Manual asymmetries and saccadic eye movements in right-handers during single and reciprocal aiming movements

The aim of the present study was to establish whether gracile afferents to the inferior olive are topographically organized and whether such inputs coincide with the location of cells that output to the hindlimb C1 zone in the cerebellar posterior lobe. Small injections (n=15) of the anterograde tracers Fluoro-Ruby or biotinylated dextran amine were made into gracile, resulting in anterograde labelling often distributed in partially separate, rostrocaudally directed columns within the lateral half of the contralateral rostral dorsal accessory olive (rDAO). In 12 cases, anterograde labelling was also located within the caudolateral medial accessory olive. Evidence for a topographical organization was obtained, suggesting that medial gracile targets only the most lateral part of rDAO, whereas lateral gracile also targets more medial parts. Gracile injections centred dorsally also resulted in more extensive terminal fields in rDAO than similar sized injections centred ventrally which may relate to the representation of the distal hindlimb in dorsal gracile (e.g., Millar and Basbaum, 1975). Injections of retrograde tracer (green beads) into the C1 zone in the ipsilateral caudal paramedian lobule (7 cases), resulted in retrograde cell labelling in the middle one-third of contralateral DAO in two columns that fused caudally. The proportion of labelled cells that overlapped with anterograde labelled terminals was related to the dorsoventral locus of the gracile injection site: gracile injections centred dorsally produced the largest degree of overlap and therefore, potentially, the greatest functional convergence. In summary, the results suggest that a topographical organization is present within the gracilo-olivo-cerebellar projection which is discussed in relation to the functional organization of the olivocerebellar system.     

Cells in and outside the motor trigeminal nucleus projecting to the cerebellar paramedian lobule

To investigate afferent projections to the cerebellar paramedian lobule (PML) from neurones in the motor trigeminal nucleus (Vmt) and the region around it, the method of retrograde transport of HRP, WGA-HRP and FG was employed in the rabbit. After tracer injection into various regions of PML, labelled neurones were observed mainly in the ventral and ventrolateral margins of the beta and gamma parts of Vmt, respectively. In the region just outside Vmt, neurones were labelled mainly in the lateral and dorsolateral parts of region 'h' and in the region adjacent to the root fibres of the facial nerve and even among them. Some neurones were recognized dorsally in region 'm' and in the pars alpha of the parvocellular reticular nucleus. The projection is sparse and bilateral with a slight ipsilateral predominance. Neurones in Vmt send axons to PML sublobules b-f. Projection from regions around Vmt reaches all PML sublobules with sublobules e-f receiving more fibres.     

Regionalization defects in the weaver mouse cerebellum

The mammalian cerebellum consists of parasagittal bands and transverse zones that are laid down early in development. When the adult cerebellum is immunostained for the Purkinje cell-specific antigen zebrin II (i.e., aldolase C), compartmentation is reflected in alternating zebrin II+ (P+) and zebrin II- bands (P ). The zebrin II phenotype is Purkinje cell autonomous; thus, disruptions in the zebrin pattern may reflect early problems in pattern formation. Zebrin II expression has been examined in the weaver (wv) mouse cerebellum. Both zebrin II- and zebrin II Purkinje cells are present in the homozygous weaver (wv/wv) mouse, but they are not distributed normally. In the posterior vermis, although the zebrin II+ bands are wider and multilaminate, the standard compartmentation is present. However, a large zebrin II+ cell mass is absent from the central vermis, and analysis of the anterior lobe reveals several missing zebrin II- bands. The cytoarchitectonic defects in wv mice are not simply related to the Purkinje cell abnormalities. Instead, serial reconstruction reveals two transverse boundaries-one rostrally in lobule VI and the other caudally in lobule IX-that delineate cytoarchitectonic transverse zones important in cerebellar development. The abnormal zebrin expression pattern in wv/wv mice may be secondary to the deletion of a transverse zone. This is the first demonstration that Purkinje cell compartmentation can be altered by mutation; therefore, the wv mutation should prove valuable in understanding cerebellar regionalization.     

Topographical organization of inferior olive cells projecting to translation and rotation zones in the vestibulocerebellum of pigeons

Previous electrophysiological studies in pigeons have shown that the vestibulocerebellum can be divided into two parasagittal zones based on responses to optic flow stimuli. The medial zone responds best to optic flow resulting from self-translation, whereas the lateral zone responds best to optic flow resulting from self-rotation. This information arrives from the retina via a projection from the accessory optic system to the medial column of the inferior olive. In this study we investigated inferior olive projections to translational and rotational zones of the vestibulocerebellum using the retrograde tracer cholera toxin subunit B. Extracellular recordings of Purkinje cell activity (complex spikes) in response to large-field visual stimuli were used to identify the injection sites. We found a distinct segregation of inferior olive cells projecting to translational and rotational zones of the vestibulocerebellum. Translation zone injections resulted in retrogradely labeled cells in the ventrolateral area of the medial column, whereas rotation zone injections resulted in retrogradely labeled cells in the dorsomedial region of the medial column. Motion of any object through space, including self-motion of organisms, can be described with reference to translation and rotation in three-dimensional space. Our results show that, in pigeons, the brainstem visual systems responsible for detecting optic flow are segregated into channels responsible for the analysis of translational and rotational optic flow in the inferior olive, which is only two synapses from the retina.     

Computer-aided studies on the spatial structure of the small hepatitis B surface protein

Progressive Multifocal Leukoencephalopathy (PML) is a subacute demyelinating opportunistic infection of the central nervous system which frequently occurs in AIDS. CT and MR, together with clinical and virological findings, can suggest a correct diagnosis in most cases, thus avoiding stereotactic biopsy which is too invasive considering the lack of therapy and the poor prognosis of this disease. In this study we reviewed the CT and MR findings of 16 proved AIDS-related PML cases. PML lesions appeared as hypodense on CT, hypointense on T1w, hyperintense on PDw and T2w MR images. CT was less sensitive than T2w MR images and underestimated the number of lesions and/or disease extent. On the basis of our findings during the progression of the lesions we observed two different patterns of PML presentation and evolution i.e., "single" and "multifocal". Single lesions generally involve subcortical white matter (arcuate fibers) of parietal lobe and spread to the contralateral hemisphere across the corpus callosum; multiple "patchy" lesions can be localized variably in the cerebral hemispheres and also in the brainstem and cerebellar hemispheres.     

Numerical aspects of pontine, lateral reticular, and inferior olivary projections to two paravermal cortical zones of the cat cerebellum

Two different olivo-cortico-nuclear zones in the cat cerebellum have been compared quantitatively as regards the numbers of cells projecting to them from within several sources of mossy fibres (MFs), namely the basal pontine nuclei (BPN), nucleus reticularis tegmenti pontis (NRTP), and the ipsilateral lateral reticular nucleus (LRN). The zones chosen were the C3 zone in lobule V of the anterior lobe and the C1 zone in pars copularis of the paramedian lobule (PMLpc), localised by recording climbing fibre-mediated potentials evoked on their surface as a result of volleys set up in their spino-olivocerebellar paths. The zones were injected with fluorescent-labelled latex microspheres and cell bodies, retrogradely labelled in the MF source nuclei and in the contralateral inferior olive, were counted and mapped. Evidence was obtained that tracer efficiency was very high in both the MF projections and the olivo-cerebellar projection and that each olivocerebellar axon may provide only one climbing fibre to the upper part of a lobule V folium but an average of nearly two to the same part of a PML folium. When the numbers of labelled cells in each MF source nucleus were expressed as a percentage of the total number of labelled pontine cells, the biggest source for lobule V was the contralateral BPN, followed by LRN, contralateral NRTP, ipsilateral BPN, and ipsilateral NRTP. For PMLpc, the order was similar except that ipsilateral BPNs exceeded contralateral NRTPs, but the dominance of contralateral BPN as a source was much greater. Cell totals were converted into projection densities (i.e., numbers of cells labelled per square millimetre of cortical sheet involved in the injection site); densities for PMLpc were found to be almost three times greater than those for lobule V for contralateral BPN but the two densities were not significantly different for ipsilateral BPN. The three other MF sources projected at higher densities to lobule V than to PML. These findings indicate that two cortical zones, both of which receive climbing fibres from the rostral part of the dorsal accessory olive and project to nucleus interpositus anterior, nevertheless differ markedly in regard to both the relative and the absolute sizes of the projections they receive from several of their most important sources of MFs.     

Placental peroxidase--further purification of the enzyme and oxidation of thiobenzamide

Non-Immunoglobulin Salivary Agglutinins (NIA) which directly bind to microbes [including HIV] were studied for their potential to activate the first complement component (C1). It was determined that NIA had the same specific activity as heat aggregated IgG in binding to C1q and in activating C1. In order to determine the region of C1q which bound to NIA, C1q globular heads and C1q stems (collagen-like regions) were prepared and separated via a Western blot procedure. NIA bound principally to the globular heads of C1q and weakly to the collagen-like stem region. NIA were also studied for their potential to activate native C1 in normal human serum. Heat-aggregated IgG and cardiolipin served as positive controls. It was observed that incubation of isolated NIA with fresh normal human serum resulted in the formation of sodium dodecyl sulfate (SDS)-irreversible complexes of activated C1r-C1 inhibitor and activated C1s-C1 inhibitor and in activated C1s mediated C4 conversion. This indicated that isolated NIA had the potential to directly and effectively mediate classical complement pathway activation. Preincubation of NIA with C1q, blocked NIA mediated C1r and C1s activation and C4 conversion. The concn of NIA required to activate C1r and C1s was similar to that of heat-aggregated human IgG. In kinetic ELISA, NIA or aggregated IgG (positive controls) were first immobilized on microtiter plates, blocked with gelatin then incubated with fresh human serum as a source of complement. Depositions of C4b, C3b and iC3b substantiated that the complement system was effectively activated by immobilized NIA. The optimal relative NaCl concn for C4b deposition was 0.11 M. While pre-incubation of NIA with C1q blocked the subsequent C1 fixing potential of NIA, pre-incubation of NIA with rgp160 [HIV-1] or fibronectin did not interfere with the potential of NIA to fix C1.     

The cortico-related zones of the rabbit claustrum-study of the claustrocortical connections based on the retrograde axonal transport of fluorescent tracers

The claustrocortical connections in the rabbit were assessed for the first time by the method of axonal retrograde transport of two fluorescent tracers (Fast Blue and Diamidino Yellow). The material consisted of 23 adult New Zealand rabbits. Projection zones of spindle-like form, connected with the precentral, postcentral, temporal and occipital cortices have been delineated. They are organized topographically both in the anteroposterior and ventrodorsal direction. The precentral (motor) projection zone is localized in the anterodorsal part of the claustrum. It may be divided into two separate parts that project to the medial and lateral part of the precentral cortex. The large postcentral (somatosensory) zone occupies mainly the central part, whereas the temporal (auditory) and occipital (visual) zones are situated in the posteroventral part of the claustrum. The overlap of various claustral projection zones is differentiated, the largest being that of the somatosensory zones. In comparison to the results of study of claustral projection zones performed on other species, presumably on the rat and cat, its seems plausible to conclude that the extension of claustral projection zones and degree of their overlap in the rabbit represent an intermediate character.     

Evaluation of the medial soft-tissue restraints of the extensor mechanism of the knee

We performed an anatomical dissection of the medial soft-tissue retinacular fibers that restrain lateral patellar displacement and found that the medial patellofemoral ligament inserts not only on the patella but also on the undersurface of the distal aspect of the quadriceps mechanism. The deep capsular layer contained substantial retinacular fibers that were associated with the medial patellomeniscal ligament. Functional studies of the relative contributions of the medial soft-tissue restraints in the prevention of lateral patellar displacement were also performed. Twenty-five fresh-frozen specimens of the knee, obtained after amputations (nineteen specimens) or from cadavera (six specimens) were tested biomechanically on a universal testing instrument. We ranked the soft-tissue restraints, in order of their relative contributions to the restraining force, on the basis of the percentage of force provided by the retinacular and ligamentous tissue that resisted the lateral displacement of the patella. The medial patellofemoral ligament, although varying in size and importance, was found to be the major medial soft-tissue restraint that prevented lateral displacement of the distal knee-extensor mechanism, contributing an average of 53 per cent of the total force. The patellomeniscal ligament and associated retinacular fibers in the deep capsular layer of the knee, which were previously thought to be functionally unimportant in the stabilization of the patella, contributed an average of 22 per cent of the total force. The previously described retinacular fibers (the patellotibial band) were functionally unimportant in the prevention of lateral displacement.     

Ultrastructure of collagen thermally denatured by microsecond domain pulsed carbon dioxide laser

BACKGROUND: Clinical improvement in photodamaged skin after carbon dioxide (CO2) laser resurfacing is thought to result in part from thermal collagen shrinkage. The presence of such collagen has not been unequivocally demonstrated. To identify and characterize the morphological features of collagen after CO2 laser exposure, we irradiated ex vivo human facial skin and bovine calcaneus tendon with microsecond domain pulsed CO2 laser energy and examined specimens for histopathological and ultrastructural changes in collagen. OBSERVATIONS: In dermis and tendon, 3 zones of collagen structure were apparent on electron microscopy. The first, most superficial zone demonstrated loss of collagen structure. The second zone consisted of admixed normal collagen fibers and thickened collagen fibers. Zone 3 consisted of normal-appearing collagen fibers. CONCLUSIONS: Ultrastructural examination of irradiated collagen revealed distinct morphological zones of denatured collagen fibers. Partially denatured fibers had an increased diameter consistent with lineal shrinkage. Zonal distinction was undetectable by light microscopy. Ultrastructurally, the zones of denatured collagen located above the normal fibers correlated with the zone of altered material seen on light microscopy. These findings suggest that collagen fiber shrinkage does occur after pulsed CO2 laser irradiation and that this phenomenon contributed, at least in part, to the immediate tissue contraction observed clinically.     

Classical conditioning of the rabbit eyelid response with a mossy-fiber stimulation CS: I. Pontine nuclei and middle cerebellar peduncle stimulation.

The nictitating membrane/eyelid responses of 18 rabbits were classically conditioned using cerebellar mossy-fiber stimulation as a conditioned stimulus (CS) and air puff as an unconditioned stimulus (US). The dorsolateral, lateral, and medial pontine nuclei and the middle cerebellar penduncle were effective stimulation-CS sites for training. In one group of rabbits, robust conditioned eyelid responses were produced with paired trials and subsequently extinguished with CS-alone and explicitly unpaired presentation of the CS and US. In a second group of rabbits, no conditioned responses were evident for 4 days of unpaired CS and US presentations. Conditioned responses did develop, however, after paired training was begun. Lesions of the interpositus nucleus of the cerebellum completely abolished the conditioned responses of a third group of rabbits overtrained with the mossy-fiber CS and air-puff US. Results support studies that have demonstrated that the cerebellum is critically involved in acquisition and retention of simple learned responses and theories of cerebellar function which have proposed that mossy fibers supply critical "learning" input to the cerebellum for acquisition and retention of motor skills. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple knife cuts between the medial and lateral hypothalamus in the rat: A reevaluation of hypothalamic feeding circuitry.

In 2 experiments single or multiple sets of bilateral knife cuts were made in a total of 73 female CFE rats just lateral to the ventromedial hypothalamus (VMH) and/or just medial to the lateral hypothalmus (LH). The lateral VMH knife cuts by themselves produced greater hyperphagia and obesity than did the medial LH cuts. The lateral VMH knife cuts also significantly increased food intake and body weight in Ss previously given bilateral cuts along the medial LH border. Findings indicate that the feeding inhibitory fibers responsible for the hyperphagia syndrome do not project from the VMH to the LH, and this calls for a reevaluation of hypothalamic circuitry. It was also discovered that sham surgery in 7 Ss had a significant suppressive effect on the hyperphagia syndrome produced by hypothalamic knife cuts. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transformation of peripheral inputs by the first-order lateral line brainstem nucleus

Extracellular recording techniques were used to record the responses of medial nucleus cells and posterior lateral line nerve fibers in mottled sculpin, Cottus bairdi, and goldfish, Carassius auratus, to a 50-Hz dipole source (vibrating sphere). Responses were characterized in terms of (1) receptive fields that relate responsiveness (spike rate and phase-locking) to the location of the source along the length of the fish, (2) input-output functions that relate responsiveness to vibration amplitude for a fixed source location, and (3) peri-stimulus time histograms that relate responsiveness to time during a sustained period of vibration. Relative to posterior lateral line nerve fibers, medial nucleus cells in both species were similar in showing (1) lower spontaneous and evoked rates of spike activity, (2) greater degrees of adaptation, (3) greater heterogeneity in all response characteristics, and (4) evidence for inhibitory/excitatory interactions. Whereas receptive fields of nerve fibers in both species faithfully reflect both pressure gradient amplitudes (with rate changes) and directions (with phase-angle changes) in the stimulus field, receptive fields of medial nucleus were more difficult to relate to the stimulus field, Some, but not all, receptive fields could be modeled with excitatory center/inhibitory surround and inhibitory center/excitatory surround organizations.     

Stimulation of the lateral septum is a more effective conditioned stimulus than stimulation of the medial septum during classical conditioning of the eye-blink response.

Eight rabbits were trained in the classically conditioned eye-blink response procedure using stimulation of the septal nuclei as the conditioned stimulus (CS). Each rabbit was trained with both medial septal stimulation and lateral septal stimulation. Stimulation of the medial septum was a far less effective CS than stimulation of the lateral septum. This effect may be due to the different roles of these two nuclei in classical conditioning. Conditioning using lateral septal stimulation as a CS is dependent on the cerebellar interpositus nucleus as is conditioning using peripheral and other brain stimulation CSs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The fine structure of the hypothalamic secretory neurons of the white-crowned sparrow, Zonotrichia leucophrys gambelii (Passeriformes: Fringillidae). II. Magnocellular and parvocellular nuclei of the rostral hypothalamus

The fine structures of the neurons and neuropils of the magnocellular supraoptic nucleus and the parvocellular nuclei of the rostral hypothalamus, including the suprachiasmatic and medial, lateral and periventricular preoptic nuclei, and the neuronal apparatus of the organum vasculosum laminae terminalis, have been examined in the male White-crowned Sparrow, Zonotrichia leucophrys gambelii, by correlated light and electron microscopy. The magnocellular supraoptic nucleus is characterized by large neurosecretory perikarya which contain a well developed Golgi complex and dense-cored granules 1,500-2,200 A in diameter. The neuropil displays axons, dendrites and glial fibers. Some axonal profiles contain dense-cored vesicles 800-1,000 A in diameter and clear vesicles 500 A in diameter. Axo-somatic and axo-dendritic synapses are conspicuous in this nuclear region. The suprachiasmatic nucleus is characterized by an accumulation of small neurons with moderately developed cellular organelles and some dense-cored granules, approximately 1,000 A in diameter. The profiles of axons within the neuropil contain dense-cored granules 800-1,000 A in diameter and clear vesicles 500 A in diameter. The neurons of the medial preoptic nucleus are relatively large and exhibit well developed cellular organelles and dense-cored granules 1,300 to 1,500 A in diameter. Granular materials are formed within the Golgi complex. The medial preoptic nucleus is rich in secretory perikarya. Occasionally, neurons with granules 1,500-2,200 A in diameter are encountered in the lateral preoptic and periventricular preoptic nuclei. They may be considered as scattered elements of the magnocellular (supraoptic and paraventricular) system. The organum vasculosum laminae terminalis consists of three layers, i.e., ependymal, internal and external zones, and exhibits a vascular arrangement similar to that of the median eminence. The perikarya of the parvocellular neurons and their axons in the internal zone contain numerous secretory granules ranging from 1,300 to 1,500 A in diameter.     

Regional intramuscular pressure development and fatigue in the canine gastrocnemius muscle in situ

Intramuscular pressure (PIM) was measured simultaneously in zones of the medial head of the gastrocnemius-plantaris muscle group (zone I, popliteal origin; zone II, central; zone III, near calcaneus tendon) to determine regional muscle mechanics during isometric tetanic contractions. Peak PIM averages were 586, 1,676, and 993 mmHg deep in zones I, II, and III and 170, 371, and 351 mmHg superficially in zones I, II, and III, respectively. During fatigue, loss of PIM across zones was greatest in zone III (-81%) and least in zone I (-60%) when whole muscle tension loss was -49%. Recovery of PIM was greatest in zone III and least in zone II, achieving 86% and 67% of initial PIM, respectively, when tension recovered to 89%. These data demonstrate that 1) regional mechanical performance can be measured as PIM within a whole muscle, 2) PIM is nonuniform within the canine gastrocnemius-plantaris muscle, being greatest in the deep central zone, and 3) fatigue and recovery of PIM are dissimilar across regions. These differences suggest distinct local effects that integrate to determine whole muscle mechanical capacity during and after intense exercise.     

Use of embryonal stem cells in studies of molecular haemopoiesis

We have examined the morphology of afferent endings that originate in three distinct cell groups and terminate in the lateral posterior nucleus of the thalamus (LP). Retino-LP projections were sparse, occurred throughout the nucleus, and could be classified into 1) simple en passant varicosities and terminal swellings found on poorly branched fibers in all LP subdivisions, 2) string-like configurations of varicosities detected largely in the medial subdivision of the LP, and 3) terminals resembling retinogeniculate endings occurring mainly in the rostral part of the superficial subdivision of the LP adjacent to the dorsal nucleus of the lateral geniculate body. Cortico-LP terminals fell into three classes: 1) single varicosities decorating the tips of short appendages on fine preterminal and terminal axons; 2) tiny, round varicosities studding the axon shaft; and 3) boutons of variable shape visible on medium-caliber corticothalamic fibers. Tecto-LP terminals exhibited a large variation in morphology and density. Those found most commonly could be classified into two groups: 1) individual swellings and 2) terminal clusters arranged in a tubular configuration that enclosed a central channel, most likely occupied by the dendrite of a postsynaptic neuron. An unusual tecto-LP terminal consisted of an ovoid swelling (up to 20 microns in the long axis) from which emerged several long, thin extensions and was seen at the tips of large-diameter axons. These results show that, despite having overlapping projection zones, each set of afferents that projects to the LP elaborates terminal specializations that are structurally distinct from others projecting to the same target area.     

Extracellular matrix organization in various regions of rat brain grey matter

Previous studies revealed the concentration of extracellular matrix proteoglycans in the so-called perineuronal nets on the one hand and in certain zones of the neuropil on the other. This nonhomogeneous distribution suggested a non-random chemical and spatial heterogeneity of the extracellular space. In the present investigation, regions dominated by one of both distribution patterns, i.e. piriform and parietal cortex, reticular thalamic nucleus, medial septum/diagonal band complex and cerebellar nuclei, were selected for correlative light and electron microscopic analysis. The labelling was performed by the use of the N-acetylgalactosamine-binding plant lectin Wisteria floribunda agglutinin visualized by peroxidase staining and additionally by photoconversion of red carbocyanine fluorescence labelling for electron microscopy. The intense labelling of the neuropil of a superficial piriform region, presumably identical with sublayer Ia, was confined to a fine meshwork spreading over the extracellular space between non-myelinated axons, dendrites and glial profiles. In the reticular thalamic nucleus the neuronal cell bodies were embedded in zones of labelled neuropil. In contrast to these patterns, the labelled extracellular matrix in different cortical layers and in the other subcortical regions was concentrated in perineuronal nets as large accumulations at surface areas of the neuronal perikarya and dendrites and the attached presynaptic boutons. Astrocytic processes usually were separated from the neuronal surface by the interposed extracellular material. Despite a great variability, the width of the extracellular space containing the labelled matrix components in all perineuronal nets appeared to be considerably larger than that in the labelled zones of neuropil and the non-labelled microenvironment of other neurons. Our results support the view that differences expressed in topographical and spatial peculiarities of the extracellular matrix constituents are related to neuron-type and system-specific functional properties.     

Efferent sympathetic and vagal innervation of the canine right ventricle

BACKGROUND: The functional pathways of efferent sympathetic and vagal innervation to the right ventricle (RV) might be important in a variety of disease states that involve the RV wall. The purpose of this study was to investigate those pathways. METHODS AND RESULTS: We determined the effects of phenol and endocardial radiofrequency ablation applied to the RV anterolateral wall and outflow tract on effective refractory period (EPR) shortening during bilateral ansae subclaviae stimulation and ERP lengthening during bilateral vagal stimulation. We found that efferent sympathetic axons to the RV are located in the superficial subepicardium and that lateral sites receive sympathetic innervation predominantly from the lateral margin of the RV near the AV groove. Medial sites close to the left anterior descending coronary artery (LAD) receive sympathetic innervation from both the right lateral atrioventricular (AV) groove and regions near the LAD. At the RV outflow tract, some sympathetic fibers are located intramurally. Efferent vagal fibers are located at the RV surface within 10 mm of the right lateral AV groove; they penetrate intramurally and reach to the medial sites of the RV anterior wall. Other vagal fibers originate near the LAD and are intramural. Vagal fibers to the RV outflow tract are located intramurally either from the lateral side (close to the right coronary artery) or medial side (close to the LAD). CONCLUSIONS: Efferent vagal and sympathetic innervation of the right ventricle resembles that of the left ventricle. A major difference is that efferent sympathetic fibers to the right ventricular outflow tract are located not only in the subepicardium but in the subendocardium as well.