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PubMed1997

[Digital subtraction dacrocystography].

The method of digital subtraction is based on the ability to eliminate interfering shadows from the X-ray picture, which makes it possible to make the parts of the picture containing contrast substance more visible. Digital subtraction dacryocystography makes better and more detailed imaging of the lacrimal pathways possible, in particular in the proximal part of the efferent lacrimal pathways, as compared with conventional dacryocystography. This is important for more detailed assessment of the necessary surgical intervention on the lacrimal pathways and its prognosis. The advantage is the possibility to deposit the image in the memory of the instrument as well as its digital processing and the smaller radiation load to which the lens is exposed. The authors examined by the method of digital subtraction dacryocystography 25 patients with disorders of the efferent lacrimal system and present some normal and pathological findings of the lacrimal pathways.

Humans↗
PubMed1988

The origins and trajectories of somatostatin reticulospinal neurons: a potential neurotransmitter candidate of the dorsal reticulospinal pathway.

Somatostatin (SOMA)-immunoreactive neurons present in the nucleus gigantocellularis and nucleus raphe magnus formed the origins of a descending pathway from the rostral medulla to the spinal cord. This descending pathway was traced through the central medullary tegmentum and dorsolateral funiculus to innervate the dorsal horn. The location, trajectories and presumed inhibitory nature of SOMA in the spinal cord suggest that SOMA maybe a potential neurotransmitter candidate for the classic dorsal reticulospinal pathway.

Animals↗
PubMed1998

Right ventricular infarction causes heterogeneous autonomic denervation of the viable peri-infarct area.

BACKGROUND: Because efferent autonomic pathways to the right ventricle (RV) differ from the efferent autonomic projections to the left ventricle (LV), we assessed the effects of RV infarction on this innervation. METHODS AND RESULTS: We measured the ventricular effective refractory period (ERP) shortening in response to bilateral ansae subclaviae stimulation and ERP lengthening induced by bilateral vagal stimulation as markers of autonomic innervation before and after RV myocardial infarction (RVMI) produced by coronary ligation (n=28 dogs) or intracoronary latex injection (n=18 dogs) into a marginal branch of the right coronary artery in open-chest anesthetized dogs. In each dog, ERPs measured in viable peri-infarct area at two RV outflow tract (RVOT) sites and two septal and four lateral sites at the RV free wall after RVMI showed reduced or absent ERP shortening during bilateral ansae subclaviae stimulation laterally, septally, and at RVOT sites 3 hours after RVMI. ERP shortening in response to infused norepinephrine was still present. Bilateral vagal stimulation during background norepinephrine infusion (0.10 to 0.25 microg/kg per minute) lengthened the ERP at all test sites before latex injection. After transmural RVMI, vagally induced ERP prolongation was attenuated or lost at lateral, septal, and RVOT test sites. CONCLUSIONS: RVMI causes sympathetic and vagal denervation at viable sites at the RVOT, lateral, and, to a lesser extent, septal sides of the viable peri-infarct area. Autonomic denervation in the RVOT might contribute to the development of ventricular tachyarrhythmias after the acute stage of myocardial infarction involving the RV.

Animals↗
PubMed1987

[Anatomy of the central auditory pathway. Demonstration with horseradish peroxidase in the guinea pig].

The neurones of the afferent and efferent auditory pathways were labelled by axonally transported horseradish peroxidase. The first neurone of the ascending system is the acoustic nerve with the spiral ganglion. These fibres terminate mainly in the ventral cochlear nucleus (VCN). The neurones of the latter chiefly run to the contralateral superior olivary complex (SOC), whereas the neurones of the dorsal cochlear nucleus (DCN) terminate mainly in the central nucleus of the contralateral inferior colliculus (IC). The nerve cells of the superior olivary complex and nuclei of the lateral lemniscus (DLL, VLL) project to the IC. The IC neurones run mainly uncrossed to the medial geniculate body (MGB), i.e. the neurones of the central nucleus of the inferior colliculus terminate in the ventral nucleus of the medial geniculate body. This latter nucleus projects to the primary region A I of the auditory cortex, whereas the neurones in the pericentral medial geniculate body terminate in the associated auditory regions A II, EP and SF. The auditory areas of both hemispheres is well interconnected by commissural fibres. In addition to this ascending pathway there is a descending system. The parent cells correspond to pyramidal neurones in layer V in the auditory cortex. These neurones terminate in the medial geniculate body and in the pericentral nuclei of the inferior colliculus. From this, efferent neurones project to the DCN and SOC. The neurones of the olivocochlear bundles originate in the SOC; these bundles terminate predominantly on the surface of the outer hair cells in the organ of Corti.

Animals↗
PubMed2002

Branchial innervation.

Inspection of the dorsal end of fish gills reveals an impressive set of nerve trunks, connecting the gills to the brain. These trunks are branches of cranial nerves VII (the facial) and especially IX (the glossopharyngeal) and X (the vagus). The nerve trunks carry a variety of nervous pathways to and from the gills. A substantial fraction of the nerves running in the branchial trunks carry afferent (sensory) information from receptors within the gills. There are also efferent (motor) pathways, which control muscles within the gills, blood flow patterns and possibly secretory functions. Undertaking a more careful survey of the gills, it becomes evident that the arrangement of the microanatomy (particularly the blood vessels) and its innervation are strikingly complex. The complexity not only reflects the many functions of the gills but also illustrates that the control of blood flow patterns in the gills is of crucial importance in modifying the efficiency of its chief functions: gas transfer and salt balance. The "respiratory-osmoregulatory compromise" is maintained by minimizing the blood/water exchange (functional surface area of the gills) to a level where excessive water loss (marine teleosts) or gain (freshwater teleosts) is kept low while ensuring sufficient gas exchange. This review describes the arrangement and mechanisms of known nervous pathways, both afferent and efferent, of fish (notably teleosts) gills. Emphasis is placed primarily on the autonomic nervous system and mechanisms of blood flow control, together with an outline of the afferent (sensory) pathways of the gill arches.

Animals↗
PubMed2000

Reduced baroreflex sensitivity in elderly humans is not due to efferent autonomic dysfunction.

A progressive decline in baroreflex sensitivity (BRS) is a characteristic feature of human aging, the basis of which is poorly understood. The purpose of the present study was to determine whether alterations in efferent baroreflex function might contribute to the age-related decrease in BRS. We studied 10 healthy young (mean age 30.5 years; age range 22-40 years; six male) and 10 healthy elderly (mean age 70.7 years; age range 67-75 years; five male) volunteers. We tested efferent cardiac vagal function using the bradycardiac response to the cold face test, and efferent sympathetic function using heart rate and blood pressure responses to four stress tests: (i) low-level cognitive stress, (ii) high-level cognitive stress, (iii) hand immersion in ice water (cold pressor test) and (iv) isometric sustained hand-grip. Haemodynamic responses to these stresses are mediated via efferent baroreflex pathways, whereas the afferent components of each reflex response are independent of afferent baroreflex pathways. BRS was measured from simultaneous Finapres-derived continuous blood pressure and digital ECG R-R interval data using the sequence analysis paradigm. As expected, BRS was significantly reduced in the elderly group (7. 29+/-0.74 ms/mmHg; mean+/-S.E.M.) compared with the young group (13. 84+/-1.13 ms/mmHg; P<0.001). However, neither the bradycardiac responses to the cold face test nor the efferent sympathetically mediated heart rate/blood pressure responses to the stress test battery were significantly different between the young and elderly groups. We conclude that the age-related decrease in BRS is not attributable to impairments in the efferent sympathetic or parasympathetic system components of the baroreceptor reflex pathway.

Adult↗
PubMed1993

The central vagal efferent supply to the esophagus and lower esophageal sphincter of the cat.

BACKGROUND: Little is known of the central efferent neurons innervating the smooth muscle esophagus. The aim of this study was to define the location of the efferent neural pathways of the brain stem swallowing mechanism in the cat, particularly those supplying the esophageal body smooth muscle. METHODS: Fluorescent, retrogradely transported tracers were injected into the cervical striated muscle and thoracic smooth muscle segments of the esophagus and also the lower esophageal sphincter. RESULTS: Striated muscle efferents were found in the rostral nucleus ambiguus, but approximately 8% were located in the dorsal motor vagal nucleus. Smooth muscle efferents were present in the dorsal motor vagal nucleus in two groups, one rostral and one caudal to the obex. An additional group was found in nucleus retroambiguus. Approximately 8% of the total smooth muscle efferents were present in rostral nucleus ambiguus and were lateral to the striated muscle efferents. The lower esophageal sphincter efferents had a similar distribution to the smooth muscle efferents, but the rostral concentration of cells in the dorsal motor vagal nucleus was shifted caudally. CONCLUSIONS: Esophageal body smooth muscle motoneurons are arranged with a similar distribution to those innervating the lower esophageal sphincter but with some topographic variation.

Afferent Pathways↗
PubMed1997

Nucleus retroambiguus projections to lumbosacral motoneuronal cell groups in the male cat.

Recently, in the female cat, nucleus retroambiguus (NRA) projections have been described as distinct motoneuronal cell groups in the lumbar enlargement, possibly involved in lordosis behavior. The present study deals with the NRA-lumbosacral pathway in the male cat. Lumbosacral injections of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) were made to localize and quantify retrogradely labeled neurons in the caudal medulla. These injections were preceded by spinal hemisections to distinguish between neurons with ipsi- and contralaterally descending axons. The NRA-lumbosacral fibers descended almost exclusively contralaterally, but neurons in areas surrounding the NRA projected mainly ipsilaterally. Injections of WGA-HRP were made in the region of the NRA to determine its targets in the lumbosacral cord. To distinguish between the contralateral NRA pathways and the ipsilateral projections from neurons in the adjoining lateral tegmentum, the injections were preceded by ipsilateral hemisections in C2. A new scaling method was used to compare the results of the different cases, despite variations in size and segmental organization. The results show that the distribution pattern of anterogradely labeled fibers in the lumbosacral cord matched precisely the location of certain motoneuronal cell groups. The NRA projected densely to the abdominal wall and pelvic floor motoneurons in Onuf's nucleus, moderately to adductor longus, semimembranosus, and biceps femoris anterior motoneuronal cell groups, and only sparsely to iliopsoas and semitendinosus motoneuronal cell groups. Compared with the findings in the female, the NRA in the male cat projects more heavily to the biceps anterior and adductor longus and only sparsely to the iliopsoas and semitendinosus motoneuronal cell groups. These male-female differences are discussed.

Afferent Pathways↗
PubMed2000

Origins of cholinergic inputs to the cell bodies of intestinofugal neurons in the guinea pig distal colon.

Integration of function between gut regions is mediated by means of hormones and long neuronal reflex pathways. Intestinofugal neurons, which participate in one of these pathways, have cell bodies within the myenteric plexus and project their axons from the gut with the mesenteric nerves. They form excitatory synapses on neurons in prevertebral ganglia that in turn innervate other gut regions. The aim of the present study was to characterise immunohistochemically the synaptic input to intestinofugal neurons. The cell bodies of intestinofugal neurons that project from the distal colon were labelled with Fast Blue that was injected into the inferior mesenteric ganglia. Varicosities surrounding Fast Blue-labelled neurons were analysed for immunoreactivity for the vesicular acetylcholine transporter, vasoactive intestinal peptide, and bombesin. Most intestinofugal neurons were surrounded by nerve terminals immunoreactive for the vesicular acetylcholine transporter; many of these terminals also contained vasoactive intestinal peptide and bombesin immunoreactivity. This combination of markers occurs in axons of descending interneurons. Extrinsic denervation had no effect on the distribution of cholinergic terminals around intestinofugal neurons. A decrease in the number of vesicular acetylcholine transporter and vasoactive intestinal peptide immunoreactive terminals occurred around nerve cells immediately anal, but not oral, to myotomy operations. Consistent with previous physiological studies, it is concluded that intestinofugal neurons receive cholinergic synaptic input from other myenteric neurons, including cholinergic descending interneurons. Thus, intestinofugal neurons are second, or higher, order neurons in reflex pathways, although physiological data indicate that they also respond directly to distension of the gut wall.

Afferent Pathways↗
PubMed2003

Reevaluation of the primary motor cortex connections with the thalamus in primates.

Six injections (approximately 1 mm in diameter) of biotinylated dextran amine (BDA) were placed in different locations of the primary motor cortex of the rhesus monkey. Anterograde and retrograde labeling patterns in the thalamus were charted and individual labeled axons traced in continuous serial sections. Both anterograde and retrograde labeling in the thalamus was extensive, spanning several millimeters mediolaterally and including ventral lateral, ventral anterior, centromedian, and centrolateral nuclei. Paracentral, mediodorsal, lateral posterior, and medial pulvinar nuclei were also labeled. Two basic types of corticothalamic axons were identified: small to medium-width, type 1 axons that formed large terminal fields with small boutons, and thick, type 2 axons that formed small terminal fields with large boutons. Within each group, subtypes were identified based on specific features of the axons and terminals: two subtypes of type 1 axons and four subtypes of type 2 axons. The results revealed multiple modes of corticothalamic connectivity: sparsely distributed type 1 axons, dense plexuses of type 1 axons, type 2 axon terminal fields either singly or in clusters, and mixed plexuses of type 1 and type 2 axons. Only some cells in the plexuses were retrogradely labeled; some plexuses did not contain any labeled neurons, and many retrogradely labeled neurons were in the regions devoid of anterograde labeling. These connectivity patterns differed between thalamic nuclei. The results revealed much more complex relationships between M1 and thalamus than were previously thought to exist. It is suggested that this connectivity is neither of exclusively a feedback nature nor perfectly reciprocal but is subserved by a multitude of channels, most likely originating from different populations of cortical neurons, and feeding into a variety of functionally different neuronal networks, with each processing specific information.

Afferent Pathways↗
PubMed1977

Descending inputs to the octopus cell area of the cat cochlear nucleus: an electron microscopic study.

Large, unilateral lesions of the superior olivary complex (SOC) were made in 18 adult cats. Terminal degeneration was studied electron micrsocopically in the octopus cell area (OCA) of the caudal cochlear nuclei both ipsilateral and contralateral to lesions, after 1 to 14 postoperative days. Three synaptic types (OCA types 1, 2, and 3) have been previously described upon octopus cell somas and dendrites and types 1 and 2 identified as cochlear in origin. The present study shows a new synaptic ending (OCA type 4) on small octopus cell dendrites as well as dendrodendritic contacts. Following SOC ablations, type 4 endings degenerated in the OCA ipsilateral to the lesion. In the COA contralateral to the same lesion, however, degeneration was found in type 3 terminals ending upon more proximal octopus cell dendrities and upon somas. Ipsilateral terminal degeneration occurred between two and four postoperative days, was rare by seven days, and was gone by 14 days after these lesions. However, contralateral terminal degeneration was rare until four days, was most abundant after seven days, and was still present after 14 postoperative days. The different synaptic types and time courses of degeneration in the ipsilateral versus the contralateral OCA, suggested that type 4 endings originate from an ipsilateral source, such as the lesioned periolivary region, while type 3 endings originate from the contralateral SOC or from higher contralateral nuclei. Other evidence for these sources and possible functions of these descending inputs are briefly discussed.

Animals↗
PubMed1980

Pattern of development of ascending and descending fibers in embryonic spinal cord of chick: I. Role of position information.

Previous studies on the rigid time and position pattern of embryonic spinal cord development are extended to include the pattern of growth of axonal processes. This study was designed to analyze the position of axons in the marginal zone as they course (fasciculate) in the ascending and descending direction from a single spinal segment. Injections of 3H-proline were made into L1 or T6 of chick embryos of stages 21--29 (3.5--6 days of incubation). The location of radioactive label in the marginal zone was analyzed autoradiographically to show the location of labeled axons originating from the injected segment. In the early stages of development (stage 21), the labeled descending axons were located in the most ventromedial aspect of the marginal zone. The labeled ascending axons were located more laterally and to the perimeter of this zone. In stages 27--29, the labeled axons near the site of injection were located in the inner two-thirds of the marginal zone, and in the progressively more rostral levels the label shifted laterally and to the perimeter in a laminar pattern. It was concluded that the labeled ascending axons from an individual spinal segment layer upon the axons which originate from the more rostral segments. How this rigid time and position pattern of axonal growth can impart a topographic order into fiber tracts of the spinal cord was discussed.

Afferent Pathways↗
PubMed1980

Brain stem projections of sensory and motor components of the vagus complex in the cat: I. The cervical vagus and nodose ganglion.

The motor and sensory connections of the cervical vagus nerve and of its inferior ganglion (nodose ganglion) have been traced in the medulla oblongata of 32 adult cats with the neuroanatomical methods of horseradish peroxidase (HRP) histochemistry and amino acid autoradiography (ARG). In 14 of these subjects, an aqueous solution of HRP was applied unilaterally to the central end of the severed cervical vagus nerve. In 13 other cases, HRP was injected directly into the nodose ganglion. Three of these 13 subjects had undergone infranodose vagotomy 6 weeks prior to the HRP injection. A mixture of tritiated amino acid was injected into the nodose ganglion in five additional cats. The retrograde transport of HRP yielded reaction product in nerve fibers and perikarya of parasympathetic and somatic motoneurons in the medulla oblongata. Furthermore, a tetramethyl benzidine (TMB) method for visualizing HRP enabled the demonstration of anterograde and transganglionic transport, so that central sensory connections of the nodose ganglion and of the vagus nerve could also be traced. The central distribution of silver grain following injections of tritiated amino acids in the nodose ganglion corresponded closely with the distribution of sensory projections demonstrated with HRP, thus confirming the validity of HRP histochemistry as a method for tracing these projections. The histochemical and autoradiographic experiments showed that the vagus nerve enters the medulla from its lateral aspect in multiple fascicles and that it contains three major components--axons of preganglionic parasympathetic neurones, axons of skeletal motoneurons, and central processes of the sensory neurons in the nodose ganglion. Retrogradely labeled neurons were seen in the dorsal motor nucleus of X(dmnX), the nucleus ambiguus (nA), the nucleus retroambigualis (nRA), the nucleus dorsomedialis (ndm) and the spinal nucleus of the accessory nerve (nspA). The axons arising from motoneurons in the nA did not traverse the medulla directly laterally; rather, all of these axons were initially directed dorsomedially toward the dmnX, where they formed a hairpin loop and then accompanied the axons of dmnX neurons to their points of exit. Afferent fibers in the vagus nerve reached most of the subnuclei of the nTS bilaterally, with the more intense labeling being found on the ipsilateral side. Labeling of sensory vagal projections was also found in the area postrema of both sides and around neurons of the dmnX. These direct sensory projections terminating within the dmnX may provide an anatomical substrate for vagally mediated monosynpatic reflexes. Following deefferentiation by infranodose vagotomy 6 weeks prior to HRP injections into the nodose ganglion, a number of neurons in the dmnX were still intensely labeled with the HRP reaction product. The axons of these HRP-labeled perikarya may constitute the bulbar component of the accessory nerve.

Afferent Pathways↗
PubMed1982

Spinal cord development in anuran larvae: II. Ascending and descending pathways.

The ontogeny of ascending and descending spinal pathways was examined in bullfrog (Rana catesbeiana) tadpoles using the transported histochemical marker, horseradish peroxidase (HRP). The adult pattern of brainstem projections to lumbar spinal cord is evident as early as larval stage I (Taylor and Kollros, Anat. Rec., 94:7-24, 1946), although the number and size of projecting cells increases as the animal matures. These projections arise from presumptive hypothalamic neurons at the diencephalic-mesencephalic border as well as from neurons of the vestibular nucleus, oculomotor nucleus, and reticular formation. In contrast to the stability of the pattern of descending projections, the sources of fibers ascending to the brainstem change during larval life. In early larval stages, brainstem projections from lumbar spinal cord arise primarily from Rohon-Beard cells and neurons of the superficial dorsal horn. In later stages, neurons in the intermediate and ventral areas of the spinal gray can also be retrogradely labeled by HRP application to the brainstem at the level of the VIIIth nerve. Evidence of the existence of dorsal column and lateral cervical nuclei in adult frog and tadpoles older than stage VIII is presented. The ascending projections of embryonically born primary neurons were also investigated. Rohon-Beard cells, which are sensory neurons with their cell bodies in the spinal cord, were found to send ascending processes as least as far rostral as the level of the VIIIth nerve entry zone. Anterolateral and dorsal marginal cells, probable homologs, respectively, of mammalian spinal border cells and cells of Waldeyer (1888), were also found to project rostrally at least to the rhombencephalon. These marginal cells persisted through metamorphosis into adulthood.

Afferent Pathways↗
PubMed1984

Midbrain tegmental projections of nucleus reticularis thalami of cat and monkey: a retrograde transport and antidromic invasion study.

The projections of reticularis thalami (RE) neurons to midbrain reticular formation (MRF) and superior colliculus (SC) were studied in cat and monkey by using retrograde transport techniques and antidromic identification. The projections to MRF arise in rostral parts and lateral extent of RE nuclear complex whereas RE fibers to SC predominantly originate in the RE posteroventral district. Following injections of horseradish peroxidase (HRP) or fluorescent tracers into the MRF territory, retrogradely labeled neurons were always more numerous in the lateral hypothalamus and zona incerta than in the continuing RE wing. There were only very few doubly labeled RE cells following injections of fluorescent tracers into the midbrain tegmentum and thalamic nuclei, despite the fact that numerous doubly labeled cells occurred in the internal part of globus pallidum and pars reticulata of substantia nigra in the same animals. Control injections in the pons showed that RE labeling after midbrain injections was not due to uptake by fibers coursing more caudally. Antidromic identification experiments in cat confirmed the existence of a descending RE input to midbrain and further indicated that RE-midbrain projections consist of slow-conducting (congruent to 1 m/second) axons.

Afferent Pathways↗
PubMed1984

An HRP study of hypothalamo-cerebellar and cerebello-hypothalamic connections in squirrel monkey (Saimiri sciureus).

This study describes the distribution of labeled hypothalamic neurons in squirrel monkey following pressure injections of horseradish peroxidase (HRP) into cerebellar cortex and the pattern of labeling in the cerebellar nuclei subsequent to iontophoretic injections localized in the hypothalamus. Two types of HRP (HRP and a wheat germ agglutinin conjugate, HRP-WGA) were used as tracers; tetramethylbenzidine was the chromogen. Retrogradely filled neurons were found in lateral (LHAr) and posterior (PHAr) hypothalamic areas, and in the lateral mammillary (LMNu) and supramammillary (SMNu) nuclei following injections into ansiform and paramedian lobules and into the paraflocculus. Labeled cells were occasionally seen in the medial mammillary nucleus (parafloccular cases) and among fascicles of the mammillothalamic tract (all posterior lobe cases) immediately above the medial nucleus. After injections into the anterior lobe, labelling was again found in the LHAr, PHAr, LMNu, and SMNu. In addition, retrogradely filled cells were present in ventromedial, dorsomedial, and dorsal hypothalamic nuclei and in the dorsal hypothalamic area. Labeled cells were occasionally found among fascicles of the fornix along its intrahypothalamic course. In general, labeling extends into slightly more rostral hypothalamic levels in anterior lobe cases when compared to posterior lobe experiments. We interpret these data as indicating that some hypothalamic neurons project directly to the cerebellar cortex (i.e., hypothalamo-cerebellar fibers); this projection is bilateral with an ipsilateral preponderance. In experiments with injections of HRP-WGA into the cerebellar nuclei, anterogradely filled axons were traced into the contralateral PHAr and LHAr; this was suggestive of a direct cerebello-hypothalamic projection. Following iontophoretic injections localized in the LHAr and the medial mammillary nucleus, labeling was seen in the medial (NM), posterior interposed (NIP), and lateral (NL) cerebellar nuclei; this is essentially a contralateral projection. Retrogradely labeled cells were found in the rostral and ventral NM, the ventral and dorsocaudal NL, and diffusely throughout the NIP. On the basis of the known distribution of cerebello-thalamic fibers and other criteria, these labeled cells are representative of a true cerebello-hypothalamic projection. It is suggested that the cerebellum, through these pathways, may have a relatively direct influence on visceral centers in the brainstem and spinal cord.

Afferent Pathways↗
PubMed1986

Regional specialization in synaptic input and output in an identified local nonspiking interneuron of the crayfish revealed by light and electron microscopy.

Lateral inhibition of several mechanosensory interneurons in the crayfish terminal ganglion is mediated by a pair of identified local nonspiking interneurons called local directionally selective (LDS) interneurons. The ultrastructure and synaptic distribution of these interneurons were investigated by using intracellular labeling with horseradish peroxidase for electron microscopy. The LDS interneuron has bilateral, asymmetric arborizations. They are connected by a thick transverse neurite on which no synapses are made. The neurites on the side ipsilateral to the cell body are smooth and receive almost entirely input synapses. On the other hand, the contralateral neurites have prominent numerous swellings or varicosities from which many short fine spines arise, with intermingled input and output synapses. Both synapses, however, are not always associated with varicosities and spines. Presynaptic neurites of the LDS interneuron contain only round agranular synaptic vesicles in the vicinity of synaptic specializations. These morphological findings correlate well with the physiology of this interneuron: it is functionally polarized to receive input on one side (ipsilateral to the cell body) of the ganglion and convey it to the other side.

Afferent Pathways↗