Serotonin-like immunoreactivity in the central nervous system and gonad of the scallop,Patinopecten yessoensis

Summary The localization of neurons containing serotonin in the central nervous system and the gonad of the scallop, Patinopecten yessoensis, was examined immunohistochemically. In the central nervous system a large number of immunoreactive perikarya were observed in the following regions: a part of the anterior lobe of the cerebral ganglion; the posterior lobe of the cerebral ganglion; the pedal ganglion; and the accessory ganglion. No immunoreactive perikarya were found in the visceral ganglion. Numerous immunoreactive fibers were revealed in the neuropil of all central ganglia. In the gonadal region immunoreactive fibers were distributed around the gonoduct and along the germinal epithelium.This work was supported by a grant from the Ministry of Education, Science and Culture, Japan     

Serotonin immunoreactivity of neurons in the gastropod Aplysia californica

Serotonergic neurons and axons were mapped in the central ganglia of Aplysia californica using antiserotonin antibody on intact ganglia and on serial sections. Immunoreactive axons and processes were present in all ganglia and nerves, and distinct somata were detected in all ganglia except the buccal and pleural ganglia. The cells stained included known serotonergic neurons: the giant cerebral neurons and the RB cells of the abdominal ganglion. The area of the abdominal ganglion where interneurons are located which produce facilitation during the gill withdrawal reflex was carefully examined for antiserotonin immunoreactive neurons. None were found, but two bilaterally symmetric pairs of immunoreactive axons were identified which descend from the contralateral cerebral or pedal ganglion to abdominal ganglion. Because of the continuous proximity of this pair of axons, they could be recognized and traced into the abdominal ganglion neuropil in each preparation. If serotonin is a facilitating transmitter in the abdominal ganglion, these and other antiserotonin immunoreactive axons in the pleuroabdominal connectives may be implicated in this facilitation.     

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。     

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.     

Distribution of GABA-like immunoreactive neurons in the slug Limax maximus

Summary Immunohistochemical techniques were used to study the distribution of gamma-amino butyric acid (GABA)-like immunoreactive neurons in the nervous system of the slug Limax maximus. Approximately 170 GABA-like immunoreactive cell bodies were found in the central nervous system. These were located in the cerebral, buccal and pedal ganglia. Most GABA-like immunoreactive neurons had small cell bodies, which were aggregated into discrete clusters within the cerebral and pedal ganglia. Three pairs of longer, uniquely identifiable, GABA-like immunoreactive cells were found in the cerebral ganglion. GABA-like immunoreactive nerve fibres were also found in all of the central ganglia but were absent from peripheral nerves. These results suggest that GABA acts as a central neurotransmitter in the slug. The possible roles of GABA-ergic neurotransmission in the slug are discussed.     

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。     

Distribution of serotonin-containing neurons in the central nervous system of the snail Helix pomatia

Summary The distribution of serotonin (5HT)-containing neurons in the central nervous system of the snail Helix pomatia has been determined in whole-mount preparations by use of immunocytochemical and in vivo 5,6-dihydroxy-tryptamine labelling. 5HT-immunoreactive neuronal somata occur in all but the buccal and pleural ganglia. Immunoreactive fibres are present throughout the central nervous system. The 5HT-immunoreactive neuronal somata characteristically appear in groups, located mainly in the cerebral, pedal, visceral and right parietal ganglia. The majority of 5HT-immunoreactive neurons is located in the pedal ganglia. Additionally a dense network of 5HT-immunoreactive varicose fibres is found in the neural sheath of the central nervous system including all the nerves and ganglia. The number and distribution of 5HT-immunoreactive neurons correlates with that demonstrated by 5,6-dihydroxytryptamine labelling method.     

Distribution of biogenic amines in the slug,Limax maximus

Summary The distribution of monoamines inLimax maximus was studied by the histochemical fluorescent method of Falck and Hillarp. The number of 5-HT-containing and catecholamine-containing perikarya in the central nervous system is small compared with the non-fluorescent perikarya. However, all the ganglia except the proto-cerebral ganglia have some amine-containing neurons. There are relatively larger numbers of fluorescent cells in the cerebral, visceral, pedal and right parietal ganglia than in the other ganglia. A single, giant 5-HT-containing neuron was observed in each meta-cerebral ganglion.Monoamine neurons are localised in a number of peripheral tissues (heart, integument, tentacles, penis retractor muscle, sole of foot, kidney, alimentary canal, reproductive organs and tentacular, pharyngeal and cephalic retractor muscles). Neurons containing catecholamine are mostly associated with sensory structures such as the statocysts, the retina of the eye and the integument of the tentacles, whereas 5-HT-containing nerve fibres are mainly observed in muscle tissues.We wish to thank the Wellcome Trust for financial support.     

Observations of serotonin and FMRFamide-like immunoreactivity in palp sensory structures and the anterior nervous system of spionid polychaetes

Evidence suggests that ciliated sensory structures on the feeding palps of spionid polychaetes may function as chemoreceptors to modulate deposit-feeding activity. To investigate the probable sensory nature of these ciliated cells, we used immunohistochemistry, epi-fluorescence, and confocal laser scanning microscopy to label and image sensory cells, nerves, and their organization relative to the anterior central nervous system in several spionid polychaete species. Antibodies directed against acetylated alphatubulin were used to label the nervous system and detail the innervation of palp sensory cells in all species. In addition, the distribution of serotonin (5-HT) and FMRFamide-like immunoreactivity was compared in the spionid polychaetes Dipolydora quadrilobata and Pygospio elegans. The distribution of serotonin immunoreactivity was also examined in the palps of Polydora cornuta and Streblospio benedicti. Serotonin immunoreactivity was concentrated in cells underlying the food groove of the palps, in the palp nerves, and in the cerebral ganglion. FMRFamide-like immunoreactivity was associated with the cerebral ganglia, nuchal organs and palp nerves, and also with the perikarya of ciliated sensory cells on the palps.     

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.     

Comparative distribution of urocortin- and CRF-like immunoreactivities in the nervous system of the earthworm Lumbricus terrestris

Corticotropin-releasing factor (CRF) and urocortin (Ucn) are both members of the CRF neuropeptide family. The distribution of Ucn- and CRF-like immunoreactive (ir) structures in the central nervous system of several vertebrate species has been studied, but little is known about that in non-vertebrates. We used a highly specific polyclonal antibody against rat Ucn and CRF to determine and compare the distribution of Ucn- and CRF-like immunoreactivity in the earthworm nervous system. Several Ucn- and CRF-like ir perikarya were described in the cerebral ganglion, subesophageal and ventral cord ganglia. The majority of Ucn-like ir cells were found in the ventral ganglia, whereas CRF-like ir cells were most abundant in the cerebral ganglion. Scattered Ucn- and CRF-like ir varicose fiber terminals were seen in all areas of the earthworm central nervous system. Ucn-like ir cell bodies and fiber terminals were also demonstrated in the pharyngeal wall. No co-localization of Ucn- and CRF-like ir nervous structures were observed. This study provided morphological evidence that Ucn- and CRF-like neurosecretory products exist in the earthworm central nervous system. Furthermore, both the distribution and morphology of Ucn- and CRF-like ir structures were distinct, therefore, it can be hypothesized that these neuropeptides exert different neurendocrine functions in the earthworm nervous system.     

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.     

Localization of pigment-dispersing hormone (PDH) immunoreactivity in the central nervous system of Carcinus maenas and Orconectes limosus (Crustacea), with reference to FMRFamide immunoreactivity in O. limosus

Summary By use of antisera raised against synthetic pigment-dispersing hormone (PDH) of Uca pugilator and FMRFamide, the distribution of immunoreactive structures in the central nervous system (CNS) of Carcinus maenas and Orconectes limosus was studied by light microscopy. In both species, a total of 10–12 PDH-positive perikarya occur amongst the anterior medial, dorsal lateral and angular somata of the cerebral ganglion (CG). In C. maenas, one PDH-perikaryon was found in each commissural ganglion (COG) and several more in the thoracic ganglion. In O. limosus, only four immunopositive perikarya could be demonstrated in the ventral nerve cord, i.e., two somata in the anterior and two in the posterior region of the suboesophageal ganglion (SOG). PDH-immunoreactive tracts and fiber plexuses were present in all central ganglia of both species, and individual axons were observed in the connectives. FMRFamide-immunoreactivity was studied in O. limosus only. Neurons of different morphological types were found throughout the entire CNS, including numerous perikarya in the anterior medial, anterior olfactory, dorsal lateral and posterior cell groups of the CG. Four perikarya were found in the COG, six large and numerous smaller ones in the SOG, and up to eight cells in each of the thoracic and abdominal ganglia. In each ganglion, the perikarya form fiber plexuses. Axons from neurons belonging to the CG could be traced into the ventral nerve cord; nerve fibers arising from perikarya in the SOG appeared to project to the posterior ganglia. In none of the structures examined colocalization of PDH- and FMRF-amide-immunoreactivity was observed.Dedicated to Prof. K.-E. Wohlfarth-Bottermann on the occasion of his 65th birthday     

Peptide B induction of bag-cell activity in Aplysia: localization of sites of action to the cerebral and pleural ganglia

The bag cells of the marine mollusc Aplysia are model neuroendocrine cells involved in the initiation of egg laying and its associated behaviors, but the natural stimulus triggering bag-cell activity is not known. The atrial gland of A. californica, an exocrine organ in the reproductive tract, contains two structurally related peptides (A and B) which can induce an afterdischarge in vitro, and these peptides can be used to probe the central nervous system for sites where extrinsic excitatory input onto the bag-cell system might occur. These sites were identified in a series of lesion and ablation experiments. The entire central nervous system was removed from an animal and placed in a chamber with two compartments which could be independently perfused, allowing peptides (atrial gland extract or purified peptide B) to be selectively applied to specific regions of the nervous system while bag-cell activity was monitored using extracellular suction electrodes. Afterdischarges were consistently and reliably induced when peptides were applied to the cerebral ganglion, the pleural ganglia, the cerebropleural connectives, or the rostral 10-15% of the pleurovisceral connectives, provided that an intact neuronal pathway connected the site of peptide application with the bag cells. In contrast, afterdischarges were never observed when peptides were selectively applied to the buccal or pedal ganglia and only rarely observed when applied to the abdominal ganglion and caudal pleurovisceral connectives. These results support the hypothesis that bag-cell processes and/or neuron(s) presynaptically excitatory to the bag cells are located in the pleural and cerebral ganglia and narrow the region of the central nervous system where the critical initiator element(s) can be identified.     

Localization of glutamate-like immunoreactive neurons in the central and peripheral nervous system of the adult and developing pond snail, Lymnaea stagnalis

We investigated the distribution and projection patterns of central and peripheral glutamate-like immunoreactive (GLU-LIR) neurons in the adult and developing nervous system of Lymnaea. Altogether, 50-60 GLU-LIR neurons are present in the adult central nervous system. GLU-LIR labeling is shown in the interganglionic bundle system and at the varicosities in neuropil of the central ganglia. In the periphery, the foot, lip, and tentacle contain numerous GLU-LIR bipolar sensory neurons. In the juvenile Lymnaea, GLU-LIR elements at the periphery display a pattern of distribution similar to that seen in adults, whereas labeled neurons increase in number in the different ganglia of the central nervous system from juvenile stage P1 up to adulthood. During embryogenesis, GLU-LIR innervation can be detected first at the 50% stage of embryonic development (the E50% stage) in the neuropil of the cerebral and pedal ganglia, followed by the emergence of labeled pedal nerve roots at the E75% stage. Before hatching, at the E90% stage, a few GLU-LIR sensory cells can be found in the caudal foot region. Our findings indicate a wide range of occurrence and a broad role for glutamate in the gastropod nervous system; hence they provide a basis for future studies on glutamatergic events in networks underlying different behaviors.     

Distribution and anatomy of GABA-like immunoreactive neurons in the central and peripheral nervous system of the snail Helix pomatia

Gamma-aminobutyric acid (GABA)-like immunoreactive neurons were studied in the central and peripheral nervous system of Helix pomatia by applying immunocytochemistry on whole-mount preparations and serial paraffin sections. GABA-immunoreactive cell bodies were found in the buccal, cerebral and pedal ganglia, but only GABA-immunoreactive fibers were found in the viscero-parietal-pleural ganglion complex. The majority of GABA-immunoreactive cell bodies were located in the pedal ganglia but a few could be found in the buccal ganglia. Varicose GABA-ir fibers could be seen in the neuropil areas and in distinct areas of the cell body layer of the ganglia. The majority of GABA-ir axonal processes run into the connectives and commissures of the ganglia, indicating an important central integrative role of GABA-immunoreactive neurons. GABA may also have a peripheral role, since GABA-immunoreactive fibers could be demonstrated in peripheral nerves and the lips. Glutamate injection did not change the number or distribution of GABA-immunoreactive neurons, but induced GABA immunoreactivity in elements of the connective tissue ensheathing the muscle cells and fibers of the buccal musculature. This shows that GABA may be present in different non-neural tissues as a product of general metabolic pathways.     

Hyalomma dromedarii (Acari: Ixodoidea: Ixodidae): Central and peripheral nervous system anatomy

TheHyalommadromedarii central nervous system, the synganglion, is an integrated nerve mass concentrated around the esophagus and formed by fusion of a small anterodorsal supraesophageal part an a large posteroventral subesophageal part. The supraesophageal part consists of the protocerebrum including a pair of optic ganglia, a pair of cheliceral ganglia, a pair of pedipalpal ganglia, and the stomodeal pons. The subesophageal part includes four paired pedal ganglia and the complex opisthosomatic ganglion. The peripheral nervous system includes the following pairs of nerves: optic, cheliceral, pedipalpal, primary and accessory (histologically traced); also unpaired pharyngeal and recurrent nerves, four pairs of pedal nerve trunks, each with a hemal branch, and two pairs of opisthosomatic nerves. Each peripheral nerve is traced distally to the innervation site. The salivary glands are innervated anteriorly by branches of the pedipalpal nerve and medially by branches of the hemal nerves associated with the third pedal nerves.Reprint request should be sent to: Medical Zoology Department, NAMRU-3, Fleet Post Office, New York 09527, U.S.A.     

Distribution of tyrosine-hydroxylase-immunoreactive and dopamine-immunoreactive neurons in the central nervous system of the snail Helix pomatia

The distribution and characterization of dopamine-containing neurons are described in the different ganglia of the central nervous system of Helix on the basis of the distribution of tyrosine hydroxylase immunoreactive (TH-ir) and dopamine immunoreactive (DA-ir) neurons. Both TH-ir and DA-ir cell bodies of small diameter (10–25 m) can be observed in the buccal, cerebral and pedal ganglia, dominantly on their ventral surface, and concentrated in small groups close to the origin of the peripheral nerves. The viscero-parietal-pleural ganglion complex is free of immunoreactive cell bodies but contains a dense fiber system. The largest number of TH-ir and DA-ir neurons can be detected in the pedal, and cerebral ganglia. The average number of TH-ir and DA-ir neurons significantly differs but all the identifiable groups of TH-ir neurons also show DA-immunoreactivity. Therefore, we consider the TH-ir neurons in those groups as being DA-containing neurons. The amounts of DA in the different ganglia assayed by high performance liquid chromatography correspond to the distribution and number of TH-ir and DA-ir neurons in the different ganglia. The axon processes of the labeled small-diameter neurons send thin proximal branches toward the cell body layer but only rarely surround cell bodics, whereas distally they give off numerous branches in the neuropil and then leave the ganglion through the peripheral nerves. In the cerebral ganglia, the analysis of the TH-ir pathways indicates that the largest groups of labeled neurons send their processes through the peripheral nerves in a topographic order. These results furnish morphological evidence that DA-containing neurons of Helix pomatia have both central and peripheral roles in neuronal regulation.     

Evidence that the Central Pattern Generator for Swimming in Tritonia Arose from a Non-Rhythmic Neuromodulatory Arousal System: Implications for the Evolution of Specialized Behavior

Comparisons of the nervous systems of closely related invertebratespecies show that identified neurons tend to be highly conservedeven though the behaviors in which they participate vary. Allopisthobranch molluscs examined have a similar set of serotonin-immunoreactiveneurons located medially in the cerebral ganglion. In a smallnumber of species, these neurons have been physiologically andmorphologically identified. In the nudibranch, Tritonia diomedea,three of the neurons (the dorsal swim interneurons, DSIs) havebeen shown to be members of the central pattern generator (CPG)underlying dorsal/ventral swimming. The DSIs act as intrinsicneuromodulators, altering cellular and synaptic properties withinthe swim CPG circuit. Putative homologues of the DSIs have beenidentified in a number of other opisthobranchs. In the notaspid,Pleurobranchaea californica, the apparent DSI homologues (As1–3)play a similar role in the escape swim and they also have widespreadactions on other systems such as feeding and ciliary locomotion.In the gymnosomatid, Clione limacina, the presumed homologousneurons (Cr-SP) are not part of the swimming pattern generator,which is located in the pedal ganglia, but act as extrinsicmodulators, responding to noxious stimuli and increasing thefrequency of the swim motor program. Putative homologous neuronsare also present in non-swimming species such as the anaspid,Aplysia californica, where at least one of the cerebral serotonergicneurons, CC3 (CB-1), evokes neuromodulatory actions in responseto noxious stimuli. Thus, the CPG circuit in Tritonia appearsto have evolved from the interconnections of neurons that arecommon to other opisthobranchs where they participate in arousalto noxious stimuli but are not rhythmically active.     

Locomotion in the pulmonate snail Melampus--II. Recovery after pedal ganglion excision

1. When one pedal ganglion is removed, snails first crawl using the unoperated side of the foot, but in 4-8 weeks the operated side exhibits an anterior-to-posterior gradient of recovery. 2. A ganglion bud bridges the site of the missing ganglion and axons project from intact central ganglia into the foot. 3. Rhythmic activity in right and left pedal nerve pairs is correlated during locomotion in the regenerated snails. 4. The oscillator in the remaining pedal ganglion drives bilaterally coordinated activity. Regenerated projections from the cerebral ganglia through the bud to the remaining pedal ganglion suffice to initiate locomotion.