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PubMed1983

Projections from the pretectal complex to the thalamic lateral dorsal nucleus of the cat.

The subcortical projections to the lateral dorsal nucleus (LD) of the cat thalamus were studied with retrograde transport techniques. Deposits of horseradish peroxidase (HRP) or fluorescent tracers were placed unilaterally in LD of adult cats, using electrophoretic or pressure injection techniques. Following post-injection survival periods of 1, 2 or 3 days, HRP retrogradely labeled cells were identified in sections reacted with benzidine dihydrochloride; fluorescent labeled cells were identified by fluorescent microscopy. Injections in LD result in retrogradely labeled neurons in all nuclei of the pretectal complex, including the nucleus of the optic tract (NTO), the posterior pretectal nucleus (NPP), the anterior pretectal nucleus (NPA), the pretectal olivary nucleus (NOL), and the medial pretectal nucleus (NPM). Small electrophoretic injections of HRP were used to investigate a possible topographic organization of the pretectal projections. Results from a variety of injection sites indicate only a subtle rostral-caudal gradient. That is, small injection sites in rostral LD result in retrograde labeling of neuron somata in the rostral parts of NTO, NPA and NPP, and throughout NPM. Injections in caudal LD result in labeled cells more caudally situated in NTO, NPA, NPP, and throughout NPM. Injections in the pulvinar (Pul) also result in retrogradely labeled cells in the pretectal complex, particularly NTO, NPP, and NOL. Experiments with injections of distinguishable fluorescent tracers in LD and Pul reveal that many more cells project to Pul than to LD. These experiments also reveal that while neurons that project to LD are intermingled with neurons that project to Pul, the two projections originate from separate subpopulations of cells. These results are discussed in regard to phylogenetic comparison of pretectal projections and subcortical pathways of sensory input to the limbic system.

Afferent Pathways↗
PubMed1978

Multiple branching of cerebellar efferent projections in cats.

The retrograde labeling of neurons in the deep cerebellar nuclei with horseradish peroxidase was used to compare the morphological characteristics of neurons in the dentate and interposed nuclei projecting in the cerebellothalamic, cerebello-olivary, and cerebellar nucleocortical pathways. The results from these studies demonstrated that cerebellothalamic and nucleocortical projections from the dentate and interposed nuclei originate from similar populations of spindle- and multipolar-shaped neurons with somal diameters throughout the range of cells present in the deep nuclei. However, only spindle-shaped neurons with somal diameters of 9--15 microns project in the cerebello-olivary pathway. From these anatomical studies, it was concluded that some of the neurons in the dentate and interposed nuclei which project to the thalamus, inferior olive, and cerebellar cortex have similar morphological characteristics. Electrophysiological experiments were carried out to investigate whether or not some of these neurons project to all three sites viaaxon collaterals. From stimulus sites in the thalamus, inferior olive, and cerebellar cortex, numerous neurons were antidromically activated in the cerebellar nuclei. Collision experiments between these antidromic responses confirmed that single neurons projected to all three of these sites. These studies therefore demonstrate that the axons of some neurons in the dentate and interposed nuclei have collateral branches in both the ascending and descending limbs of the brachium conjunctivum as well as in the cerebellar nucleocortical pathway. Functional implications of the collateral branching of cerebellar efferent projections are discussed.

Animals↗
PubMed1986

Cerebellar projections from the cervical enlargement: an experimental study with silver impregnation and autoradiographic techniques in the cat.

The cerebellar projection of neurons in the cervical enlargement was investigated in cats using two neuroanatomical methods, the successive degeneration method (Sherrington and Laslett 1903) and the autoradiographic tracing technique (3H-leucine). With both methods projections were found to the anterior lobe, posterior vermis and paramedian lobule. In the anterior lobe the projection was bilateral mainly to the vermal part of lobules I-V and the adjoining part of lobule VI, although some projection was also observed bilaterally to lobules I-VI lateral to the vermis. In the posterior vermis projection was found bilaterally to lobule VIII and in neighboring parts of lobule VII B. In the paramedian lobule the projection was mainly ipsilateral to the lesions/injections to the pars copularis and the adjoining part of the pars posterior. Only minor differences between the two methods were noted. In conclusion, spinocerebellar neurons project mainly to the vermal area of the anterior lobe (including the most anterior part of lobule VI), to lobules VII B and VIII and to the ipsilateral paramedian lobule.

Animals↗
PubMed1983

Lack of collateral thalamocortical projections to fields of the first somatic sensory cortex in monkeys.

Retrograde axoplasmic transport of differently colored fluorescent dyes was used to determine the distributions and relative proportions of cells in the ventrobasal complex of the monkey thalamus that project to each of the architectonic fields of the first somatic sensory cortex. Fast blue was injected into portions of area 3a identified by first recording short latency, multiunit responses to electrical stimulation of Group I afferents in a muscle nerve of the forelimb or hindlimb. Nuclear Yellow was later injected into a part of area 2 responding to maximal electrical stimulation of the same nerve. In experiments that served as controls, Fast Blue was injected into area 3b and Nuclear Yellow into area 1. The results confirm the division of the ventrobasal complex into: (i) a central core with an inner part projecting to area 3b and a surrounding part projecting area 1; (ii) a peripheral shell projecting to areas 3a and 2 (Jones et al. 1982). A far greater proportion of VB cells projects to areas 3b or 3a than to areas 1 or 2. In portions of the ventrobasal complex projecting to two areas, no cells were double labelled provided that the injections of blue and yellow dyes did not overlap. The results, thus, show a lack of collateral thalamocortical projections to the fields of the postcentral gyrus and, when taken in conjunction with other data, imply the independent relay of modality specific information through the thalamus.

Afferent Pathways↗
PubMed1986

Non-cholinergic afferents determine the distribution of the cholinergic septohippocampal projection: a study of the AChE staining pattern in the rat fascia dentata and hippocampus after lesions, X-irradiation, and intracerebral grafting.

The acetylcholinesterase (AChE) activity of the rat hippocampus and fascia dentata depends on an intact septohippocampal connection, and histochemical staining for AChE is commonly used to monitor the distribution of the cholinergic septohippocampal projection. It is also characteristic that the laminae of low or moderate to dense AChE staining in the hippocampus and fascia dentata coincide with the terminal fields of the major non-cholinergic, afferent pathways. While studying lesion-induced collateral sprouting and aberrant axonal growth of these pathways we observed that the AChE staining pattern changed in accordance with the reorganized distribution of the non-cholinergic pathways, and this occurred even without direct interfering with the septohippocampal projection itself. Widening and narrowing of the medial perforant path and mossy fiber terminal zones thus resulted in corresponding changes in the bands of AChE staining normally associated with these zones. Expansion of the commissural-associational hippocampodentate projections and the lateral perforant path was in a similar way paralleled by a widening of the AChE-poor zones which normally overlap with the termination of these projections. Observations of the same kind were made in intracerebral transplants of fascia dentata innervated by various host afferents, and in rats subjected to neonatal X-irradiation, where the mossy fiber projection is reduced and aberrant perforant pathways project into CA3 due to a reduced formation of granule cells. The observed sets of changes with linkage between the different non-cholinergic projections and the activity of AChE in their respective terminal fields were accordingly reproduced under several different experimental conditions. It could not be explained alone by interaction between the septal afferents and their target cells. We therefore conclude that the density and laminar distribution of the AChE activities within the hippocampus and fascia dentata are determined at least in part by the major afferent, non-cholinergic nerve connections. We suggest that the effect occurs through direct axonal interaction or through changes in the receptiveness of the common dentate and hippocampal target cells.

Acetylcholinesterase↗
PubMed1988

Retinofugal projections in hedgehog-tenrecs (Echinops telfairi and Setifer setosus).

Using the autoradiographic tracing technique the retinal projections were studied in the tenrecs, Echinops telfairi and Setifer setosus (insectivora, tenrecidae). Bilateral projections were found to the n. suprachiasmaticus, the anterior hypothalamic area, the dorsal and ventral lateral geniculate bodies, the pretectal olivary nucleus and the superior colliculus. The contralateral projections were usually more intense than the ipsilateral ones except the retinohypothalamic connections. A partial segregation of the projection fields from both eyes was present in the dorsal and ventral lateral geniculate bodies. In the superior colliculus retinal fibers predominantly involved the stratum zonale and the upper portion of the stratum griseum superficiale on both sides. The projections to the deeper portion of the colliculi were rather faint, particularly on the ipsilateral side. Target areas receiving contralateral projections exclusively were the periamygdaloid area (labeled only in Setifer), the terminal accessory nuclei including the n. tractus optici and the inferior colliculus. The data are compared with other species. The most striking finding may concern the projection to the medial terminal nucleus being quite prominent in marsupials and most eutherian mammals (including the erinaceomorphous hedgehogs), but greatly reduced in tenrecs and primates.

Animals↗
PubMed1989

A quantitative analysis of the crossed septohippocampal projection in the rat brain.

The projection from the medial septal-diagonal band complex (MSDB) to the hippocampal formation is generally considered to be primarily an uncrossed projection. The present study examined the number of MSDB neurons which project to the contralateral hippocampus, the position of these cells, their identity as either cholinergic or GABAergic, and the question of bilateral collateral projections. The fluorescent dyes Fluoro-Gold or diamidino yellow were injected into 5 equally-spaced sites along the septotemporal extent of the right hippocampus of adult female Sprague-Dawley rats. In some animals True Blue (5%) was also injected in a similar fashion into the left hippocampus. Five days later the brains were processed for fluorescence microscopic examination. The number of retrogradely labeled cells on each side was counted in every fifth section (200 microns interval) through the MSDB and the percentage of contralaterally projecting neurons was calculated. Averaging across all sections and all brains, it was found that approximately 15% of the medial septal neurons and 17% of the diagonal band neurons project to the contralateral hippocampus. Most of the labeled neurons, both ipsilateral and contralateral, were present in the caudal half of the MSDB. Within the medial septum contralaterally placed cells were distributed uniformly throughout the mediolateral extent and some of these stained immunocytochemically for choline acetyltransferase or glutamic acid decarboxylase. In brains in which diamidino yellow was injected into the right hippocampus and True Blue into the left numerous neurons were observed to contain both dyes, thus indicating projections to both hippocampi.

Animals↗
PubMed1988

Development of retinofugal neuropil areas in the brain of the alpine newt, Triturus alpestris. II. Topographic organization and formation of projections.

The development of retinal projections and the formation of their retinotopic organization were studied by means of anterograde transport of horseradish peroxidase in the newt, Triturus alpestris. All tracts found in the adult on the contralateral brain side are established during embryonic stages. At this stage a few uncrossed fibers are also detectable. Retinal fibers project first to the contralateral optic tectum. These are followed by contralateral projections to the thalamic recipient areas. Beginning at embryonic stages, the projections from the retinal quadrants into the optic tectum are topographically organized. The other terminal areas innervated by the marginal optic tract (MaOT) show a topographic order from midlarval stages. The terminal areas innervated by the medial optic tract (MeOT) show no clear topographic organization at any stage. The contralateral projection of the MeOT originates from the central area of the retina, whereas the uncrossed projection originates from the temporal peripheral retina. Ipsilateral (uncrossed) retinal projections develop during metamorphic climax. The MeOT is more distinct than the MaOT. The latter shows a clear retinotopic organization. The topography of the ipsilateral MaOT and its corresponding terminal areas are mirror-symmetric to the contralateral tract and terminal areas.

Animals↗
PubMed1991

The GABAergic cerebello-olivary projection in the rat.

Immunocytochemical detection of glutamate decarboxylase (GAD), the predominant biosynthetic enzyme of gamma-aminobutyric acid (GABA), reveals the presence of a dense GABAergic innervation in all parts of the inferior olive. One brain center that provides a substantial projection to the inferior olive is the cerebellar nuclei, which contain many small GABAergic neurons. These neurons were tested as a source of GABAergic olivary afferents by combining retrograde tract tracing with GAD immunocytochemistry. As expected from previous studies, injections of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) into the inferior olive retrogradely label many small neurons in the interposed and lateral cerebellar nuclei and the dorsal part of the lateral vestibular nucleus, and fewer neurons in the ventro-lateral region of the medial cerebellar nucleus. These projections are predominantly crossed and are topographically arranged. The vast majority, if not all, of these projection neurons are also GAD-positive. The relative contribution of this projection to the GABAergic innervation of the inferior olive was tested by lesion of the cerebellar nuclei, or the superior cerebellar peduncle. Within 10 days the lesion eliminates most GAD-immunoreactive boutons in the principal olive, the rostral lamella of the medial accessory olive, the ventrolateral outgrowth, and the lateral part of the dorsal accessory olive ventral fold. Thus, the effectiveness of this depletion demonstrates that the cerebellar nuclei provide most of the GABAergic innervation to regions of the inferior olive known to receive a cerebellar projection. Moreover, when the lateral vestibular nucleus is damaged, the dorsal fold of the dorsal accessory olive is depleted of GABAergic boutons. The synaptic relations that boutons of the GABAergic cerebello-olivary projection share with olivary neurons were investigated at the electron microscopic level by GAD-immunocytochemistry, anterograde degeneration of the cerebellar axons or anterograde transport of WGA-HRP. All of these methods confirm that GABAergic, cerebello-olivary axon terminals contain pleomorphic vesicles, and synapse on various portions of olivary neurons, and especially on dendritic spines within glomeruli, often in very close proximity to the gap junctions that characteristically couple the dendritic profiles. These results demonstrate four major points: that virtually all of the GABAergic, and presumably inhibitory, neurons of the cerebellar and dorsal lateral vestibular nuclei are projection neurons; that a large portion of the inferior olive receives GABAergic afferents from the cerebellar nuclei; that a portion of the dorsal accessory olive receives GABAergic afferents from the dorsal lateral vestibular nucleus; and that cerebello-olivary fibers often synapse near gap junctions, and therefore could influence electrical coupling of olivary neurons.

Animals↗
PubMedDate not supplied

Filler injection enhances the projection of the reconstructed nipple: an original easy technique.

BACKGROUND: Reduced nipple projection is the main reason for unsatisfactory nipple-areola complex reconstruction, and many techniques have been proposed to maintain projection of the reconstructed nipple. METHODS: For 70 patients, 90 nipples were reconstructed using either a small wedge from the labia minora (LMW) (n=70) or nipple sharing (NS) (n=20). Two months after reconstruction, each reconstructed nipple was injected with DermaLive. Second and third injections were performed 2 and 5 months later. The injected volume was tailored to the desired projection. Nipple projection was measured at the moment of implant, before and after each injection, and 6 and 12 months after the last injection. RESULTS: Nipple projection was satisfactory in all cases and comparable with that of the contralateral nipple. The average nipple projection at 6 months was 5.8 mm in the LMW group and 3.8 mm in the NS group (p<0.01) and, respectively, 5.6 mm and 3.5 mm at 12 months (p<0.01). No complications occurred, except for one positron emission tomography (PET) false-positive result. CONCLUSIONS: The described method is simple and safe. It provides precise projection with no need for intraoperative forecasting of tissue reabsorption. The result was better for the LMW patients, perhaps because of their higher distensibility.

Acrylates↗
PubMed2002

Conservation and development projects in the Brazilian Amazon: lessons from the Community Initiative Program in Rondônia.

Community-based conservation and development has become the prevailing programmatic paradigm of conservation organizations and development donors over the last 20 years, spawning a myriad of integrated conservation and development projects (ICDP) around the world. Appealing for its ambitious aspiration to harmonize sustainable economic development at the local level with the conservation of legally established protected areas (e.g., parks and reserves), the ICDP approach recently has drawn criticism from conservation biologists for failing to ensure adequate protection of biodiversity. Development planners and economists have also raised questions about the financial sustainability of ICDPs in practice and the replicability of the model from highly local contexts to larger regional scales. This paper briefly reviews the central elements of the concept of integrated conservation and development and the emerging debate over its effectiveness. A description of the Community Initiative Program (CIP), a pilot program of the Rondônia Natural Resources Management project (PLANAFLORO) in the western Brazilian Amazon state of Rondônia, follows. The CIP is a significant experiment because it boldly attempted to apply the principles of ICDP to the regional scale involving numerous different communities in one program simultaneously. Based on the author's mid-term review of the CIP in 1999, the development and conservation impacts of the program are considered. While the CIP has not significantly curbed the degradation of protected areas in Rondônia as intended, the evidence suggests lower rates of deforestation in municipios (i.e. counties) with the highest concentrations of CIP projects. Although the economic development impacts are mixed, approximately 50% of the projects delivered tangible benefits to local communities. Lessons learned from the CIP are presented in the final section. Among the lessons learned from the CIP, detailed in the final section, are several that will be familiar to other ICDP evaluators: the importance of thematic coherence in initial project design, the need for explicit attention on environmental conservation objectives, deficient institutional capacity of implementing organizations, inadequate attention to women's concerns and roles in community projects, and lack of technical criteria for measuring project sustainability.

Agriculture↗
PubMed2000

RESEARCH: Projected Climate Change Effects on Winterkill in Shallow Lakes in the Northern United States.

/ Each winter, hundreds of ice-covered, shallow lakes in the northern United States are aerated to prevent winterkill, the death of fish due to oxygen depletion under the ice. How will the projected climate warming influence winterkill and the need to artificially aerate lakes? To answer this question, a deterministic, one-dimensional year-round water quality model, which simulates daily dissolved oxygen (DO) profiles and associated water temperatures as well as ice/snow covers on lakes, was applied. Past and projected climate scenarios were investigated. The lake parameters required as model input are surface area, maximum depth, and Secchi depth as a measure of radiation attenuation and trophic state. The model is driven by daily weather data. Weather records from 209 stations in the contiguous United States for the period 1961-1979 were used to represent past climate conditions. The projected climate change due to a doubling of atmospheric CO(2) was obtained from the output of the Canadian Climate Center General Circulation Model. To illustrate the effect of projected climate change on lake DO characteristics, we present herein DO information simulated, respectively, with inputs of past climate conditions (1961-1979) and with a projected 2 x CO(2) climate scenario, as well as differences of those values. Specific parameters obtained were minimum under-ice and lake bottom DO concentration in winter, duration of under-ice anoxic conditions (<0.1 mg/liter) and low DO conditions (<3 mg/liter), and percentage of anoxic and low DO lake volumes during the ice cover period. Under current climate conditions winterkill occurs typically in shallow eutrophic lakes of the northern contiguous United States. Climate warming is projected to eliminate winterkill in these lakes. This would be a positive effect of climate warming. Fish species under ice may still experience periods of stress and zero growth due to low DO (<3 mg/liter) conditions under projected climate warming.

Journal Article↗
PubMed2004

Rotations in a vertebrate setting: evaluation of the symmetry group of the disynaptic canal-neck projection.

Organizational structures intrinsic to nervous systems can be more precisely analyzed and compared with other logical structures once they are expressed in mathematical languages. A standard mathematical language for expressing organizational structure is that of groups. Groups are especially well suited to organizational structures involving multiple symmetries such as spatial structures. The vestibular system is widely believed to mediate many neural functions involving spatial structure. The vestibular nuclei receive direct projections from the vestibular endorgans, the semicircular canals and the otolith organs. The near-orthogonal directions of the semicircular canals are embedded in the bone. However, those canal directions are external to the nervous system. This study addresses the way the three-dimensional space of rotations is also embedded in the group structure of neural connectivity. Although we know a great deal about physical rotation, it is not clear that nervous systems organize rotations in the same way as physicists do. It would make sense for nervous systems to organize rotations in such a way as to provide physiologically relevant information about performing or compensating for rotations. The vestibular nuclei, which might be expected to display an organization that binds rotations into a rotation space, do not give a clear organization. This may be because of the multiplicity of spatial functions performed by the vestibular nuclei; rather than one spatial organization, the vestibular nuclei are likely to accommodate multiple, related spatial organizations. This study evaluates one particular data set from the literature that specifies the organization of the disynaptic canal-neck projection; other projections and neuronal populations may have other intrinsic organizations. The data are evaluated directly for their symmetry group. In the symmetry group, the vertebrate requirement that physiology have a right and left is found to be satisfied in two ways: (i) by a hexagonal symmetry arising from the right-left doubling of front and back, (ii) along with separate organizations on the two sides that may be required to operate independently to some extent. The eight observed muscle innervation patterns from the data are the complete set of possible combinations of inhibitory/excitatory polarities from three canal pairs. These eight innervation patterns are organized as the vertices of a cube. The two types of side muscles provide the vertical direction. As the head rotates in physical space, the cube rotates in sensorimotor space. Like the canal-neck projection, otolith projections and proprioceptive afferents contact both the vestibular nuclei and neck motoneurons. They may have a similar organization, perhaps with extensions of the same pattern. Otherwise, like a checkerboard superimposed over a paisley, they will form an overlapping organization with the disynaptic canal-neck projection. Further research is required to determine whether the sensorimotor spatial structure of the canal-neck projection is widespread in nervous systems or whether there are several complete structures that are fragmented and reintegrated.

Animals↗
PubMed2003

Cells of origin of vagal motor neurons projecting to different parts of the stomach in the rat: confocal laser scanning and electron microscopic study.

Parasympathetic motor neurons in the dorsal motor nucleus of the vagus (DMV) innervate the stomach by way of the gastric and hepatic branches of the vagus nerve. To investigate whether single neurons of the DMV provide collateral innervations to various parts of the stomach, we injected the retrograde tracer Fluoro-Gold (FG) into the cardia and the retrograde tracer cholera toxin subunit b (CTb) into the antrum or the pylorus of the same animal. Both retrogradely FG-labeled and CTb-labeled neurons were found throughout the DMV. Almost all CTb-labeled neurons (97%) were double-labeled with FG after injection of FG into the cardia and CTb into the antrum, while only a few CTb-labeled neurons (11%) were double-labeled with FG after injection of FG into the cardia and CTb into the pylorus. Thus, the cardia and the antrum received collateral projections, but the pylorus received projections mainly from different neurons in the DMV. These results indicate that different neurons in the DMV activate either the cardia or the pyloric sphincter muscles. We also labeled, retrogradely, the neurons projecting to the cardia and the pylorus in the DMV with cholera toxin-conjugated horseradish peroxidase (CT-HRP) to examine their ultrastructural characteristics. Although the neurons projecting to the cardia (21.6x15.0 microm, 248.0 microm2 per section) were significantly smaller than the neurons projecting to the pylorus (27.5x15.9 microm, 323.2 microm2 per section), their ultrastructural appearances were similar. Both types of neurons were small-to-medium sized, round or oval in shape, and generally had a small amount of cytoplasm containing a few Nissl bodies and a round nucleus. The average number of axosomatic terminals per section was low in the neurons projecting to the cardia (2.3) and the neurons projecting to the pylorus (3.0). Almost all axon terminals contacting these motor neurons contained round synaptic vesicles and made asymmetric synaptic contacts (Gray's type I).

Animals↗
PubMed1998

New indirect pathways subserving the pupillary light reflex: projections of the accessory oculomotor nuclei and the periaqueductal gray to the Edinger-Westphal nucleus and the thoracic spinal cord in rats.

The pupillary light reflex (PLR) is under the control of retinal ganglion cells projecting to the olivary pretectal nucleus (OPN). The OPN has a major projection to the Edinger-Westphal (EW) nucleus, which exerts its parasympathetic action on the iris musculature via the ciliary ganglion. The accessory oculomotor nuclei (AON) and the periaqueductal gray (PAG) receive input from the OPN and influence the PLR. The present study in rats aimed to elucidate the possible projections from the AON and PAG to the EW nucleus. The anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) was iontophoretically injected into the interstitial nucleus of Cajal (INC), the nucleus of the posterior commissure (NPC), the nucleus of Darkschewitsch (ND) and the rostral part of the PAG. The projections were studied at the light and electron microscopic level. The INC, NPC and ND have small projections to the EW nucleus, whereas the rostral part of the PAG densely projects to the EW nucleus. Without exception INC, NPC, ND and PAG varicosities are presynaptic to dendritic profiles in the EW nucleus and contain electron dense mitochondria, round vesicles and make asymmetric synaptic contacts. In addition the ND and PAG project to the thoracic level of the spinal cord. The fibres are presynaptic to dendritic profiles and contain electron dense mitochondria, round vesicles and make asymmetric synaptic contacts. The present observations allow the conclusion that the parasympathetic preganglionic neurons in the EW nucleus are not only controlled by the OPN-EW pathway but also by indirect pathways running via the AON and PAG. Moreover light-sensitive information is also transferred via an OPN-PAG-spinal cord pathway to the sympathetic superior cervical ganglion (SCG) that innervates the iris, suggesting that the PAG may have an integrative function in the sympathetic and parasympathetic control of the PLR.

Animals↗
PubMed2000

Central projections from contact chemoreceptors of the locust ovipositor and adjacent cuticle.

Contact chemoreceptors (basiconic sensilla) located on the ovipositor and genital segments of the locust serve to control the chemical features of the substrate before and during oviposition. They occur dispersed and also crowded in fields between mechanosensory exteroceptors sensitive to touch or wind (trichoid and filiform sensilla). The central nervous projections of the four chemosensory and one mechanosensory neurons from single basiconic sensilla were stained selectively, focusing on receptors on the ovipositor valves, which usually contact the substrate during the pre-oviposition probing movements. All axons and neurites from one contact chemoreceptor usually stay close together in most of their projections. Segregation occurs mainly when single axons terminate in one neuromere while the others proceed to a different neuromere or ganglion. For projections from one chemoreceptor, there is evidence neither for functional segregation of mechanosensory from chemosensory afferent terminals nor for specific segregation between different chemosensory afferents. The projections from sensilla of dorsal cuticle tend to project rather uniformly along the midline of the terminal ganglion. Comparative staining of touch- and wind-sensitive hair receptor neurons shows mostly central projections, similar to those of neighbouring contact chemoreceptors. From the typical intersegmental projections of most primary afferents and from the lack of segregation into glomerular structures, we conclude that integration of chemosensory information from the genital segments is distributed in the terminal and the 7th abdominal ganglion.

Animals↗
PubMed1998

Different subpopulations of cholinergic and nitrergic myenteric neurones project to mucosa and circular muscle of the guinea-pig gastric fundus.

Since the stomach lacks a well-developed ganglionated submucous plexus, the somata of enteric neurones innervating the muscle or the mucosa have to be localised within the myenteric plexus. The aim of this study was to determine the projection pathways and the neurochemical coding of myenteric neurones innervating these different targets in the gastric fundus. Myenteric cell bodies projecting to the mucosa or the circular muscle were retrogradely labelled by mucosa or muscle application of the fluorescent tracer DiI and subsequently characterised by their immunoreactivity for choline acetyltransferase (ChAT), nitric oxide synthase (NOS), substance P (SP) and/or neuropeptide Y (NPY). On average 143+/-91 and 89+/-49 myenteric neurones were labelled from the mucosa and the circular muscle, respectively. DiI-labelled neurones were either ChAT- or NOS-positive. DiI-labelled ChAT-positive neurones were mainly ascending and outnumbered NOS-positive neurones, which were mainly descending (79.3+/-6.2% vs 20.7+/-6.2% for mucosa neurones; 69.3+/-11.1% vs 30.7+/-11.1% for muscle neurones). Three ChAT-positive subpopulations (ChAT/-, ChAT/SP, ChAT/NPY) and two NOS-positive subpopulations (NOS/-, NOS/NPY) were found. ChAT/SP neurones projected mainly to the circular muscle (36.1+/-11.9% of the cholinergic muscle neurones; mucosa projection: 8.0+/-2.1%), whereas ChAT/NPY neurones projected mainly to the mucosa (38.1+/-9. 2% of the cholinergic mucosa neurones; muscle projection: 5.7+/-2. 4%). NOS/- cells projected predominantly to the muscle. This study demonstrates polarised pathways in the myenteric plexus consisting of ascending ChAT and descending NOS cells that innervate the circular muscle and the mucosa of the gastric fundus. The ChAT/SP neurones might function as circular muscle motor neurones, whereas ChAT/NPY neurones might represent secretomotor neurones.

Animals↗
PubMed2001

Projections of excitatory and inhibitory motor neurones to the circular and longitudinal muscle of the guinea pig colon.

The aim of this study was to identify myenteric pathways to the circular and longitudinal muscle of the guinea pig proximal colon. To identify excitatory and inhibitory muscle motoneurones, we applied the neuronal retrograde tracer DiI onto the circular or longitudinal muscle layer and performed additional immunohistochemistry for nitric oxide synthase (NOS) and choline acetyltransferase (ChAT). On average 166 +/- 81 circular muscle motoneurones (CMMN) and 100 +/- 74 longitudinal muscle motoneurones (LMMN) were labelled by DiI tracing. Myenteric pathways innervating the muscle were either ascending (DiI-labelled neurones with oral projections) or descending (DiI-labelled neurones with anal projections). The circular muscle was preferentially innervated by ascending pathways (66.0 +/- 9.1%). Most ascending CMMN were ChAT-positive (87.2 +/- 8.5%), whereas descending CMMN were mainly NOS-positive (82.3 +/- 14.6%). Most ascending (62.2 +/- 11.1%) and descending (82.0 +/- 12.5%) CMMN had circumferential projection preferences (circumferential projections were longer than projections along the longitudinal gut axis). In contrast to the polarised projections to the circular muscle, the longitudinal muscle was equally innervated by ascending (46.2 +/- 15.1%) and descending (53.9 +/- 15.1%) neurones. Ascending and descending pathways to the longitudinal muscle consisted predominantly of ChAT-positive neurones (98.1 +/- 1.9% and 68.0 +/- 8.5%, respectively), and both pathways had prominent longitudinal projection preferences. Only 25.5% of the descending LMMN were NOS-positive. In conclusion, the circular muscle in the proximal colon is innervated by descending inhibitory (NOS-positive neurones) and ascending excitatory (ChAT-positive neurones) pathways. In contrast, the longitudinal muscle is primarily innervated by ascending and descending excitatory motoneurones, and only a small proportion of the descending pathway consisted of inhibitory motoneurones.

Animals↗