebrates and does not correlate with the presence and distribution patterns of several neurotransmitters and neuroactive substances in the teleost brain.

Topographic organization of descending projection neurons to the spinal cord of the goldfish, Carassius auratus

Several neurons from different nuclei give rise to descending spinal tracts and project to various levels in the spinal cord of goldfish, Carassius auratus. These were visualized by retrograde transport of horseradish peroxidase (HRP) administered to the bilaterally transected spinal cord at 6 levels, corresponding to 1st, 5th, 10th, 15th, 20th and 25gh segments of the vertebral column. As many as 16 brain nuclei or neuronal aggregations and the Mauthner cells project posteriorly up to the 20th spinal segment. Restricted neurons of the dorsolateral area in the nucleus preopticus magnocellularis and those of the ventromedial nucleus of the thalamus projected up to the 20th and 25th segments respectively. In the mesencephalon, the nucleus ruber and the nucleus of the medial longitudinal fasciculus revealed retrogradely labeled somata; the former extended up to the 20th segment, while the latter projected up to the 25th segment. The remaining descending projected neurons of the brain belonged to the rhombencephalon. The nucleus of the lateral lemniscus; anterior, magnocellular, descending and posterior divisions of the octaval nucleus: raphe nucleus; Mauthner cell and the neurons located adjacent to the trigeminal tract and those in the vicinity of the secondary gustatory tract sent their processes up to 20th segmental level. However, somata of the superior, medial and inferior divisions of the reticular nucleus and restricted neurons of the facial lobe extended up to 25th segmental level. The pattern of neuronal projections into the spinal cord suggests a topographic organization.

Changes in expression of provasotocin and proisotocin genes during adaptation to hyper- and hypo-osmotic environments in rainbow trout

The physiological roles of neurohypophysial hormones, vasotocin (VT) and isotocin (IT), are not yet clear in teleosts. Since information on responsiveness of hypothalamic neurosecretory neurons to environmental stimuli may contribute to an understanding of their physiological roles, effects of environmental hyper- and hypo-osmotic stimuli on expressions of VT and IT precursor (proVT and proIT) genes in rainbow trout were investigated, using an in situ hybridization technique in which 46 mer synthetic oligonucleotides were used as hybridization probes. The probes corresponded to the mRNA loci encoding chum salmon proVT (-5 to 11) and proIT (-5 to 11), and were labeled at the 3'-end with 35S. Autoradiographic silver grains which represent the hybridization signals of proVT and proIT mRNAs were localized in both magnocellular and parvocellular neurons in the nucleus preopticus magnocellularis (NPOmg). Localizations of proVT and proIT hybridization signals coincided with those of VT- and IT-immunoreactive neurons in adjacent sections, and showed that proVT and proIT genes are expressed in separate neurons. The intensity of proVT hybridization signals as determined by grain counting in magnocellular neurons in the NPOmg was conspicuously decreased after transfer from fresh water (FW) to 80% seawater (SW). The proVT mRNA levels in SW trout were consistently lower than those of FW trout for up to 2 weeks. After return from 80% SW to FW, the proVT mRNA level increased, attaining the initial FW level. The proIT mRNA levels in SW trout were not statistically different from those in FW trout, except for the 1st day after transfer to SW.(ABSTRACT TRUNCATED AT 250 WORDS)

Descending projection neurons to the spinal cord of the goldfish, Carassius auratus.

The sources of descending spinal tracts in the goldfish, Carassius auratus, were visualized by retrograde transport of horseradish peroxidase (HRP) administered to the hemisected spinal cord. In the diencephalon, HRP-positive neurons were identified in the nucleus preopticus magnocellularis pars magnocellularis and ventromedial nucleus of the thalamus of the ipsilateral side. In the mesencephalic tegmentum, a few somata of the contralateral nucleus ruber and several ipsilateral neurons of the nucleus of the median longitudinal fasciculus were labeled. The reticular formation of the rhombencephalon was the major source of descending afferents to the spinal cord. A larger number of neurons were retrogradely labeled in the ipsilateral superior, middle, and inferior nuclei than in the contralateral nuclei. A few raphe neurons and the contralateral Mauthner neuron were also HRP-positive. The octaval area showed retrogradely labeled neurons in the anterior, magnocellular, descending, and posterior octaval nuclei of the ipsilateral side. A large number of neurons in the facial lobe and a few somata located adjacent to the descending trigeminal tract were labeled on the ipsilateral side. The pattern of descending spinal projections in goldfish is comparable to that of tetrapods and suggests that the spinal tracts have originated quite early in the course of vertebrate evolution.

Cholinergic projections from the basal forebrain to frontal, parietal, temporal, occipital, and cingulate cortices: A combined fluorescent tracer and acetylcholinesterase analysis

BIGL, V., N. J. WOOLF AND L. L. BUTCHER. Cholinergic projections from the basal forebrain to frontal, parietal, temporal, occipital, and cingulate cortices: A combined fluorescent tracer and acetylcholinesterase analysis. BRAIN RES. BULL. 8(6) 727–749, 1982.—The morphologies, intercellular organization, and cortical projection patterns of putative cholinergic neurons in the basal forebrain of the rat were examined by use of fluorescent tracer histology in combination with the pharmacohistochemical regimen for acetylcholinesterase (AChE). Intensely staining AChE-containing cells projecting to frontal sensorimotor (Area 10), parietal (Area 2), and temporal (Area 41) cortices were found ipsilaterally in nucleus preopticus magnocellularis, in nucleus basalis, and in association with the substantia innominata, the ansa lenticularis, and the lateral hypothalamic area; an essentially rostrocaudal topography was observed for these projections. AChE-containing pathways to cingulate (Area 29) and visual (Area 17) cortices derived from ipsilateral somata associated with the vertical and horizontal limbs of the diagonal band, nucleus preopticus magnocellularis, rostral portions of nucleus basalis, and the substantia innominata. Neurons innervating Area 29 were generally located more rostrally than those giving rise to AChE afferents to Area 17. The vast majority of cells appeared to innervate relatively discrete areas of the cortex. Evidence for collateralization was found only in neurons projecting to visual and cingulate cortices, and these represented only 3.2% of the cells providing AChE afferents to Areas 17 and 29. The basal forebrain AChE projection cells were typically large (>25 μm in maximum cell body extent), and their somata were predominantly oval, with lesser proportions being fusiform or triangular. Many were organized in clusters, particularly in nucleus basalis.

Hypothalamo-hypophysial Neurosecretory System in Normal and Hypophysectomised Catfish,Clarias Batrachus L

Two neurosecretory centers, nucleus preopticus (NPO) and nucleus lateralis tuberis (NLT), are distinguished in the hypothalamus of Clarias batrachus L. The cell bodies of NPO are grouped into nucleus preopticus magnocellularis (NPM) and nucleus preopticus parvocellularis (NPP). The NLT is recognised into three divisions: pars rostralis, pars medialis and pars ventrolateralis. The neurons of both the NLT and NPO are aldehyde-fuchsin (AF) positive. The axons from NPO run into four or five bundles ventrolaterally and caudally for some distance before all of them from either side join ventromedially into a single thick cord of neurosecretory fibers which finally enters the pars intermedia to form the neurointermediate lobe. The fibers from NLT, which are separate from the neurosecretory fibers of the NPO, anastomose in the region of the pars distalis. The neurosecretory material (NSM) of NPO is transported by axonal route whereas that of NLT is by axonal as well as ependymovascular pathways. Hypophysectomy results in the increase of AF-positive material in the neurons of NPO shortly after the operation, but later on, the material begins to deplete in them. The AF-positive material at the cut end of neurosecretory fibers, however, accumulates. The AF-positive material in the cell bodies of NLT is also depleted, but the nuclei increase in size, after hypophysectomy.