Mapping sensory nerve communications between peripheral nerve territories.

The human cutaneous sensory map has been a work in progress over the past century, depicting sensory territories supplied by both the spinal and cranial nerves. Two critical discoveries, which shaped our understanding of cutaneous innervation, were sensory dermatome overlap between contiguous spinal levels and axial lines across areas where no sensory overlap exists. These concepts define current dermatome maps. We wondered whether the overlap between contiguous sensory territories was even tighter: if neural communications were present in the peripheral nerve territories consistently connecting contiguous spinal levels? A literature search using peer-reviewed articles and established anatomy texts was performed aimed at identifying the presence of communications between sensory nerves in peripheral nerve territories and their relationship to areas of adjacent and non-adjacent spinal or cranial nerves and axial lines (lines of discontinuity) in the upper and lower limbs, trunk and perineum, and head and neck regions. Our findings demonstrate the consistent presence of sensory nerve communications between peripheral nerve territories derived from spinal nerves within areas of axial lines in the upper and lower limbs, trunk and perineum, and head and neck. We did not find examples of communications crossing axial lines in the limbs or lines of discontinuity in the face, but did find examples crossing axial lines in the trunk and perineum. Sensory nerve communications are common. They unify concepts of cutaneous innervation territories and their boundaries, and refine our understanding of the sensory map of the human skin.

Recurrent facial taste neurons of sea catfish Plotosus japonicus: morphology and organization in the ganglion.

This study investigated the morphology of the recurrent facial taste neurons and their organization in the recurrent ganglion of the sea catfish Plotosus japonicus. The recurrent ganglion is independent of the anterior ganglion, which consists of trigeminal, facial and anterior lateral line neurons that send peripheral fibres to the head region. The recurrent taste neurons are round or oval and bipolar, with thick peripheral and thin central fibres, and completely wrapped by membranous layers of satellite cells. Two peripheral nerve branches coursing to the trunk or pectoral fin originate from the recurrent ganglion. The results presented here show that the trunk and pectoral-fin neurons are independently distributed to form various sizes of groups, and the groups are intermingled throughout the ganglion. No distinct topographical relationship of the two nerve branches occurs in the ganglion. Centrally, the trunk and pectoral-fin branches project somatotopically in the anterolateral and intermediate medial regions of the trunk tail lobule of the facial lobe, respectively.

The independent evolution of the enlargement of the principal sensory nucleus of the trigeminal nerve in three different groups of birds.

In vertebrates, sensory specializations are usually correlated with increases in the brain areas associated with that specialization. This correlation is called the 'principle of proper mass' whereby the size of a neural structure is a reflection of the complexity of the behavior that it subserves. In recent years, several comparative studies have revealed examples of this principle in the visual and auditory system of birds, but somatosensory specializations have largely been ignored. Many species rely heavily on tactile information during feeding. Input from the beak, tongue and face, conveyed via the trigeminal, facial, glossopharyngeal and hypoglossal nerves, is first processed in the brain by the principal sensory nucleus of the trigeminal nerve (PrV) in the brainstem. Previous studies report that PrV is enlarged in some species that rely heavily on tactile input when feeding, but no extensive comparative studies have been performed. In this study, we assessed the volume of PrV in 73 species of birds to present a detailed analysis of the relative size variation of PrV using both conventional and phylogenetically based statistics. Overall, our results indicate that three distinct groups of birds have a hypertrophied PrV: waterfowl (Anseriformes), beak-probing shorebirds (Charadriiformes), and parrots (Psittaciformes). These three groups have different sensory requirements from the orofacial region. For example, beak-probing shorebirds use pressure information from the tip of the beak to find buried prey in soft substrates, whereas waterfowl, especially filter-feeding ducks, use information from the beak, palate, and tongue when feeding. Parrots likely require increased sensitivity in the tongue to manipulate food items. Thus, despite all sharing an enlarged PrV and feeding behaviors dependent on tactile input, each group has different requirements that have led to the independent evolution of a large PrV.

Morphological examination of the proximal ganglion of the vagus nerve in the pig.

This is the first report dealing with the localisation and morphology of the proximal (jugular) ganglion in the pig. Six 3-months-old pigs of both sexes were used in this study. Tissues were stained with three histological methods: Klüver-Barer counterstained with Cresyl violet, Haematoxylin-eosin and Mayer's haematoxylin. The localisation and morphological features of the ganglion and ganglionic neurones were described and discussed.

[Structure of visual pathways in the nervous system of fresh water pulmonary molluscs].

The central nervous system of freshwater pulmonary molluscs Lymnaea stagnalis and Planorbarins corneus was stained by the method of neurobiotin retrograde transport along optic nerve fibers. In the animals of both species, bodies and fibers of stained neurons are found in all ganglia except for the buccal ones. Afferent fibers of the optic nerve form a dense sensor neuropil located in a small volume of cerebral ganglia. Characteristic groups of neurons sending their processes into optic nerves both of ipsi- and of contralateral half of the body are described. Revealed among them are neurons of visceral and parietal ganglia, which simultaneously innervate both eyes as well as give projections into peripheral nerves. It is suggested that these neurons can perform function of integration of sensor signals and, on its base, regulate photosensitivity of retina as well as activity of peripheral organs. There is established the presence of bilateral connections of the mollusc eye with cells of pedal ganglia and statocysts, which seems to be the structural basis of manifestation of the known behavior forms associated with stimulation of visual inputs of the studied gastropod molluscs.

The preplacodal region: an ectodermal domain with multipotential progenitors that contribute to sense organs and cranial sensory ganglia.

The otic primordium belongs to a group of related structures, the sensory placodes that contribute to the paired sense organs - ear, eye and olfactory epithelium - and to the distal parts of the cranial sensory ganglia. Recent evidence suggests that despite their diversity, all placodes share a common developmental origin and a common molecular mechanism which initiates their formation. At the base of placode induction lies the specification of a unique "placode field", termed the preplacodal region and acquisition of this "preplacodal state" is required for ectodermal cells to undergo otic development. Here I review the molecular mechanisms that sequentially subdivide the ectoderm to give rise to the placode territory.

Electrical and pharmacological properties of petrosal ganglion neurons that innervate the carotid body.

The petrosal ganglion (PG) contains the somata of primary afferent neurons that innervate the chemoreceptor (glomus) cells in the carotid body (CB). The most accepted model of CB chemoreception states that natural stimuli trigger the release of one or more transmitters from glomus cells, which in turn acting on specific post-synaptic receptors increases the rate of discharge in the nerve endings of PG neurons. However, PG neurons that project to the CB represent only small fraction (roughly 20%) of the whole PG and their identification is not simple since their electrophysiological and pharmacological properties are not strikingly different as compared with other PG neurons, which project to the carotid sinus or the tongue. In addition, differences reported on the actions of putative transmitters on PG neurons may reflect true species differences. Nevertheless, some experimental strategies have contributed to identify and characterize the properties of PG neurons that innervate the CB. In this review, we examined the electrophysiological properties and pharmacological responses of PG neurons to putative CB excitatory transmitters, focusing on the methods of study and species differences. The evidences suggest that ACh and ATP play a major role in the fast excitatory transmission between glomus cells and chemosensory nerve endings in the cat, rat and rabbit. However, the role of other putative transmitters such as dopamine, 5-HT and GABA is less clear and depends on the specie studied.

Projection patterns of gustatory neurons in the suboesophageal ganglion and tritocerebrum of mosquitoes.

Mosquitoes are heavily dependent on gustatory information when feeding. Following the recent elucidation of the molecular basis of gustation in the malaria mosquito, we present a detailed study of primary central projections of gustatory receptor neurons into the brain in the malaria (Anopheles gambiae) and yellow fever (Aedes aegypti) mosquito. In the brain we provide a detailed map of the areas targeted and describe a number of intrinsic neural elements connecting primary taste areas to higher brain levels. The morphological features described are discussed and compared to earlier reports in other insects as, e.g., the fruitfly, Drosophila.

Comprehensive immunofluorescence and lectin binding analysis of vibrissal follicle sinus complex innervation in the mystacial pad of the rat.

The innervation of the vibrissal follicle sinus complexes (FSCs) in the mystacial pad of the rat was examined by lectin binding histofluorescence with the B subunit of Griffonia simplicifolia (GSA) and by immunofluorescence with a wide variety of antibodies for neuronal related structural proteins, enzymes, and peptides. Only anti-protein gene product 9.5 labeled all sets of innervation. Several types of mechanoreceptors were distributed to specific different targets by medium to large caliber myelinated axons. All were positive for 200 kDa neurofilament subunit, peripherin, and carbonic anhydrase. Their endings expressed synaptophysin. Labeling for the 160 kDa neurofilament subunit, calbindin, and parvalbumin varied. Anti-Schwann cell protein S100 was completely co-extensive with the axons, terminal arbors, and endings of the mechanoreceptor afferents including Merkel innervation. At least 15 different sets of unmyelinated innervation were evident based upon distribution and labeling characteristics. They consisted of four basic types: 1) peptidergic; 2) GSA binding; 3) peptidergic and GSA binding; and 4) nonpeptidergic and GSA negative (peptide-/GSA-). Previous studies had not revealed that several major sets of unmyelinated innervation were peptide-/GSA-. The unmyelinated innervation had detectable peripherin but not 160 kDa or 200 kDa neurofilament subunits. GSA-positive axons uniquely lacked anti-S100 immunoreactivity. The dense circumferentially oriented unmyelinated innervation of the inner conical body contained major sets of peptide-/GSA- and GSA innervation as well as a smaller peptidergic GSA component. A small contingent of sympathetic and possibly parasympathetic innervation was affiliated with microvasculature in the FSCs. This study confirms and refutes some previous hypotheses about biochemical and morphological relationships between peripheral innervation and sensory ganglion cells.

Intrinsic connections of the rat amygdaloid complex: projections originating in the lateral nucleus.

The amygdaloid complex receives sensory information from a variety of sources. A widely held view is that the amygdaloid complex utilizes this information to orchestrate appropriate species-specific behaviors to ongoing experiences. Relatively little is known, however, about the circuitry through which information is processed within the amygdaloid complex. The lateral nucleus is the major recipient of extrinsic sensory information and is the origin of many intra-amygdaloid projections. In this study, we reinvestigated the organization of intra-amygdaloid projections originating from the lateral nucleus using the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L). The lateral nucleus has highly organized intranuclear connections. Dense projections interconnect rostral and caudal levels of the lateral and the medial divisions of the nucleus, and the lateral and medial divisions of the lateral nucleus are also interconnected. The major extranuclear projections of the lateral nucleus are (in descending order of magnitude) to the accessory basal nucleus, the basal nucleus, the periamygdaloid cortex, the dorsal portion of the central division of the medial nucleus, the posterior cortical nucleus, the capsular division of the central nucleus, and the lateral division of the amygdalohippocampal area. The pattern of extranuclear projections varied depending on the rostrocaudal or mediolateral location of the injection site within the lateral nucleus. These findings indicate that intra-amygdaloid projections originating in the lateral nucleus are both more widespread and more topographically organized than was previously appreciated.

Afferent sources to the ganglion of the terminal nerve in teleosts.

Afferent sources to the ganglion (ggl) of the terminal nerve (TN) were studied in percomorph teleosts the tilapia and dwarf gourami. After tracer applications to the TN-ggl and the surrounding bulbus olfactorius, retrogradely labeled neurons were present in the area dorsalis telencephali pars posterior (Dp), area ventralis telencephali pars ventralis et supracommissuralis (Vv and Vs), nucleus tegmento-olfactorius of Prasada Rao and Finger (1984), and locus coeruleus. In the contralateral bulbus olfactorius labeled cells were observed, and terminals were seen in the TN-ggl. Tracer injection experiments to the possible sources of origin to the TN-ggl were then performed. Tracer applications to the nucleus tegmento-olfactorius labeled abundant terminals in the TN-ggl but labeled very few in the bulbus olfactorius proper. Retrogradely labeled neurons were present in the nucleus ventromedialis thalami, nucleus commissurae posterioris, area pretectalis pars dorsalis et ventralis, nucleus sensorius nervi trigemini, and formatio reticularis pars superius et medius. Tracer applications to the Dp or Vs/Vv labeled terminals mainly in the bulbus olfactorius proper. However, terminals to the TN-ggl were supplied from labeled axons on their way to the bulbus olfactorius. Tracer injections to the locus coeruleus labeled only a few fibers around the TN-ggl. These results suggest that the TN-ggl receives somatosensory and visual inputs from the nucleus tegmento-olfactorius and olfactory inputs from the bulbus olfactorius and telencephalic subdivisions, which receive secondary olfactory projections. The locus coeruleus may also send fibers to the TN-ggl.

Somatotopic organization of the facial lobe of the sea catfish Arius felis studied by transganglionic transport of horseradish peroxidase.

To reveal the somatotopical organization of the facial lobe (FL), a primary medullary gustatory nucleus in the sea catfish Arius felis, the central projections of the peripheral rami of the facial nerve innervating taste buds located across the entire body surface and rostral oral regions were traced by means of horseradish peroxidase neurohistochemistry. The maxillary barbel, lateral mandibular barbel, medial mandibular barbel, and trunk-tail branches project to four different longitudinal columns (i.e., lobules) extending rostrocaudally in the FL. The trunk-tail lobule, which is located dorsolateral to the barbel lobules, lies in the anterior two-thirds of the FL. The tail is represented in a more rostral portion of the trunk-tail lobule than the trunk, indicating that the rostrocaudal trunk axis is represented in the trunk-tail lobule in a posteroanterior axis. The pectoral fin branch ends in an intermediate region of the FL, whereas the hyomandibular, ophthalmic, lower lip, upper lip, and palatine branches terminate in discrete regions of the caudal one-third of the FL. These results reveal a sharply defined somatotopical organization of the FL of Arius and support the hypothesis that the number and lengths of the barbel lobules within the FL of catfishes are directly related to the number and relative lengths of the barbels. An additional subcolumn, the intermediate nucleus of the FL (NIF), which develops in the medioventral region of the caudal two-thirds of the FL, receives projections in a diffuse somatotopical fashion from the barbels, lower lip, and palatine branches. Trigeminal fibers of the barbel and lower lip branches project in a somatotopic fashion to the FL. The present findings suggest that the FL of Arius is highly organized somatotopically to detect, by tropotaxis, precise spatial information concerning taste and tactile stimuli in the environment.

Sensory ganglia as a target of autonomic and sensory nerve fibres in the guinea-pig.

The distribution of neuropeptide- (neuropeptide Y, substance P, vasoactive intestinal peptide) and catecholamine-synthesizing enzyme-immunoreactive axons in guinea-pig trigeminal, nodose, and cervical dorsal root ganglia was studied by double-labelling immunofluorescence in controls and after extirpation of either the cervical sympathetic trunk or the stellate ganglion; tyrosine hydroxylase- and dopamine-beta-hydroxylase-immunoreactive terminals in dorsal root ganglia were ultrastructurally investigated. Six neurochemically identifiable axons innervated the trigeminal ganglion, five kinds were found in the nodose and dorsal root ganglia. Two of them (catecholaminergic with and without neuropeptide Y) were of sympathetic origin and, besides their termination at arteries, provided a direct innervation of capsule cells of the trigeminal and cervical dorsal root ganglia facing the subarachnoid space. Varicosities which were interpreted as being of sensory origin were equally numerous in all ganglia, whereas those being likely of parasympathetic origin decreased in numbers from the trigeminal to the dorsal root and nodose ganglia. It is concluded that the sensory ganglia are the target of postganglionic sympathetic, parasympathetic and primary afferent neurons, each of which are specifically organized with respect to the neurochemical phenotype and inter- and intraganglionic distribution. Among other targets, these "nervi gangliorum" appear to be intimately linked to the ganglionic capsular cells and meningeal sheaths facing the liquor spaces.

Association of a choroidal ganglion cell plexus with the fovea centralis.

PURPOSE: After recently demonstrating an NADPH-diaphorase-, nitric oxide synthase (NOS)-positive ganglion cell plexus in the human choroid that was absent in rabbit and rat eyes, the authors extended their comparative studies to nonhuman primates and to subprimate mammals. METHODS: The authors investigated the choroids of diurnal cynomolgus monkeys with well-developed fovea centralis and accommodative systems; diurnal tree shrews without a fovea centralis or accommodative capacity; nocturnal owl monkeys with substantial accommodative capacity but without a fovea centralis; cats with an area centralis but no fovea centralis; and pigs without an area centralis or a fovea centralis. The latter two species have moderately developed ciliary muscles. Wholemounts of the choroid of eight cynomolgus monkey, two owl monkey, four tree shrew, four cat, and four pig eyes were stained for NADPH-diaphorase. In addition, frozen sections through the cynomolgus monkey choroid were stained for NOS and vasoactive intestinal polypeptide (VIP). RESULTS: In all species, the choroidal vessels were surrounded by NADPH-diaphorase-positive nerve fibers. A ganglion cell plexus, however, was seen only in cynomolgus monkey eyes. The ganglion cells stained for NOS and VIP. CONCLUSIONS: The presence of intrachoroidal nitrergic nerve cells restricted to species with a fully developed fovea centralis may indicate a functional correlation of these structures.

A comparative study of three cranial sensory ganglia projecting into the oral cavity: in situ hybridization analyses of neurotrophin receptors and thermosensitive cation channels.

Peripheral cranial sensory nerves projecting into the oral cavity receive food intake stimuli and transmit sensory signals to the central nervous system. To describe and compare the features of the cranial sensory ganglia that innervate the oral cavity, i.e., the trigeminal, petrosal, and geniculate ganglia (TG, PG, and GG, respectively), in situ hybridization was conducted using riboprobes for neurotrophin receptors (TrkA, TrkB, and TrkC), a neurotransmitter (substance P), and ion channels important for thermosensation (VR1 and TREK-1). In TG, all in six probes yielded positive signals to various extent in intensity and frequency. In addition, a strong correlation between the expression of VR1 and those of TrkA and substance P was observed as in the case of the dorsal root ganglia. In PG, positive signals to all six probes were also detected, and the correlation of expression was similar to that shown by TG. On the other hand, most cells in GG were positive to the TrkB probe, and a small number of cells were positive to the TrkC probe, but no significant signal was observed for the other four probes. These results indicate that TG and PG consist of cells that are heterogeneous in terms of neurotrophin requirement and somatosensory functions, and that GG seems to consist mainly of a homogeneous cell type, gustatory neurons. In conclusion, TG, PG, and GG, show gene expression characteristics intrinsic to the three ganglia. It is also concluded that TG and a portion of PG project several types of somatosensory nerves. This is consistent with the finding that GG and a portion of PG project gustatory nerves.

Cutaneous sensory nerve formations as studied with impregnation techniques: notes about a simple and reliable method.

In spite of the modern immunocytochemical methods employed in the study of peripheral sensory nerve formations, silver impregnations are still frequently used. This paper describes and discusses in detail a simple "Cajal-type" silver impregnation method suitable for the peripheral and central nervous systems, which offers excellent results when used in the study of sensory nerve formations. Essential features are (a) the use of a pretreatment solution containing sodium tartrate and picric acid; (b) the short time needed for the whole impregnation process; (c) its simplicity, and (d) the ability to show the axonal elements of sensory nerve formations and other very thin nerve fibres too difficult to be demonstrated with immunohistochemical methods. Taken together, these properties allow this method to be included among the so-called "routine methods."

Structural diversity of the ordinary and specialized lateral line organs.

Lateral line organ, a superficial sensory system in amphibia and fish which provides the animal with information about its surrounding environment, is divided classically into two main different types, ordinary and specialized, whose functions are mechanoreceptive and electroreceptive, respectively. Although it has great diversity, the basic sensory unit, which is usually called "neuromast," is composed of sensory cells embedded in accessory cells. The functions of the latter are to support the sensory cells and to secrete the material that covers the organs, forming a cupular structure or filling a canal which enables the organ to communicate with the exterior. Sensory cells of mechanoreceptive neuromasts have a tuft of processes included in the cupular material; these are a kinocilium and a group of stereocilia with a typical staircase arrangement. The displacement of the stereocilia towards or away from the kinocilium produces different stimuli. The electroreceptive organs are more diverse. They include ampullary and tuberous organs. The latter can be subdivided into different types: knollenorgans, mormyromasts, gymnarchomasts, etc. All of these present a great diversity among species, but their morphology is less reported than that of the mechanoreceptive organs. This paper summarizes the structural features of the main different types of lateral line organs, as well as their taxonomic distribution and different patterns of distribution along the surface of the animal.

Localization of neurons projecting into the extrinsic penile smooth musculature of the pig: an experimental study on the retractor penis muscle.

The aim of this study was to locate in male pigs the sensory and autonomic ganglia innervating the retractor penis muscle (RPM), which was taken as an experimental model of the genital smooth musculature. The retrograde neuronal tracers horseradish peroxidase (HRP), Fast Blue (FB), and diamidino yellow (DY) were injected into the bulbopenile portion of the left RPM. The tracers highlighted a different affinity for the neuronal structures, although labelled cells supplying the RPM were generally found in bilateral dorsal root ganglia (DRGs, S1-S3), in bilateral paravertebral ganglia (PaGs, L2-S3), and in the left and right caudal mesenteric ganglia (CMGs). The mean number of labelled FB cells was 795 (range, 645-952) in DRGs, 16046.25 (range, 10226-18742) in PaGs, and 635.25 (range, 333-786) in CMGs. The mean diameter of pseudounipolar DRG cells was 60-75 microm, while the multipolar neurons of PaGs and CMGs had dimensions varying between 20-50 microm and 20-30 microm, respectively.