Distribution of catecholaminergic and serotoninergic systems in forebrain and midbrain of the newt,Triturus alpestris (Urodela)

Summary Mapping of monoaminergic systems in the brain of the newt Triturus alpestris was achieved with antisera against (1) thyrosine hydroxylase (TH), (2) formaldehyde-conjugated dopamine (DA), and (3) formaldehyde-conjugated serotonin (5-HT). In the telencephalon, the striatum was densely innervated by a large number of 5-HT-, DA-and TH-immunoreactive (IR) fibers; IR fibers were more scattered in the amygdala, the medial and lateral forebrain bundles, and the anterior commissure. In the anterior and medial diencephalon, TH-IR perikarya contacting the cerebrospinal fluid (CSF-C perikarya) were located in the preoptic recess organ (PRO), the organum vasculosum laminae terminalis and the suprachiasmatic nucleus. Numerous TH-IR perikarya, not contacting the CSF, were present in the posterior preoptic nucleus and the ventral thalamus. At this level, DA-IR CSF-C neurons were only located in the PRO. In the posterior diencephalon, large populations of 5-HT-IR and DA-IR CSF-C perikarya were found in the paraventricular organ (PVO) and the nucleus infundibularis dorsalis (NID); the dorsal part of the NID additionally presented TH-IR CSF-C perikarya. Most regions of the diencephalon showed an intense monoaminergic innervation. In addition, numerous TH-IR, DA-IR and 5-HT-IR fibers, orginating from the anterior and posterior hypothalamic nuclei, extended ventrally and reached the median eminence and the pars intermedia of the pituitary gland. In the midbrain, TH-IR perikarya were located dorsally in the pretectal area. Ventrally, a large group of TH-IR cell bodies and some weakly stained DA-IR and 5-HT-IR neurons were observed in the posterior tuberculum. No dopaminergic system equivalent to the substantia nigra was revealed. The possible significance of the differences in the distribution of TH-IR and DA-IR neurons is discussed, with special reference to the CSF-C neurons.Abbreviations AM amygdala - CAnt commissura anterior - CH commissura hippocampi - CP commissura posterior - Ctm commissura tecti mesencephali - DH dorsal hypothalamus - DTh dorsal thalamus - FLM fasciculus longitudinalis medialis - Fsol fasciculus solitarius - H habenula - LFB lateral forebrain bundle - ME median eminence - MFB medial forebrain bundle - NID nucleus infundibularis dorsalis - nIP neuropil of nucleus interpeduncularis - NPOP nucleus preopticus posterior - NS nucleus septi - OVLT organum vasculosum laminae terminalis - PD pars distalis - Pdo dorsal pallium - PHi primordium hippocampi - PI pars intermedia - Pl lateral pallium - PN pars nervosa - PRO preoptic recess organ - Ptec pretectal area - PVO paraventricular organ - Ra nucleus raphe - Rm nucleus reticularis medius - SCO subcommisural organ - ST striatum; strm stria medullaris thalami - strt stria terminalis thalami - TM tegmentum mesencephali - TO tectum opticum - TP tuberculum posterius - trch tractus cortico-habenularis - trmp tractus mamillopeduncularis - VH ventral hypothalamus - Vm nucleus motorius nervi trigemini - VTh ventral thalamus - II optic nerve     

Seasonal changes in the number of neurocytes containing lipofuscin pigment in selected areas of the brain of Rana temporaria L

The number of neurocytes containing lipofuscin pigment (LEP) was determined in the nucleus infundibularis dorsalis (NID), the subfornical organ (SFO) and the medulla oblongata (MO) of the brain of sexually mature females and males of Rana temporaria L. approximately identical in length and age. The frogs were captured in their natural habitat in seven periods of the annual cycle. The number of LFP-positive neurocytes shows distinct seasonal variations in the analyzed areas. In general, neurocytes containing LFP were found in higher numbers during the winter months, and their significant drop was observed in summer. The results seem to suggest that cells containing LFP represent a certain kind of dynamic cellular system responding to various internal and/or external factors changing within a year.     

The nucleus raphe dorsalis of the rat and its projection upon the caudatoputamen. A combined cytoarchitectonic, immunohistochemical and retrograde transport study

The nucleus raphe dorsalis of the albino rat has been studied in the following three ways: (1) the cell mass was subjected to a detailed cytoarchitectonic analysis, based upon Nissl-stained material; (2) serotonin--as well as the noradrenaline--immunoreactive neurons present in the area of the nucleus raphe dorsalis were plotted; (3) following large injections of the fluorescent dye propidium iodide into the caudatoputamen complex, the cells in the nucleus raphe dorsalis projecting to this complex were labeled and subsequently stained with an antibody against serotonin. Cytoarchitectonic analysis showed that three cell types are present within the confines of the nucleus raphe dorsalis: small, medium and large. Moreover, differences in concentrations of cell bodies made it possible to subdivide the nucleus raphe dorsalis into four regions. Immunohistochemical analysis showed that the borders of the serotoninergic cell groups B6 and B7 of DAHLSTROM and FUXE do not coincide with those of the nucleus raphe dorsalis. Serotonin-immunoreactive perikarya in the nucleus raphe dorsalis were categorized as medium and large neurons; noradrenaline-immunoreactive neurons in the nucleus raphe dorsalis do all belong to the category--large neurons. With the combined use of immunofluorescence and fluorescent retrograde tracing, it was found that the projection from the nucleus raphe dorsalis to the caudatoputamen complex originates from serotoninergic as well as non-serotoninergic cells, both of which can be categorized as being medium-sized neurons. The data presented in this paper provides a guide for further studies of afferent and efferent connections of the nucleus raphe dorsalis and for electrophysiological experiments on its constituent neurons.     

Accumulation of lipofuscin in the brain of the frog, Rana temporaria, subjected to treatment with ultrasound

Sexually mature male and female frogs, Rana temporaria L., taken from their natural habitat at the end of the hibernation period, were subjected to treatment with ultrasound of various duration. The ultrasound (frequency, 24 kHz, intensity 0.35 W/cm2) was applied over the whole body in a suitable water bath. Neurons of the nucleus infundibularis dorsalis, medulla oblongata, and the subfornical organ were studied. A considerable increase in the amount of autofluorescent lipofuscin pigment was observed in nerve cells of various regions of the brain of the treated animals. The largest amounts of the lipofuscin pigment were found in those treated for one hour and killed on the fourteenth day following sonication.     

Organization of the telencephalon in the channel catfish,Ictalurus punctatus

The cytoarchitectonics of the telencephalon of the channel catfish, Ictalurus punctatus, are described as a basis for experimental analysis of telencephalic afferents and efferents. The olfactory bulb comprises: (1) an outer layer of olfactory nerve fibers, (2) a glomerular layer, (3) an external cell layer, (4) an inner fiber layer, and (5) an internal cell layer. The telencephalic hemispheres comprise the areas ventralis and dorsalis telencephali. The area ventralis consists of: (1) a precommissural, periventricular zone including nucleus 'nother (Vn), the ventral nucleus (Vv), and the dorsal nucleus (Vd); (2) a precommissural, migrated zone of central (Vc) and lateral (VI) nuclei; (3) a supracommissural nucleus (Vs); (4) a caudal commissural zone of postcommissural (Vp) and intermediate (Vi) nuclei; and (5) a preoptic area (PP). The area dorsalis comprises: (1) medial (DM), (2) dorsal (Dd), (3) lateral [DL, containing dorsal (DLd), ventral (DLv), and posterior (DLp) regions], (4) posterior (DP), and (5) central (DC-1, -2, -3) areas. Nucleus taeniae (NT) is transitional between areas dorsalis and ventralis.     

Comparative distribution of nitric oxide synthase- and serotonin-containing neurons in the raphe nuclei of four mammalian species

 Monoclonal antibodies were generated against serotonin (5-HT) and the C-terminal portion of the neuronal form of nitric oxide synthase (nNOS), the enzyme producing nitric oxide in neurons. These antibodies were used to compare the distribution of 5-HT- and nNOS-containing neurons in the raphe nuclei of four animal species (rat, mouse, guinea pig, and cat). It was found that the rat was the only species in which the raphe nuclei contain a substantial number of nNOS-immunoreactive (IR) cell bodies. In this species and as observed by other authors, all mesencephalic raphe nuclei contained nNOS-IR cells, the largest group being located in the nucleus raphe dorsalis. The coexistence of nNOS and 5-HT immunoreactivities in these nuclei was visualized by double labeling. In the medulla, the nuclei raphe magnus and obscurus displayed a rather low number of nNOS-IR neurons. In the other species, nNOS-IR cell bodies were found in very low numbers, whatever raphe nucleus was considered. The rostral pole of the nucleus raphe dorsalis and the nuclei raphe magnus and obscurus contained a few nNOS-IR neurons which did not show any coincidence with the 5-HT neurons. In addition, nNOS-IR axons were rare. It is concluded that in the mouse, guinea pig, and cat the involvement of nitric oxide in functions subserved by 5-HT within the raphe nuclei might be minimal. Accepted: 5 May 1998     

The distribution of monoamine oxidase and acetylcholinesterase in the brain of Xenopus laevis tadpoles

Summary The distribution of monoamine oxidase (MAO) in the brain of Xenopus laevis tadpoles (stage 52–56) was studied histochemically with a modified Glenner's tryptamine-tetrazolium method. A moderate activity was observed in fibre regions of the striatum and septum (including the medial and lateral forebrain bundles), in the neuropil of the nucleus amygdalae, in the commissura anterior and commissura hippocampi, in the fibre regions of the diencephalon (including the optic chiasma), in the fibre regions of the tectum opticum and the tegmentum of the mesencephalon and in the white substance of the ventral half of the medulla oblongata. A greater MAO activity was found in the neuropil of the entire nucleus praeopticus. In the partes anterior and magnocellularis of this nucleus, MAO positive fibres are present in close contact with the perikarya, indicating a monoaminergic innervation of these neurons. The perikarya themselves did not show MAO activity. In the neurons of the nucleus praeopticus epichiasmaticus, the paraventricular organ (PVO) and nucleus infundibularis dorsalis (NID), only a slight MAO activity has been demonstrated in the perikarya, whereas a strong MAO positivity was found in the intraventricular protrusions and the neuropil. These data indicate the aminergic character of the neurons of these nuclei. From the postoptic fibre region a MAO positive tract was observed towards the developing median eminence and pars intermedia of the hypophysis. The pars nervosa and some cells of the pars distalis also contained MAO. Along the border of the aquaeduct of Silvius and the fourth ventricle, MAO positive liquor-containing neurons are also present.The distribution of acetylcholinesterase (AChE) was investigated in the hypothalamohypophysial region. AChE activity was found in the neuropil of the nucleus praeopticus magnocellularis, in the fibres of the optic chiasma and in the postoptic fibre region. The neurons of the PVO and NID were AChE negative. An AChE positive tract could be traced from the postoptic fibre region to the developing median eminence and pars nervosa. The pars distalis did not show AChE activity. However, in tadpoles reaching the metamorphic climax, ChE activity appeared in certain cells of the pars distalis; this might be related to degenerative phenomena in the acidophilic cells. The absence of AChE activity in the pars intermedia indicates a regulation of MSH release by peptidergic nerves to be unlikely.The stimulating interest and helpful advice of Prof. Dr. P. G. W. J. van Oordt is gratefully acknowledged. Thanks are also due to Mr. H. van Kooten and his co-workers for making the photographs.     

Immunocytochemical localization of a galanin-like peptidergic system in the brain and pituitary of some teleost fish

Summary Immunostaining of brain and pituitary sections of teleost fishes (eels, salmonidae, cyprinidae, gourami, sculpin, mullet) with anti porcine galanin (GAL) revealed the presence of immunoreactive (ir) perikarya and a rich network of fibers. Ir-perikarya were located rostrodorsally to the recessus preopticus, and in the posterior tuberal hypothalamus. Ir-fibers were abundant in basal telencephalon and around diencephalic ventricular recesses but never contacted their lumen. Furthermore, they were observed in basal hypothalamus, brainstem and ventral medulla. Ir-fibers passed along corticotropic (ACTH), gonadotropic cells and somatotropes (GH cells) in eel and trout pars distalis, but rarely ended in caudal neurohypophysis. In goldsfish pituitary ir-fibers occurred in neural digitations and among different cell types which however did not contain a GAL-like peptide. The relation GAL fibers/GH cells appeared more evident in species with a high growth rate. The other species showed a similar distribution of brain GAL. In eels and trout, ir-perikarya were not observed in areas containing somatostatin, GH- and ACTH-releasing factor, and ACTH-like perikarya, suggesting that GAL did not coexist with these peptides. The widespread distribution of a GAL-like peptide in teleost brain suggests that it could play a role of neurotransmitter and/or neuromodulator and regulate the secretion of adenohypophysial hormone(s). Abbreviations used in the text: GAL galanin. In the brain: CSF cerebrospinal fluid; NLT nucleus lateralis tuberis; NPO nucleus preopticus; NPP nucleus preopticus periventricularis; NPVa nucleus periventricularis anterior; NRP nucleus recessus posterioris; RI recessus infundibularis; RL recessus lateralis; RPO recessus preopticus. In the pituitary: ACTH corticotropin; CRF corticotropin-releasing factor; GH growth hormone; GRF growth hormone-releasing factor; GTH gonadotropin; MSH melanotropin; NH neurohypophysis; NIL: neurointermediate lobe; PPD proximal pars distalis; RPD proximal pars distalis     

Immimohistochemical localization of corticotropin-releasing factor in selected brain areas of the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia)

Summary Corticotropin-releasing factor (CRF) was localized in the brains of two passerine species, the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia), by means of immunohistochemistry. The hypothalamic distribution of this peptide in these species includes a complex of immunoreactive perikarya observed in the paraventricular nucleus (PVN), in both its medial and lateral divisions. Nerve fibers were also seen running from these areas to the anterior median eminence (AME) where a terminal field is apparent. A wide variety of extra-hypothalamic nuclei containing CRF-immunoreactive cells and fibers were identified. An apparent CRF terminal field can be visualized in the lateral septum. A dense fiber plexus is present in the nucleus accumbens (Ac) and more caudally in the nucleus of the stria terminalis (nST). In colchicinepretreated animals, it was revealed that these areas also contain CRF-stained perikarya. The pattern of CRF immunoreactivity in the Ac-nST complex is continuous, with no distinction apparent between the nuclei. The medial preoptic area (mPOA) and the adjacent diagonal band of Broca contain CRF-fibers, while cells are apparent in the mPOA. In the mesencephalon, cells were visualized in the midbrain central gray; a terminal field and scattered positively stained perikarya were found in areas more ventral to the central grey that are adjacent to the third cranial nerve. Scattered cells were also seen at the border of the nucleus intercollicularis-nucleus mesencephalicus lateralis, pars dorsalis complex. In contrast to mammalian studies, no immunoreactive nerve fibers or perikarya were observed in telencephalic areas homologous to the mammalian neocortex. These studies confirm the presence of a CRF path-way regulating pituitary function and suggest a broad role played by CRF as a neuromodulator or neurotransmitter in autonomic and possibly behavioral activities in these species.     

Substance P-immunoreactive neurons in the brainstem of the cat related to cardiovascular centers

Summary The distribution of substance P-immunoreactivity (SP-IR) in the brainstem and spinal cord of normal and colchicine-pretreated cats was analysed using the peroxidase-antiperoxidase (PAP) technique. Numerous SP-IR fibers are present in the nucleus solitarius, nucleus dorsalis nervi vagi and nucleus spinalis nervi trigemini, various parts of the formatio reticularis, substantia grisea centralis mesencephali, locus coeruleus and nucleus parabrachialis. SP-IR perikarya occur in the substantiae gelatinosa and intermedia of the spinal cord, the nucleus spinalis nervi trigemini-pars caudalis, the nucleus dorsalis nervi vagi, and the nucleus solitarius, as well as in the adjacent formatio reticularis and the medullary nuclei of the raphe. In addition, SP-IR cell bodies are located in the nuclei raphe magnus and incertus, ventral and dorsal to the nucleus tegmentalis dorsalis (Gudden), nucleus raphe dorsalis, substantia grisea centralis mensencephali, locus coeruleus, nucleus parabrachialis and colliculus superior.The results indicate that SP-IR neurons may be involved in the regulation of cardiovascular functions both at the central and peripheral level. A peripheral afferent portion seems to terminate in the nucleus solitarius and an efferent part is postulated to originate from the nucleus dorsalis nervi vagi and from the area of the nuclei retroambiguus, ambiguus and retrofacialis.     

Topographische Verteilung der Monoaminfluoreszenz im Zwischenhirn-Hypophysensystem von Carduelis chloris und Anas platyrhynchos

Zusammenfassung Im Hypothalamus von Grünfink (Carduelis chloris) und Ente (Anas platyrhynchos) zeigen Neurone und Neuropilstrukturen des Nucleus infundibularis und Nucleus ventromedialis eine grüngelbe Fluoreszenz (Methode von Falck und Owman). Der sog. Basiskern des Nucleus infundibularis zeichnet sich bei beiden Vogelarten durch eine wesentlich stärkere Fluoreszenzintensität aus als die beiden gleichmäßig leuchtenden dorsalen Auflagerungen. In der Eminentia mediana von Grünfink und Ente sind in einer subependymalen Zone feine fluoreszierende Granula zu beobachten. Die Palisadenschicht weist nur einen schwach leuchtenden Saum auf; lediglich bei zwei von 65 untersuchten Grünfinken ließ sich hier ein stärkerer Fluoreszenzstreifen darstellen. Die Fluoreszenzphänomene sind in der mit Paraldehydfuchsin elektiv färbbaren Pars anterior (rostralis) der Eminentia mediana stärker als in der Pars posterior (caudalis). Vom rostralen Abschnitt der Eminentia mediana und vom Nucleus infundibularis lassen sich fluoreszierende Faserzüge bis zur lateralen Zellgruppe des Nucleus supraopticus verfolgen; der Ursprung dieser Bahn ist unbekannt. Die nicht fluoreszierenden Perikaryen des Nucleus supraopticus sind in einen stark leuchtenden Faserfilz eingebettet. Die Ergebnisse der Reserpinbehandlung und der mikrospektrographischen Bestimmung (Maximum des Emissionsspektrums bei 485 nm) sprechen dafür, daß für die Fluoreszenz der kleinzelligen Tuberkerne Monoamine (Dopamin/ Noradrenalin) verantwortlich sind. Eine fluoreszenzmikroskopische Unterscheidung von Dopamin und Noradrenalin war im Zwischenhirn-Hypophysensystem von Carduelis chloris und Anas platyrhynchos bisher nicht möglich.

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Distribution of monoamine fluorophores in the hypothalamo-hypophysial system of Carduelis chloris and Anas platyrhynchos

Summary Neurons and neuropile structures of the infundibular and ventromedial nuclei of the hypothalami of the greenfinch (Carduelis chloris) and the mallard (Anas platyrhynchos) displayed a green-yellow fluorescence with the method of Falck and Owman. The fluorescence of the basal layer of the infundibular nucleus in both of these species is significantly stronger than that of the middle and dorsal layers of this nucleus. Fine fluorescent granules can be observed in a subependymal zone in the median eminence of both species. The palisade layer shows only a weakly fluorescent margin; only in two of 65 greenfinches investigated was it possible to demonstrate here a stronger fluorescent band. The fluorescence was stronger in the anterior median eminence, which is aldehydefuchsin positive, than in the posterior median eminence. From the anterior part of the median eminence and from the infundibular nucleus, it was possible to trace fluorescent fibers to the lateral cell groups of the supraoptic nucleus; the origin of this tract is unknown. The nonfluorescent perikarya of the supraoptic nucleus lie in a meshwork of fluorescent fibers. The results of treatment with reserpine and microspectrographic analysis (maximum emission at 485 nm) suggest that the fluorescence of the tuberal nuclei is attributable to monoamines (dopamine and norepinephrine). A differentiation of dopamine and epinephrine in the hypothalamo-hypophysial system of Carduelis chloris and Anas platyrhynchos has thus far not been possible by fluorescence microscopy.

Mit Unterstützung durch die Deutsche Forschungsgemeinschaft. Herrn Prof. D. S. Farner, Seattle, danke ich für freundliche Anteilnahme am Fortgang dieser Studien.     

Microspectrofluorometric identification of formaldehyde induced fluorescence in hypothalamic nuclei of Xenopus laevis tadpoles

Summary To identify the monoamine (s) produced in the paraventricular organ (PVO) and the nucleus infundibularis dorsalis (NID) of Xenopus laevis tadpoles, formaldehyde-induced fluorescence in these hypothalamic structures was analysed by microspectrofluorometric techniques. Reference values were obtained by recording excitation and emission spectra of fluorescence in monoamine containing protein models. The maxima of the excitation and emission spectra, both under normal conditions and after treatment with HCl vapour, indicate the presence of dopamine. Based on a number of emission spectra, the PVO and NID might also contain serotonin. With regard to the functional significance of dopamine produced in the hypothalamic nuclei, it may be concluded that the catecholamine is probably identical with the melanotropin inhibiting factor (MIF).The authors wish to thank Prof. Dr. P.G.W.J. van Oordt for his stimulating interest and support. The skillful assistance and valuable contributions of Miss A. G. Fennema and Miss M.G.A. de Bruyn are gratefully acknowledged. Many thanks are due to Prof. Dr. A. Oksche for the opportunity of performing measurements on fluorescence, during a visit to his institute (Zentrum für Anatomie und Cytobiologie, Gießen, BRD). The measurements were carried out by Dr. H.-G. Hartwig, whose help and advice are highly appreciated.     

Influence of thyroid hormone on the development of preoptic-hypothalamic monoaminergic neurons in tadpoles of Bufo bufo japonicus

The effect of thyroid hormone on the development of diencephalic monoaminergic neurons was studied in tadpoles of Bufo bufo japonicus. Monoamine-containing neurons in the preoptic recess organ (PRO) appeared later than those in the paraventricular organ (PVO) and nucleus infundibularis dorsalis (NID). After deprivation of thyroidal primordium no fluorescent neurons developed in the PRO. Development of monoaminergic neurons in the PVO and NID was not affected by thyroidectomy. Thyroxine treatment brought about the fluorescent neurons in the PRO of the thyroidectomized tadpoles. Fluorescent terminals in the median eminence became conspicuous around the capillaries which penetrated to the median emience, when the tadpoles reached late prometamorphic stage. In the median eminence of thyroidectomized tadpoles, the monoaminergic axon terminals did not develop. Thyroxine induced both the fluorescent terminals and the capillary penetration in the median eminence of the thyroidectomized tadpoles. In the tadpoles hypophysectomized at tail-bud stage, thyroxine induced neither the fluorescent terminals nor the capillaries in the median eminence.     

The organization of serotonin-immunoreactive neuronal systems in the brain of the crested newt,Triturus cristatus carnifex Laur.

Summary The distribution of serotonin (5-HT) immunoreactive structures has been investigated in the brain of the crested newt by means of indirect immunofluorescence, and unlabeled antibody peroxidase-antiperoxidase-complex (PAP) or biotin-avidin-system (BAS) techniques. In the newt, the bulk of the serotoninergic system extends from the raphe region of the medulla oblongata, through the isthmus, toward the mesencephalic tegmentum, and is characterized by pyriform neurons mainly located in a subependymal position, close to the midline. Also in the caudal hypothalamus, in addition to some 5-HT-positive adenohypophysial cells, many immunoreactive CSF-contacting neurons are found lining the paraventricular organ and the nucleus infundibularis dorsalis. A rich serotoninergic innervation was observed in the preoptic area and in the habenular complex. Concerning the telencephalon, immunopositive nerve fibers are encountered in the dorsal pallium, primordium hippocampi, striatum and olfactory bulbs. The general organization of serotoninergic systems in the newt brain exhibit close similarities to that described in higher vertebrates.     

1例雄性朱鹮脑内脑啡肽的免疫组织化学分布

用免疫组织化学方法研究脑啡肽(ENK)在极危物种朱(Nipponia nippon)脑内的分布,结合计算机图像分析仪检测免疫阳性细胞和末梢的灰度值。ENK阳性细胞、纤维和终末分布如下:发声核团有原纹状体中间区腹部、丘脑背内侧核外侧部、中脑丘间核、中脑背内侧核、延髓舌下神经核。听觉中枢有丘脑卵圆核壳区、中脑背外侧核壳区、脑桥外侧丘系腹核、上橄榄核、耳蜗核等。内分泌核团有视前区前核、旧纹状体增加部、下丘脑外侧核、下丘脑腹内侧核等。结果表明,朱脑内ENK可能对发声、听觉和下丘脑内分泌的生理活动有一定的调制作用。     

Retinal projections in the Northern Water snake Natrix sipedon sipedon (L.)

Retinal projections were studied experimentally in the Northern water snake using modifications of the Nauta silver impregnation technique. Contralaterally, the retina projects to nucleus geniculatus lateralis pars dorsalis and pars ventralis, nucleus lentiformis mesencephali and nucleus geniculatus pretectalis. A sparse projection was also observed to nucleus ovalis. An additional afferent thalamic projection to nucleus ventrolateralis was found in two cases. The retina projects ipsilaterally to the dorsolateral portion of nucleus geniculatus lateralis pars dorsalis, and sparsely to nucleus lentiformis mesencephali and nucleus geniculatus pretectalis. Nucleus posterodorsalis receives dense bilateral retinal projections. Contralaterally, the retina also projects to the superficial layers of the tectum (layers 8–13 of Ramón) and to nucleus opticus tegmenti. Armstrong's findings that the retinal projections in Natrix are qualittatively similar to those in lizards were confirmed. However there are marked quantitative differences among the various pathways and their corresponding nuclei. These differences are particularly striking in comparing the visual projections to the dorsal thalamus, the retino-tecto-rotundal and the retino-geniculate systems. The first is reduced in volume and the second is markedly increased in volume in comparison with lizards. These data lend support to the theories of Walls that snakes evolved from fossorial lizards and of Underwood that the eyes of these lizards underwent reduction but not complete degeneration. Qualitatively the retinal projections are conservative among lizards and snakes, but a history of reduction of these pathways in ancestral snakes with a selective increase in the retino-geniculate system as a surface niche was reattained is reflected in the anatomy of this ophidian visual system.     

Comparative myology of the mandibular and hyoid arches of sharks of the order hexanchiformes and their bearing on its monophyly and phylogenetic relationships (Chondrichthyes: Elasmobranchii)

The order Hexanchiformes currently comprises two families, Chlamydoselachidae (frilled sharks) and Hexanchidae (six‐ and seven‐gill sharks), but its monophyly and relationships with other elasmobranchs are still discussed. Previous studies of hexanchiforms addressing these issues were based mainly on external morphology, teeth, skeletal features, and molecular data, whereas the employment of characters derived from variations in muscles has not been significantly explored. Dissections of four species of Hexanchiformes (including Chlamydoselachus anguineus) are reported here describing the mandibular (musculus adductor mandibulae dorsalis, m. adductor mandibulae ventralis, m. levator labii superioris, m. intermandibularis, and m. constrictor dorsalis) and hyoidean (m. constrictor hyoideus dorsalis and ventralis) arch muscles. Our results provide new data concerning the relationships of hexanchiforms to other elasmobranchs. The m. adductor mandibulae superficialis is described and illustrated in C. anguineus, contradicting previous accounts in which is was considered absent. The anteroposterior orientation of the m. adductor mandibulae superficialis in Chlamydoselachus is similar to the pattern found in hexanchids, squaloids, and hypnosqualeans (including batoids), suggesting it was secondarily lost in Echinorhinus. This muscle therefore provides further support for the inclusion of the Chlamydoselachidae and Hexanchidae in the Squalomorphi, and not basal to all other elasmobranchs or nested within an all‐shark collective, as has been previously proposed. However, the m. adductor mandibulae superficialis originating at the jaw joint and with an aponeurotic insertion in hexanchids, squaliforms, and hypnosqualeans, may be a separate derived feature uniting these taxa. The insertion of the m. constrictor dorsalis is restricted to the postorbital articulation in hexanchids, whereas it extends farther anteriorly in C. anguineus. The insertion of the m. constrictor hyoideus dorsalis solely on the palatoquadrate is found exclusively in the Hexanchidae. We conclude that no specific pattern of mandibular or hyoid arch muscles support the monophyly of hexanchiforms (i.e., including Chlamydoselachus). J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

Localization of binding sites for atrial natriuretic factor and angiotensin II in the central nervous system of the clawed toad Xenopus laevis

Summary The distribution of binding sites for atrial natriuretic factor (ANF) and angiotensin II (A II) was investigated in the central nervous system (CNS) of the clawed toad Xenopus laevis by means of in vitro autoradiography using [¹²⁵I]-rat ANF(99–126) or [¹²⁵I] [Val⁵] A II and [¹²⁵I]human A II as labeled ligands. The highest densities of specific ANF-binding were detected in the nucleus habenularis, thalamic regions, hypophyseal pars nervosa and nucleus interpeduncularis. Moderate ANF-binding was found in the bulbus olfactorius, pallium, septum, striatum, lateral forebrain bundle, nucleus infundibularis, hypophyseal pars distalis and tectum. The highest levels of specific A II binding sites were observed in the nucleus praeopticus, nucleus habenularis, hypophyseal pars nervosa and pars distalis, whereas the amygdala contained moderate A II binding. The existence of specific binding sites for ANF and A II in the CNS of Xenopus laevis suggests that both peptides act as neurotransmitters or neuromodulators in the amphibian CNS. The co-localization of dense binding sites for both peptides in the nucleus habenularis, hypophyseal pars nervosa and pars distalis supports the view that ANF and A II have opposite regulatory functions in these regions.     

Coding of sound location and frequency in the auditory midbrain of diurnal birds of prey,families accipitridae and falconidae

Summary The coding of sound frequency and location in the avian auditory midbrain nucleus (nMLD) was examined in three diurnal raptors: the brown falcon (Falco berigora), the swamp harrier (Circus aeruginosus) and the brown goshawk (Accipiter fasciatus). Previously this nucleus has been studied with free field stimuli in only one other species, the barn owl (Tyto alba).We found some parallels between the organisation of nMLD in the diurnal raptors and that reported in the barn owl in that the central region of nMLD was tonotopically organised and contained cells that did not encode location, and the lateral region (nMLDl) contained cells which were sensitive to stimulus position. However, unlike the barn owl, which has units with circumscribed receptive fields, cells sensitive to stimulus location had large receptive fields which were restricted in azimuth but not in elevation (hemifield units). Such cells could not provide an acoustic space map in which both azimuthal and elevational dimensions were represented, but there was a tendency for units with contralateral borders to be found superficially, and those with ipsilateral borders to be found deep, in nMLDl. Hemifield units displayed receptive field properties consistent with the directional properties of the tympana in the presence of sound transmission through the interaural canal, if there is a central mechanism which is sensitive to interaural intensity differences.Abbreviations nMLD nucleus mesencephalicus lateralis pars dorsalis - SPL sound pressure level re 20 Pa - nMLDl lateral region of nMLD - ICC central nucleus of the inferior colliculus - ICX external nucleus of the inferior colliculus - IID interaural intensity difference - EI excitatory inhibitory