Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Efferent Pathways”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1992

[Brain-stem auditory pathways: effects of atropine].

The efferent pathways exert a control action on the function of the cochlear nucleus and hair cells. Acetylcholine is the neurotransmitter of the centrifugal system and its action can be blocked by Atropine. In order to give a contribution to the knowledge of the function of the efferent bundle, Auditory Brainstem Responses (ABRs) and Acoustic Reflex Latencies (ARLs) have been examined in 10 young normal subjects there was also a decrease in latency greater than or equal to 100 microseconds by at least other two waves. The only statistically significant difference was relative to the latency mean value of the wave III recorded in contralateral derivation at 11 pps. The ARLs, after the infusion of atropine, showed a statistically significant increase in 7 of the 10 cases; no change was recorded in the AR amplitude. It can be concluded that the pharmacological block of the olivo-cochlear bundle determines a delay in the neural conduction of the acoustic impulses; this finding means that the atropine can inhibit the facilitating activity of the efferent system on the brainstem afferent pathways.

Acetylcholine↗
PubMed2004

Effects of hydrocephalus and ventriculoperitoneal shunt therapy on afferent and efferent connections in the feline sensorimotor cortex.

OBJECT: The authors of previous studies have suggested that connectivity within the cerebral cortex may be irreversibly altered by hydrocephalus. To examine connectivity-related changes directly, the authors conducted a study in which they used an axonal tracer in an animal model of infantile hydrocephalus. METHODS: In five hydrocephalic kittens low-pressure ventriculoperitoneal (VP) shunts were placed 10 to 14 days after induction of hydrocephalus by intracisternal kaolin injections. Wheat germ agglutinin-conjugated horseradish peroxidase was injected laterally into the motor cortex in hydrocephalic animals 9 to 15 days after kaolin injection, and 1, 2, and 4 weeks after VP shunt insertion in shunt-treated animals, and in age-matched controls. Reduction of antero- and retrograde labeling was most profound within the contralateral cortex and portions of the midbrain. Thalamic nuclei exhibited reductions in anterograde and retrograde labeling. Labeling within cell bodies of the ventral tegmental area decreased greatly in animals with untreated hydrocephalus, in which retrograde labeling was reduced in the locus coeruleus but did not affect the raphe nucleus. Shunt treatment increased both antero- and retrograde labeling of contralateral motor cortex to near-normal levels. Thalamic relay nuclei recovered antero- and retrograde labeling, although not to levels exhibited in controls. Shunt therapy restored cellular labeling within the ventral tegmental area and locus coeruleus. Recovery of labeling occurred as early as 7 days after shunt insertion. CONCLUSIONS: Collectively, analysis of these data indicates the following. 1) Cortical connectivity involving both afferent and efferent pathways was impaired in untreated hydrocephalic animals. 2) Shunt therapy improved both cortical afferent and efferent connectivity. 3) Complete reestablishment of the cortical efferent pathways, however, did not occur. Cortical pathway dysfunction, if permanent, could cause many of the motor and cognitive deficits seen clinically in children with hydrocephalus.

Afferent Pathways↗
PubMed1986

Reflex excitation and inhibition of the lower oesophageal sphincter induced by gastric distension in the cat.

Reflex responses of the lower oesophageal sphincter (l.o.s.) to distension of the stomach were studied by electromyographic and manometric techniques. Distension of the fundus and gastric antrum by inflation of a balloon elicited two types of reflex response of the l.o.s. Thus, whereas excitatory responses were recorded following slight distensions, larger distensions resulted in inhibitory responses. Splanchnic fibres and sympathetic fibres originating from the stellate ganglion, as well as vagal fibres served as the efferent pathways for the excitatory reflex response. The efferent pathways for the inhibitory response involved only vagal fibres.

Action Potentials↗
PubMed2000

[New approaches to the evaluation of functional state of afferent central nervous system pathways in patients with syringomyelia].

Functional state of both afferent and efferent pathways of CNS was studied with the method of magnetic stimulation (MS) in patients with syringomyelia. A control group contained 35 healthy individuals. The state of the efferent pathways was estimated by the time of the central motor conduction. The state of the afferent pathways of brain stem and spinal cord was analyzed by the latency of the motor responses of the orbicular muscle of the eye to MS of the spinal cord on the level of cervical and lumbar regions. The signs of the disorders in the conduction of the excitement through pyramidal pathways as well as through the afferent pathways of the spinal cord and the brain stem were registered in patients with syringomyelia. This observation allows to increase considerably the diagnostic range of MS.

Adult↗
PubMedDate not supplied

Contralateral suppression of transiently evoked otoacoustic emissions and neuro-otology.

Transiently evoked otoacoustic emissions can be suppressed with simultaneous contralateral sound stimulation. This is considered to be effected via the efferent pathway from the superior olivary complex (SOC) to the contralateral cochlea. This study examined this effect in patients with extrinsic and intrinsic lesions of the brainstem which may affect the efferent pathway either within the vestibular nerve which carries the efferent bundle to the cochlea or within the brainstem at the level of the SOC. Suppression is reduced or absent in these patients and the site and size of the lesion determines whether the suppression is affected unilaterally or bilaterally. Lesions affecting the auditory afferent pathway without significant alteration in hearing appear to affect the efferent pathway too.

Acoustic Stimulation↗
PubMed1992

Efferent neural pathways of the lamina terminalis subserving osmoregulation.

Studies in rats and sheep show that neurons in the CVOs of the lamina terminalis provide extensive neural input to the vasopressin-containing cells of the supraoptic nucleus. This input is both by direct pathways and via a synapse in the MnPO which also has projections to the vasopressin-containing cells of the SON. Neurons throughout the lamina terminalis (including possible osmoreceptors in the OVLT and subfornical organ) are activated by systematic hypertonicity. It is likely that in response to hypertonicity they signal the SON and PVN to release vasopressin and elsewhere to elicit other osmoregulatory responses such as thirst and the excretion of sodium.

Animals↗
PubMed2002

Further evidence that a shared efferent collicular pathway drives separate circuits for smooth eye movements and saccades.

The aim of the present study was to find out whether smooth eye movements (SEMs) evoked by superior colliculus (SC) stimulation are, as suggested by Breznen et al. (1996), artefactual eye movements resulting from a non-physiological response of the saccadic generator. This question was reinvestigated in head-restrained cats. Long-lasting SC stimulation was found to evoke, in a comparable proportion, either a single saccade followed by an uninterrupted SEM or a staircase of two or three saccades interleaved with SEMs. These two different patterns of eye movements could be elicited at a near-threshold current and at low stimulation frequencies. In most cases, SEM direction clearly differed from that of the preceding saccade. This difference between SEM and saccade directions varied in a systematic way as a function of the initial saccade direction. As demonstrated by computer simulation, this observation can be explained if the neural circuit controlling SEMs reaches a saturation level earlier than the saccadic burst-generator. Our results in cats were reminiscent of those reported by Breznen et al. (1996) in the monkey only in some instances, when high frequency stimulation (400-600 Hz) was applied. Indeed, in the case of near-threshold stimulation-elicited staircase saccades, increasing the stimulation frequency led to a progressive disappearance of the smaller subsequent saccades that were substituted by uninterrupted SEM-like movements. Altogether, the present results confirm the view that SEMs are genuine eye movements. These results rule out the hypothesis that SEMs result from a saturation of the saccadic generator and strengthen the hypothesis that SEMs and saccades are distinct movements. We suggest that the same collicular efferent cells carry out the motor command to saccadic and SEM circuits and that the position error originating from the SC may be distributed amongst separate downstream motor systems.

Animals↗
PubMed1999

A genetic approach to visualization of multisynaptic neural pathways using plant lectin transgene.

The wiring patterns among various types of neurons via specific synaptic connections are the basis of functional logic employed by the brain for information processing. This study introduces a powerful method of analyzing the neuronal connectivity patterns by delivering a tracer selectively to specific types of neurons while simultaneously transsynaptically labeling their target neurons. We developed a novel genetic approach introducing cDNA for a plant lectin, wheat germ agglutinin (WGA), as a transgene under the control of specific promoter elements. Using this method, we demonstrate three examples of visualization of specific transsynaptic neural pathways: the mouse cerebellar efferent pathways, the mouse olfactory pathways, and the Drosophila visual pathways. This strategy should greatly facilitate studies on the anatomical and functional organization of the developing and mature nervous system.

Animals↗
PubMed1994

Differential distribution of nitric oxide synthase in neural pathways to the urogenital organs (urethra, penis, urinary bladder) of the rat.

Axonal tracing techniques were used in combination with histochemical methods (NADPH-diaphorase activity and nitric oxide synthase immunoreactivity) to examine the distribution of nitric oxide synthase (NOS) in the neural pathways to the urogenital organs of the male rat. The major goal of this study was to compare the histochemical properties of the efferent and afferent neurons innervating the urethra with the properties of neurons innervating the penis and bladder. In the major pelvic ganglion (MPG) large percentages of postganglionic neurons innervating the urethra (44%) and the penis (97%) exhibited NADPH-diaphorase (NADPH-d) staining whereas only a small percentage (3.5%) of neurons innervating the bladder were N-d positive. Urethral neurons stained for N-d were on average smaller (33.3 microns diameter) than unstained neurons (54.5 microns diameter). The histochemical difference between the three types of neurons was also reflected in NOS-immunoreactivity (IR); however, the absolute percentage of neurons exhibiting NOS-IR was low: penis (21%), urethra (11%) and bladder (0%). Axonal varicosities staining for N-d or NOS-IR were noted in the MPG in close proximity to unidentified neurons and neurons innervating the urogenital organs. A considerable number of afferent neurons in the lumbosacral dorsal root ganglia (DRG) stained for N-d (64 cells/L6, 35 cells/S1 section); however, only small numbers of neurons (average 1 cell/section) exhibited NOS-IR. N-d activity was detected in a large percentage of urethral (55%) and bladder (80%) afferent neurons in the L6-S1 dorsal root ganglia (DRG) but in relatively few (12%) penile afferent neurons in the L6 ganglia. These results suggest that the contribution of nitric oxide (NO) to neurotransmission varies considerably in different urogenital organs. NO could have a significant role in postganglionic efferent pathways to the urethra and penis but very likely has no role in the efferent pathways to the bladder. Similarly, the prominence of N-d staining in some DRG neurons (e.g. urethra and bladder) but not others (penile) also raises the possibility of a varying role of NO in afferent pathways. However, in these neurons N-d staining was not paralleled by NOS-IR, which was present in only a small percentage of neurons. Thus, N-d staining may not reflect the presence of NO in afferent pathways to the pelvic viscera.

Afferent Pathways↗
PubMed1981

Hippocampal deafferentation and deefferentation and gastric pathology in rats.

Previous studies have shown that large hippocampal lesions increase the gastric pathology found in restrained and unrestrained animals. The present experiments investigated the effects of lesions in the two major afferent and efferent pathways of the hippocampus, i.e., the dorsal pathway through the fimbria-fornix and the ventral pathway in the entorhinal region, on gastric pathology in restrained and unrestrained rats. Result demonstrated that lesions in the ventral pathway produced an increased incidence of pathology whereas lesions in the fimbria-fornix did not. Neuroanatomical pathways which may mediate these effects are described

Afferent Pathways↗
PubMed1997

Autonomic nervous system and adrenergic receptors in chronic hypotensive haemodialysis patients.

BACKGROUND: The pathophysiology of chronic hypotension (CH) in uraemia is not elucidated. The possible role of autonomic nervous system dysfunction and adrenoceptor alterations in the pathophysiology of CH in uraemia was evaluated in this study. METHODS: Seventeen hypotensive haemodialysis (HD) patients, 17 normotensive HD patients, and 17 control subjects were studied. We evaluated the integrity of the baroreflex arc (Valsalva manoeuvre), the parasympathetic efferent pathway ('deep-breathing test') and the sympathetic efferent pathway ('hand-grip test'). We also evaluated platelet alpha 2-adrenoceptor and lymphocyte beta 2-adrenoceptor densities (radioligand binding assay), and beta 2-adrenoceptor response (intracellular cAMP generation after isoproterenol stimulation in lymphocytes). RESULTS: Responses to the Valsalva manoeuvre and the deep-breathing test were altered in all HD patients (P < 0.05). Valvalva ratio was lower in hypotensive patients than in normotensive patients (P < 0.01), whereas the pressor response to the hand-grip test was reduced only in hypotensive HD patients (P < 0.01). In haemodialysed patients, basal mean blood pressure (MBP) correlated with MBP increases during the hand-grip exercise (r = 0.59, P < 0.01). Plasma catecholamine levels were elevated in both groups of patients (P < 0.025). Plasma adrenaline levels were higher in hypotensive HD patients than in normotensive patients (P < 0.05). alpha 2- and beta 2-adrenoceptor densities and beta 2-adrenoceptor response were reduced in hypotensive patients (P < 0.05 vs normotensive patients). MBP correlated with alpha 2-adrenoceptor (r = 0.46, P < 0.01) and beta 2-adrenoceptor (r = 0.43, P < 0.025) densities in HD patients. CONCLUSIONS: Normotensive haemodialysed patients have increased plasma catecholamine levels with preserved alpha 2- and beta 2-adrenoceptor numbers, as well as beta 2-adrenoceptor responses. In hypotensive patients, plasma adrenaline levels were even higher; the increased plasma catecholamine levels induced an alpha 2- and beta 2-adrenoceptor downregulation. This downregulation may play a role in the reduced cardiovascular responses to adrenergic stimuli reported in hypotensive HD patients.

Adult↗
PubMed1992

Reconstruction of neural networks is organized by co-existence of various signal molecules or input activation in Helix pomatia L.

The overlapping neural networks consisting of multifunctional neurons were shown to take part alternatively in regulation of various visceral functions or behaviour. The reconstruction of the neural networks was shown to be a function of input activation or transmitter cocktail used at the vicinity of the neurons. In rearrangement of neural networks acetylcholine (Ach), serotonin (5HT) and molluscan neuropeptide, FMRFamide were found to be effective. The modulation occurs at the level of ion channels and at least three different types, namely the Ca-, delayed K- and the unspecific cation channels were shown to be responsible for it. The modulatory action of low molecular weight neurotransmitters and peptides was more often directed to the same species of ion channels, but the maximum of channel activation can appear at different voltage ranges. The modulation of afferent and efferent pathways by signal molecules can assure the mosaic-like functioning of the units of neural networks.

Acetylcholine↗
PubMed1976

The effects of irritation at various levels of the airway upon tracheal mucus secretion in the cat.

1. Sulphated glycoprotein output from the trachea, isolated in situ, has been measured in anaesthetized cats by a radio-isotopic method. The effects of irritation of various parts of the airway on this mucus output were studied. 2. Mechanical stimulation of the nose and nasopharynx increased tracheal mucus output by reflexes which involved parasympathetic and probably also sympathetic motor pathways. 3. Laryngeal stimulation had a similar through the same motor pathways. 4. Inhalation of ammonia vapour into the lower airways reflexly increased mucus output from the isolated trachea. The efferent pathway for this reflex was mainly or entirely parasympathetic. It is argued that the afferent pathway involved cough receptors. 5. Lung inflation, inhalation of histamine aerosol and intravenous injection of phenyl diguanide (which excite mainly lung stretch receptors, lung 'irritant' receptors and alveolar 'J-receptors' respectively) had no consistent effect on tracheal mucus secretion. 6. The afferent and efferent pathways of these reflexes are discussed.

Afferent Pathways↗
PubMed1988

Connections of a vagal communicating branch in the ferret. I. Pathways and cell body location.

In contrast to most other species, ferrets possess a single communicating branch connecting the dorsal and ventral vagal trunks immediately rostral to the diaphragm. This branch is being used in physiological studies of gastrointestinal function and emesis. However, the fibre routes which pass through this branch are not known. In this study, the afferent and efferent pathways within this supradiaphragmatic vagal communicating branch of the ferret were studied through the use of the horseradish peroxidase (HRP) tracing technique. The region of the branch was exposed using a thoracotomy and HRP crystals were applied to one of the following: (A) the ventral end of the communicating branch, (B) the dorsal end of the communicating branch, (C) the distal end of the dorsal vagal trunk rostral to the communicating branch or (D) the distal end of the ventral vagal trunk rostral to the communicating branch. Following a 72 hour survival period, the animals were reanaesthetized and perfused. The superior cervical and nodose ganglia and the brain stem were processed using the tetramethylbenzidine method. Following application of HRP to the cut ventral end of the communicating branch, labelled cell bodies were found in the left and right nodose ganglia and in the left dorsal motor nucleus of the vagus. After HRP application to the cut dorsal end of the communicating branch, labelled cells were found in the left and right nodose ganglia. No HRP containing cell bodies were found following HRP application to the cut distal end of either the dorsal or the ventral vagal trunk. These results indicate that several afferent pathways exist within the branch, although only one consistently labelled efferent pathway was found.

Afferent Pathways↗
PubMed1982

Effects of lesioning basal ganglia nuclei and output pathways on tremorine-induced tremor in rats.

The tremor produced by muscarinic cholinomimetics is believed to originate in the neostriatum but the efferent pathways are unknown. The intensity and frequency of tremor induced by tremorine was measured in the hindlegs of rats with unilateral basal ganglia lesions. A kainic acid lesion of one neostriatum reduced tremor intensity in the contralateral leg (CL). Unilateral electrolesions of the globus pallidus and nucleus accumbens had no effects on tremor. Both entopeduncular and subthalamic nuclei lesions reduced the frequency and intensity of tremorine tremor in the CL leg. The subthalamic lesion also increased tremor intensity and frequency in the ipsilateral leg. Lesions were made in some brain areas that receive basal ganglia efferent projections. Peak tremor intensity and frequency in both legs was greatly reduced by unilateral decortication. Unilateral lesions of the habenula, red nucleus and pedunculopontine nucleus had no effects on tremor intensity but reduced peak tremor frequency. Lesions of the substantia nigra and periaqueductal gray area had no effects on tremor. Unilateral removal of the superior colliculus reduced tremor intensity in both legs. The findings suggest that intensity and frequency of tremor are influenced by different basal ganglia efferent pathways; intensity involves strio-entopeduncular-cortical projections and frequency is determined by projections to midbrain and brainstem. The superior colliculus, with many muscarinic receptors, may be a direct target area for tremorine.

Animals↗
PubMed1992

High vocal center growth and its relation to neurogenesis, neuronal replacement and song acquisition in juvenile canaries.

It is generally thought that most circuits of the adult central nervous system (CNS) are sculpted, in part at least, by selective elimination of some of the neurons present in an initial overabundant set. In this scenario, the birth of neurons precedes the period when brain functions, such as learning, first occur. In contrast to this form of brain assembly, we describe here the delayed development of the high vocal center (HVC) and one of its efferent pathways in canaries. The retrograde tracer Fluoro-Gold (FG) was injected into one of HVC's two efferent targets, the nucleus robustus archistriatalis (RA), to define the boundaries of HVC. The HVC grows markedly between 1 and 4 months, invading neighboring territories of the caudal telencephalon. During this same period, 0.43%-0.64% of the HVC neurons present at 1 year of age are labeled per day of [3H]-thymidine injection. [3H]-Thymidine labeling is a marker of cell birth, and during the first 4 months HVC neuron number increases, probably accounting for part of the HVC growth observed. Thereafter, the number of HVC neurons remains constant, but neuronal birth persists. We infer from this that neuronal replacement starts as early as 4 months after hatching and perhaps before then. About half of the neurons born after posthatching day 10 grow an axon to RA to form the main efferent pathway exiting from HVC. HVC growth, neurogenesis, axogenesis, and the observed replacement of neurons happen during the period of juvenile vocal learning. However, the recruitment of neurons that are still present at 1 year shows no particular inflections corresponding to the various stages in song learning, and continues at essentially the same rate after the more stereotyped adult song has been acquired. We suggest that a combination of neurogenesis and neuronal replacement provides unique advantages for learning.

Animals↗
PubMed1993

Efferent signals of the suprachiasmatic nucleus.

It is well established that the mammalian suprachiasmatic nucleus (SCN) is a biological pacemaker that entrains the activity of organisms to their environment and controls circadian rhythmicity. However, neither the nature of these coupling signal or signals from the SCN, nor their target or targets in the brain, are well understood. Fiber efferents from the SCN reach nearby hypothalamic regions, suggesting a coupling role for neural efferent pathways. The SCN produces diffusible signals that reach nearby hypothalamic sites and the cerebrospinal fluid, suggesting a role for a diffusible efferent pathway. We consider the possibility of redundant coupling signals of the SCN, and review evidence suggesting that diffusible elements may be sufficient to sustain locomotor rhythmicity in adult animals and to restore locomotor rhythmicity in lesioned hamsters bearing SCN grafts. We also provide data for the occurrence of signals that synchronize oscillators, regardless of initial phase. The distinct role of neural and diffusible SCN coupling signals, and the role of SCN-driven rhythmic systems (pineal melatonin rhythms, body temperature), remain to be explored.

Animals↗
PubMed1994

[Autonomic dysfunction in chronic hypotension associated with uremia].

BACKGROUND: Chronic hypotension is a not uncommon complication among hemodialyzed patients which is responsible of an important morbidity. The autonomic nervous system (ANS) dysfunction seems to play a key role in the pathogenesis of chronic hypotension. METHODS: In order to study whether ANS dysfunction is responsible for chronic hypotension in hemodialyzed patients, the authors evaluated the integrity of the whole baroreflex arc by the Valsalva's manoeuver, of parasympathetic efferent pathway by the deep-breathing test and of sympathetic efferent pathway by the hand-grip test in 16 hemodialyzed patients with chronic hypotension, 17 normotensive hemodialyzed patients and 17 normal control subjects. Plasma catecholamine levels were also measured in these patients. RESULTS: In normotensive patients, Valsalva's manoeuver response (p < 0.005) and deep-breathing test response (p < 0.05) were lowered, while hand-grip test response was preserved. In chronic hypotensive patients, in addition to an impaired deep-breathing test (p < 0.05), a further reduced Valsalva's manoeuver response and a lower pressor response to hand-grip test were observed (p < 0.001). Catecholamine levels were higher in both groups of patients (p < 0.01) with respect to control subjects, specially in chronic hypotensive patients. CONCLUSIONS: In hemodialyzed patients (both normotensive and hypotensive) the whole baroreflex function and parasympathetic response are impaired. The lower pressor response to hand-grip test observed in hypotensive patients, in spite of the higher catecholamine levels, suggest that in these patients the cardiovascular dysfunction cannot be ascribed to a reduced sympathetic "outflow" but to a resistance of the target organs (heart and vessels) to the sympathetic stimulation.

Adult↗