On the serotonergic nervous system of two planktonic rotifers, Conochilus coenobasis and C. dossuarius (Monogononta, Flosculariacea, Conochilidae)

The serotonergic nervous systems of two non-colonial species of Conochilus were examined to obtain the first immunohistochemical insights into the neuroanatomy of species of Flosculariacea (Rotifera, Monogononta). Species of Conochilus, subgenus Conochiloides, were examined using serotonin (5-HT) immunohistochemistry, epifluorescence and confocal laser scanning microscopy, and 3D computer imaging software. In specimens of C. coenobasis and C. dossuarius, the serotonergic nervous system is defined by a dorsal cerebral ganglion, apically directed cerebral neurites, and paired nerve cords. The cerebral ganglion contains approximately four pairs of small 5-HT-immunoreactive perikarya; one pair innervates the posterior nerve cords and three pairs innervate the apical field. The most dorsal pair innervates a coronal nerve ring that encircles the apical field. Within the apical field is a second nerve ring that outlines the inner border of the coronal cilia. Together, both the inner and outer nerve rings may function to modulate ciliary activity of the corona. The other two pairs of perikarya innervate a region around the mouth. Specific differences in the distribution of serotonergic neurons between species of Conochilus and previously examined ploimate rotifers include the following: (a) a lack of immunoreactivity in the mastax; (b) a greater number of apically directed serotonergic neurites; and (c) a complete innervation of the corona in both species of Conochilus. These differences in nervous system immunohistochemistry are discussed in reference to the phylogeny of the Monogononta.     

Structure and metamorphic remodeling of the larval nervous system and musculature of Phoronis pallida (Phoronida)

The structure of the larval nervous system and the musculature of Phoronis pallida were studied, as well as the remodeling of these systems at metamorphosis. The serotonergic portion of the apical ganglion is a U-shaped field of cell bodies that send projections into a central neuropil. The majority of the serotonergic cells are (at least) bipolar sensory cells, and a few are nonsensory cells. Catecholaminergic cell bodies border the apical ganglion. The second (hood) sense organ develops at competence and is composed of bipolar sensory cells that send projections into a secondary neuropil. Musculature of the competent larva includes circular and longitudinal muscle fibers of the body wall, as well as elevators and depressors of the tentacles and hood. The juvenile nervous system and musculature are developed prior to metamorphosis and are integrated with those of the larva. Components of the juvenile nervous system include a diffuse neural net of serotonergic cell bodies and fibers and longitudinal catecholaminergic fibers. The juvenile body wall musculature consists of longitudinal fibers that overlie circular muscle fibers, except in the cincture regions, where this pattern is reversed. Metamorphosis is initiated by the larval neuromuscular system but is completed by the juvenile neuromuscular system. During metamorphosis, the larval nervous system and the musculature undergo cell death, and the larval tentacles and gut are remodeled into the juvenile arrangement. Although the phoronid nervous system has often been described as deuterostome-like, these data show that several cytological aspects of the larval and juvenile neuromuscular systems also have protostome (lophotrochozoan) characteristics.     

The neurotoxic effects of manganese on the dopaminergic innervation of the gill of the bivalve mollusc, Crassostrea virginica

We examined effects of manganese on the nervous system and innervation of lateral cilia of Crassostrea virginica. While essential in trace amounts, tissue manganese accumulation is neurotoxic, inducing Manganism, a Parkinson's-like disease in humans. Lateral cilia of the gill of C. virginica are controlled by a reciprocal serotonergic-dopaminergic innervation from their ganglia. Oysters were incubated 3 days in the presence of up to 1 mM manganese, followed by superfusion of the cerebral ganglia, visceral ganglia or gill with dopamine or serotonin. Beating rates of cilia were measured by stroboscopic microscopy of isolated gill preparations or gill preparations with the ipsilateral cerebral and/or visceral ganglia attached. Acute manganese treatments impaired the dopaminergic, cilio-inhibitory system, while having no effect on the serotonergic, cilio-excitatory system, which is in agreement with the proposed mechanism of manganese toxicity in humans. Manganese treatments also decreased endogenous dopamine levels in the cerebral and visceral ganglia, and gills, but not serotonin levels. We demonstrated that manganese disrupts the animal's dopaminergic system, and also that this preparation can be used to investigate mechanisms that underlie manganese neurotoxicity. It also may serve as a model in pharmacological studies of drugs to treat or prevent Manganism and other dopaminergic cell disorders.     

Monoamines and reproduction in Pecten maximus,a preliminary approach

Summary

The distribution of serotonin-like immunoreactivity was studied in the central nervous system and the gonad of Pecten maximus. Cerebral and pedal ganglia contain a well developed serotonin-immunoreactive neuronal subpopulation, whereas positive neurons are scarce in the visceral ganglion. The distribution pattern of immunoreactive elements in the gonad indicate that serotonin is involved in peripheral neurotransmission of this organ. Seasonal variations of monoamines (serotonin, dopamine and noradrenaline) have been investigated in the nervous system using HPLC. Lower concentrations of serotonin are observed during winter in the central nervous system; dopamine levels of the visceral ganglion are correlated to gonadal growth.     

Nervous network in larvae of the ascidian Ciona intestinalis

 With the use of the monoclonal antibody UA301, which specifically recognizes the nervous system in ascidian larvae, the neuronal connections of the peripheral and central nervous systems in the ascidian Ciona intestinalis were observed. Three types of peripheral nervous system neurons were found: two located in the larval trunk and the other in the larval tail. These neurons were epidermal and their axons extended to the central nervous system and connected with the visceral ganglion directly or indirectly. The most rostral system (rostral trunk epidermal neurons, RTEN) was distributed bilateral-symmetrically. In addition, presumptive papillar neurons in palps were found which might be related to the RTEN. Another neuron group (apical trunk epidermal neurons, ATEN) was located in the apical part of the trunk. The caudal peripheral nervous system (caudal epidermal neurons, CEN) was located at the dorsal and ventral midline of the caudal epidermis. In the larval central nervous system, two major axon bundles were observed: one was of a photoreceptor complex and the other was connected with RTEN. These axon bundles joined in the posterior sensory vesicle, ran posteriorly through the visceral ganglion and branched into two caudal nerves which ran along the lateral walls of the caudal nerve tube. In addition, some immunopositive cells existed in the most proximal part of the caudal nerve tube and may be motoneurons. Received: 8 September 1997 / Accepted: 14 December 1997     

First description of the serotonergic nervous system in a bdelloid rotifer: Macrotrachela quadricornifera Milne 1886 (Philodinidae)

Class Bdelloidea of phylum Rotifera comprises aquatic microinvertebrates that are known for both obligate parthenogenesis and for resisting desiccation through a dormant reversible state. In the frame of an investigation about the role of the nervous system in controlling life cycle, reproduction and dormancy, we describe the serotonergic system of a bdelloid, Macrotrachela quadricornifera, using serotonin immunohistochemistry and confocal laser scanning microscopy. Serotonin immunoreactivity is present in the cerebral ganglion, lateral nerve cords and peripheral neurites. The cerebral ganglion consists of perikarya that send neurites cephalically to the rostrum and corona. A pair of neurites exits the cerebral ganglion as lateral nerve cords, and proceeds caudally to the pedal ganglion where additional neurites enter the foot. Based on the location of serotonergic immunoreactivity, we hypothesize that the neurotransmitter is involved in both motor activity (e.g., ciliary beating, inchworm-like locomotion) and sensory activity. A comparison between the serotonergic nervous systems of M. quadricornifera and species of Monogononta reveals differences in the numbers and patterns of cerebral perikarya, peripheral perikarya, and periperhal neurites. These differences may have functional significance for understanding adaptations to specific environments and/or systematic significance for reconstructing the rotiferan ground pattern.     

Embryonic development and organogenesis in the snail Marisa cornuarietis (Mesogastropoda: Ampullariidae). V. Development of the nervous system.

The nervous system is ectodermal in origin. All nerve ganglia arise separately by proliferation and later delamination from the ectoderm, not by invagination. They become secondarily connected to one another by commissures and connectives developing as extensions from the peripheral layer of ganglionic nerve cells. Rudiments of the cerebral, pedal, pleural and intestinal (parietal) ganglia arise almost simultaneously at a relatively early stage (Stage V). The cerebral ganglia develop from the ectoderm of the head plates. Rudiments of the pedal and pleural ganglia are separate at their inception. They later fuse (Stage VI) to form a pleuro-pedal ganglionic mass on each side. The 2 intestinal ganglia are symmetrical at the beginning, but they soon lose their symmetry as a result of torsion. The right ganglion crosses to the left over the gut and persists as the supraintestinal ganglion. The left or subintestinal ganglion shifts to the right and forward, and fuses with the right pleural ganglion (Stage VIII), thus obscuring the chiastoneury. The paired buccal and single visceral (abdominal) ganglia start differentiating in Stage VII. The former develop from the ectodermal wall of the stomodaeum, while the visceral ganglion delaminates from the right wall of the visceral sac, then shifts to the left during torsion. The statocysts develop early (Stage V) from 2 ectodermal invaginations on either side of the rudimentary foot. They later separate from the overlying ectoderm and statoconi appear in their lumina. Contrary to earlier reports on related ampullariids, the osphradium proved to be ontogenetically older than the mantle and mantle cavity. It starts differentiating as a thickened ectodermal plate in the right wall of the visceral sac (Stage V). During torsion, it becomes engulfed in the mantle cavity and shifts to the left side, then is carried forward as the mantlegrow. The eyes develop late (Stage IX) as ectodermal invaginations which rapidly separate from the ectoderm to form closed vesicles. Their cells start differentiating before hatching to form the retina, in which pigment is deposited, and the inner cornea. The lens is secreted in the lumen of the eye and grows by addition of concentric layers of secretion.     

The development of the serotonergic and FMRF-amidergic nervous system in<Emphasis Type="Italic"> Antalis entalis</Emphasis> (Mollusca,Scaphopoda)

The morphogenesis of serotonin- and FMRF-amide-bearing neuronal elements in the scaphopod Antalis entalis was investigated by means of antibody staining and confocal laser scanning microscopy. Nervous system development starts with the establishment of two initial, flask-like, serotonergic central cells of the larval apical organ. Slightly later, the apical organ contains four serotonergic central cells which are interconnected with two lateral serotonergic cells via lateral nerve projections. At the same time the anlage of the adult FMRF-amide-positive cerebral nervous system starts at the base of the apical organ. Subsequently, the entire neuronal complex migrates behind the prototroch and the six larval serotonergic cells lose transmitter expression prior to metamorphic competence. There are no strictly larval FMRF-amide-positive neuronal structures. The development of major adult FMRF-amide-containing components such as the cerebral system, the visceral loop, and the buccal nerve cords, however, starts before the onset of metamorphosis. The anlage of the putative cerebral system is the only site of adult serotonin expression in Antalis larvae. Establishment of the adult FMRF-amidergic and serotonergic neuronal bauplan proceeds rapidly after metamorphosis. Neurogenesis reflects the general observation that the larval phase and the expression of distinct larval morphological features are less pronounced in Scaphopoda than in Gastropoda or Bivalvia. The degeneration of the entire larval apical organ before metamorphic competence argues against an involvement of this sensory system in scaphopod metamorphosis. The lack of data on the neurogenesis in the aplacophoran taxa prevent a final conclusion regarding the plesiomorphic condition in the Mollusca. Nevertheless, the results presented herein shed doubts on general theories regarding possible functions of larval "apical organs" of Lophotrochozoa or even Metazoa.     

Role of the giant serotonin-containing cell of the cerebral ganglion in the edible snail in organizing its food-acquiring behavior

By adding dopamine or serotonin to a bath with snail's isolated nervous system and by intracellular activation of giant cerebral serotonergic cells it was established in neurophysiological experiments that, in spite of activating effect of serotonin on buccal motorneurones, dopamine is the transmitter triggering feeding movements of the buccal mass and feeding pattern in buccal motorneurones. This conclusion is confirmed by behavioural experiments in which an experimental group was injected by neruotoxin 5,6-dihydroxytryptamine selectively impairing serotonergic neurones. The consumatory phase of feeding (triggered by dopamine) did not change in treated animals, while the appetitive phase was significantly impaired. It was noted that the giant metacerebral cell was activated during burst activity in buccal motoneurones. The conclusion is made that giant serotonergic cerebral cells only modulate but do not trigger the feeding behaviour in the snail Helix lucorum.     

Localization of a SALMFamide Neuropeptide in the Larval Nervous System of the Sand Dollar Dendraster excentricus

Using immunocytochemical methods we describe the localization of serotonin and the SALMFamide peptide, S1 (GFNSALMFamide), during embryonic and larval development of the echinoid Dendraster excentricus. Anti-SI immunoreactivity first appears in the apical ganglion in late gastrulae at the same time as anti-serotonin immunoreactivity. Initially, anti-S1 immunoreactivity is restricted to fibres of the neuropile, but in later feeding stages, cell bodies are also immunoreactive. Anti-S1 immunoreactivity appears as 2–4 cells in the oral ganglion of early prism stage larvae, whereas anti-serotonin immunoreactivity does not occur in the oral ganglion until the 8-arm stage. Anti-S1 immunoreactivity also occurs in diffuse fibres in the oesophagus and in a single fibre encircling the pyloric sphincter of the gut. A reticular network associated with the apical surface of the epithelial cells of the vestibule of the adult rudiment was anti-S1 immunoreactive. In double-labelling experiments, anti-serotonin and anti-S1 immunoreactivity co-localize in the neuropile of the apical ganglion. The distribution of S1, in association with putative sensory cells in the apical and oral ganglia and with muscles of the oesophagus and gut, suggests S1 may have diverse functions in the larval nervous system. The distribution of anti-S1 immunoreactivity in echinoid embryos and larvae supports the proposal that SALMFamide-like peptides are widely shared in echinoderms and potentially have a fundamental role in neural function.     

Initial analysis of immunochemical cell surface properties, location and formation of the serotonergic apical ganglion in sea urchin embryos

In the present study it was found that serotonergic apical ganglion (SAG)-forming cells in plutei of the sea urchin, Hemicentrotus pulcherrimus, possessed a characteristic pear shape with broad apical sides and a pointed basal side in the acron epithelium. The basal side extended axons through the space between the epithelium and the basal lamina toward the midline of the embryo that aligned parallel to the embryonic anteroposterior axis. Serotonergic apical ganglion-forming cells had epithelial cell surface-specific proteins on their entire surface. The SAG in 4-arm plutei was composed of a 4-cell trunk region that aligned at right angles to the embryonic anteroposterior axis, and forked into two branches of one to two cells at both ends. Two branches extended toward the oral and the other two toward the aboral region, respectively. Double-stained immunohistochemistry using antiserotonin antibodies and oral ectoderm-specific anti-Ecto V monoclonal antibody or aboral ectoderm-specific anti-Ars antibodies indicated that SAG was in the aboral ectoderm region. Serotonergic apical ganglion cells were first detected in late gastrulae and increased in number rapidly between 36 and 48 h after fertilization, and then slowly afterwards. A 5-bromo-2-deoxyuridine incorporation study indicated that none of the increased SAG cells were in the S phase during the aforementioned period, suggesting that SAG cells do not proliferate by cell division, but acquire the property in particular cells by transdifferentiation using a mechanism that has yet to be elucidated.     

扁玉螺中枢神经系统解剖及显微结构观察

对扁玉螺(Neverita didyma)中枢神经系统的大体解剖和显微结构进行了初步研究。结果表明,扁玉螺中枢神经系统包括一对口球神经节、一对脑神经节、一对侧神经节、一对足神经节及一个脏神经节。各神经节均由神经节被膜、胞体区及中央纤维网三部分组成。左右脑神经节之间和左右足神经节之间的联合以及脑-侧、脑-足和侧-足神经节之间的连索均较短。足神经节有明显的分区现象。     

Topology of the nervous system of Notommata copeus (Rotifera: Monogononta) revealed with anti-FMRFamide, -SCPb, and -serotonin (5-HT) immunohistochemistry

Abstract. The nervous system of the benthic freshwater rotifer, Notommata copeus , was examined using antibody probes, epifluorescence and confocal laser scanning microscopy, and digital imaging to highlight similarities with other monogonont rotifers. Immunoreactivity to anti-FMRFamide (Phe–Met–Arg–Phe–NH₂), -SCPb (small cardioactive peptide b), and -serotonin (5-HT, 5-hydroxytryptamine) was present in the central, peripheral, and stomatogastric nervous system. Specifically, anti-FMRFamide and -SCPb staining was abundant in perikarya and neurites of the cerebral ganglion, ventrolateral nerve cords, and mastax. In addition, a single loop-like neurite was present in between the nerve cords at the posterior end of the body. Serotonergic neurites were also abundant, and highlighted several cerebral pathways that included connections to the nerve cords and possibly the mastax. Novel neural pathways were also present in the posterior trunk region, where serotonergic neurites innervated the foot and lateral body wall. The results presented herein also highlight the utility of 3D visualization software to gain further insights into the organization and architecture of the rotifer cerebral ganglion.     

Hypothalamic 5-HT functional regulation through 5-HT1A and 5-HT2C receptors during pancreatic regeneration

5-HT receptors are predominantly located in the brain and are involved in pancreatic function and cell proliferation through sympathetic nervous system. The objective of this study was to investigate the role of hypothalamic 5-HT, 5-HT1A and 5-HT2C receptor binding and gene expression in rat model of pancreatic regeneration using 60% pancreatectomy. The pancreatic regeneration was evaluated by 5-HT content, 5-HT1A and 5-HT2C receptor gene expression in the hypothalamus of sham operated, 72 h and 7 days pancreatectomised rats. 5-HT content was quantified by HPLC. 5-HT1A receptor assay was done by using specific agonist [3H]8-OH DPAT. 5-HT2C receptor assay was done by using specific antagonist [3H]mesulergine. The expression of 5-HT1A and 5-HT2C receptor gene was analyzed by RT-PCR. 5-HT content was higher in the hypothalamus of 72 h pancreatectomised rats. 5-HT1A and 5-HT2C receptors were down-regulated in the hypothalamus. RT-PCR analysis revealed decreased 5-HT1A and 5-HT2C receptor mRNA expression. The 5-HT1A and 5-HT2C receptors gene expression in the 7 days pancreatectomised rats reversed to near sham level. This study is the first to identify 5-HT1A and 5-HT2C receptor gene expression in the hypothalamus during pancreatic regeneration in rats. Our results suggest the hypothalamic serotonergic receptor functional regulation during pancreatic regeneration.     

Aminergic cellular organization in the gills of Aplysia species

The constituent elements of the gills of Aplysia kurodai and A. juliana were examined for the presence of biogenic amines using histochemical, immunocytochemical, and HPLC techniques. Aminergic elements were revealed by glyoxylic acid-induced fluorescence in the branchial nerve, branchial ganglion, branchial vessels, and pinnules in both species. Three types of fluorescent cells were found in the neural plexus of the gill in each species. Two of them might be sensory neurons. Although HPLC analysis showed the presence of serotonin and dopamine in all gill structures including fluorescent neural elements, there were regional differences in concentrations of the monoamines. It was noted in the pinnules that there was a much higher concentration of dopamine than serotonin. Serotonin immunocytochemistry revealed neural processes which were immunoreactive to antiserotonin antibody, but serotonin immunoreactivity could not be found in a population of branchioganglionic neuron (BGN) somata. Serotonergic elements in the ganglion may be processes of the central ganglion, while dopaminergic elements may be processes of neurons in the neural plexus, located beyond the branchial ganglion. BGNs were activated by bath-applied dopamine and serotonin. These results suggest that dopaminergic sensory inputs from the neural plexus and serotonergic descending inputs from the abdominal ganglion may be among the inputs received by BGNs. It was found that serotonin depressed excitatory junctional potentials in muscle cells of the efferent branchial vessel, which were induced by an identified neuron of the abdominal ganglion. The aminergic cellular organization of the gill may involve serotonergic presynaptic-inhibitory fibers arising from the abdominal ganglion.     

Immunochemical study of galanin in the cat digestive tract and autonomic ganglia

The presence of galanin was examined in the cat gut and related autonomic nervous structures using radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). In the gut wall, the concentration of galanin-like immunoreactivity (GAL-LI) was assayed separately in the muscular layers with the nervous plexuses and in the mucosa and ranged from 0.35 to 0.55 pmol/g wet tissue. In the autonomic nervous structures, GAL-LI concentrations ranged from 0.22 (thoracic spinal ganglia) to 0.81 (inferior mesenteric ganglion) pmol/g wet tissue. The presence of galanin was checked by HPLC in the antrum, intestine, and colon. HPLC of extractable material revealed a major peak coeluting with the synthetic porcine peptide and minor earlier peaks representing likely different molecular forms of galanin. Our study strengthens the notion that galanin acts in nervous control of the cat gut functions.     

两种软体动物神经系统一氧化氮合酶的组织化学定位

运用一氧化氮合酶(NOS)组织化学方法研究了软体动物门双壳纲种类中国蛤蜊和腹足纲种类嫁Qi神经系统中NOS阳性细胞以及阳性纤维的分布。结果表明：在蛤蜊脑神经节腹内侧,每侧约有10-15个细胞呈强NOS阳性反应,其突起也呈强阳性反应,并经脑足神经节进入足神经节的中央纤维网中;足神经节内只有2个细胞呈弱阳性反应,其突起较短,进入足神经节中央纤维网中,但足神经节中,来自脑神经节阳性细胞和外周神经系统的纤维大多呈NOS阳性反应;脏神经节的前内侧部和后外侧部各有一个阳性细胞团,其突起分别进入后闭壳肌水管后外套膜神经和脑脏神经索。脏神经节背侧小细胞层以及联系两侧小细胞层的纤维也呈NOS阳性反应。嫁Qi中枢神经系统各神经节中没有发现NOS阳性胞体存在;脑神经节、足神经节、侧神经节以及脑—侧、脑—足、侧—脏连索中均有反应程度不同的NOS阳性纤维,这些纤维均源于外周神经。与已研究的软体动物比较,嫁Qi和前鳃亚纲其它种类一样,神经系统中NO作为信息分子可能主要存在于感觉神经。而中国蛤蜊的神经系统中一氧化氮作为信息分子则可能参与更广泛的神经调节过程。     

The aminergic control of cockroach salivary glands

The acinar salivary glands of cockroaches receive a dual innervation from the subesophageal ganglion and the stomatogastric nervous system. Acinar cells are surrounded by a plexus of dopaminergic and serotonergic varicose fibers. In addition, serotonergic terminals lie deep in the extracellular spaces between acinar cells. Excitation-secretion coupling in cockroach salivary glands is stimulated by both dopamine and serotonin. These monoamines cause increases in the intracellular concentrations of cAMP and Ca(2+). Stimulation of the glands by serotonin results in the production of a protein-rich saliva, whereas stimulation by dopamine results in saliva that is protein-free. Thus, two elementary secretory processes, namely electrolyte/water secretion and protein secretion, are triggered by different aminergic transmitters. Because of its simplicity and experimental accessibility, cockroach salivary glands have been used extensively as a model system to study the cellular actions of biogenic amines and to examine the pharmacological properties of biogenic amine receptors. In this review, we summarize current knowledge concerning the aminergic control of cockroach salivary glands and discuss our efforts to characterize Periplaneta biogenic amine receptors molecularly.