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 109 records · Page 6Linked to original sources
PubMed1986

Neuroanatomy, neurophysiology, and central auditory assessment. Part III: Corpus callosum and efferent pathways.

In this, the last of a three-part series on neuroanatomy/physiology related to central auditory assessment, two topics will be presented: the corpus callosum and the efferent auditory system. A general anatomical description of the corpus callosum is followed by information on the topographical representation of the cortex within the corpus callosum. Auditory areas of the corpus callosum and the transcallosal auditory pathway are emphasized. Data on transfer time across the corpus callosum and the possible role of inhibitory and excitatory fibers of this commissure are presented. Neuropsychological studies relative to neuroanatomy/physiology of the corpus callosum are discussed, and the efferent auditory system from cortex to cochlea is described. Emphasis is placed on the structure and function of the olivocochlear bundle along with some clinical relationships to probable disorders of the descending pathway of the caudal brain stem.

Agenesis of Corpus Callosum↗
PubMed1976

Axonal transport in the efferent pathways of the hippocampus: labeling of projection areas after (3H)valine injections.

[3H]Valine was injected into the medial and lateral CAI of the dorsal hippocampus and the radioactivity accumulated in areas of some of its efferent projections was measured by scintillation counting. The labeling of the septum, thalamus, hypothalamus, corpus mammillare, preoptic area and basal telencephalon significantly exceeded the corresponding background activities. Fimbria transection before [3H]valine injection reduced the labeling of these areas to background levels. Differences were observed between medial and more lateral CAI injection sites in the distribution of 3H label among projection areas. The dynamics of axonal transport were studied in 4 of these projection areas: septum, thalamus, hypothalamus and corpus mammillare. A rapidly moving wave of radioactivity began to arrive in all areas 1--3 h after injection. The rate was roughly estimated to be around 100 mm/day in the fibers projecting to the corpus mammillare after injections into the medial CAI. When the brain areas were fractionated into crude nuclear, mitochondrial-synaptosomal and microsomal fractions, projection areas were found to contain more label per milligram of protein in the mitochondrial-synaptosomal fraction than control areas.

Animals↗
PubMed1993

Effects of damage to SCN neurons and efferent pathways on circadian activity rhythms of hamsters.

This experiment was designed to determine if entrainment to a light:dark (LD) schedule and the free-running rhythm in constant light are altered by partial lesions of suprachiasmatic nuclei (SCN) cells or SCN output pathways. Twenty-four male golden hamsters were housed under 12L:12D. Hamsters received either lesions (n = 16), sham surgery (n = 4), or no surgery (n = 4), and were placed into individual cages with running wheels under 14L:10D. Each time after 4 weeks, the LD schedule was phase advanced by 6 h, phase delayed by 6 h, and then the animals were exposed to constant dim light. At the end of the experiment, brain sections were processed for peptide histidine isoleucine (PHI) and gastrin releasing peptide (GRP) immunohistochemistry. Alternate sections were stained for cells and fibers. Behavioral results indicate that (a) very few SCN cells and SCN efferent fibers, as labeled by PHI and GRP immunohistochemistry, are necessary for the expression of circadian rhythmicity in wheel running, and (b) damage to pathways rostral to the SCN may be more critical for entrainment and rhythmicity than damage to caudal pathways. Targets of PHI- and GRP-immunoreactive SCN efferent fibers were also identified.

Animals↗
PubMed1996

Efferent pathways of the nucleus of the optic tract in monkey and their role in eye movements.

To clarify the role of the pretectal nucleus of the optic tract (NOT) in ocular following, we traced NOT efferents with tritiated leucine in the monkey and identified the cell groups they targeted. Strong local projections from the NOT were demonstrated to the superior colliculus and the dorsal terminal nucleus bilaterally and to the contralateral NOT. The contralateral oculomotor complex, including motoneurons (C-group) and subdivisions of the Edinger-Westphal complex, including motoneurons (C-group) and subdivisions of the Edinger-Westphal complex, also received inputs. NOT efferents terminated in all accessory optic nuclei (AON) ipsilaterally; contralateral AON projections arose from the pretectal olivary nucleus embedded in the NOT. Descending pathways contacted precerebellar nuclei: the dorsolateral and dorsomedial pontine nuclei, the nucleus reticularis tegmenti pontis, and the inferior olive. Direct projections from NOT to the ipsilateral nucleus prepositus hypoglossi (ppH) appeared to be weak, but retrograde tracer injections into rostral ppH verified this projection; furthermore, the injections demonstrated that AON efferents also enter this area. Efferents from the NOT also targeted ascending reticular networks from the pedunculopontine tegmental nucleus and the locus coeruleus. Rostrally, NOT projections included the magnocellular layers of the lateral geniculate nucleus (lgn); the pregeniculate, peripeduncular, and thalamic reticular nuclei; and the pulvinar, the zona incerta, the mesencephalic reticular formation, the intralaminar thalamic nuclei, and the hypothalamus. The NOT could generate optokinetic nystagmus through projections to the AON, the ppH, and the precerebellar nuclei. However, NOT also projects to structures controlling saccades, ocular pursuit, the near response, lgn motion sensitivity, visual attention, vigilance, and gain modification of the vestibulo-ocular reflex. Any hypothesis on the function of NOT must take into account its connectivity to all of these visuomotor structures.

Afferent Pathways↗
PubMed1975

The origin of efferent pathways from the primary visual cortex, area 17, of the macaque monkey as shown by retrograde transport of horseradish peroxidase.

The retrograde transport of horseradish peroxidase has been used to identify efferent cells in area 17 of the macaque. Cells projecting to the lateral geniculate nucleus are small to medium sized pyramidal neurons with somata in lamina 6 and the adjacent white matter. The projection to the parvocellular division arises preferentially from the upper half of lamina 6, while that to the magnocellular division arises preferentially from the lower part of the lamina. The projection to both superior colliculus and inferior pulvinar arises from all sizes of pyramidal neurons lying in lamina 58 (Lund and Boothe, '75); at least pyramidal neurons of lamina 5B send collateral axon branches to both destinations. Injections with extensive spread of horseradish peroxidase show that many cells of lamina 4B and the large pyramidal neurons of upper lamina 6 also project extrinsically but their terminal sites have not been identified. Other studies have indicated that cells of laminae 2 and 3 project to areas 18 and 19. Therefore every lamina of the visual cortex, with the exception of those receiving a direct thalamic input, contains cells projecting extrinsically. Further, each lamina projects to a different destination and from Golgi studies can be shown to contain cells with specific patterns of dendritic branching which relate to the distribution of thalamic afferents and to the patterns of intracortical connections. These findings emphasise the significance of the horizontal organisation of the cortex with relation to the flow of information through it and contrast with the current concept of columnar organisation shown in physiological studies.

Animals↗
PubMed1990

Metabolic activation of efferent pathways from the rat area postrema.

We used the quantitative [14C]deoxyglucose method and autoradiography to evaluate metabolic activity in 47 individual cerebral structures or subregions that are part of neural pathways emanating from the brain stem circumventricular organ, area postrema. Electrical stimulation of the dorsocentral area postrema in halothane-ventilated rats produced hypotension and increased glucose metabolism by several structures within the ascending trajectories of efferent neural projections from the nucleus. Structures in the caudal medulla oblongata, including three subnuclei of the nucleus of the solitary tract, dorsal motor nucleus of the vagus nerve, and nucleus ambiguus-A1 noradrenergic region, had increases of metabolism during stimulation of 32-62%. Pontine activation occurred specifically in the locus coeruleus and lateral parabrachial nuclei (increases of 24-36%). Magnocellular and parvocellular subdivisions of the hypothalamic paraventricular nucleus, supraoptic and suprachiasmatic nuclei, and median eminence showed increases in metabolism of 22-34%. An 89% elevation of glucose metabolism by the pituitary neural lobe resulted. The findings are evidence for functional activation of specific structures within ascending neural pathways from area postrema to forebrain mechanisms regulating blood pressure and fluid balance.

Animals↗
PubMed1977

[Use of local electromyography for revealing conductivity along efferent pathways in patients with traumatic lesions of the spinal cord ].

Electrical activity of the gastrocnemius and of the tibial muscles were examined in the patients with the spinal cord trauma during the active strain to extend or to flex the foot; action potentials of the motor units (MU) were recorded in a number of these patients during the mentioned volumtary efforts, despite the absence of interference electromyogram (EMG). A voluntary MU activation led to the conclusion on a possibility of detection by the local EMG method of the efferent conductivity partially persisting after the trauma along the spinal cord route.

Electromyography↗
PubMed2004

Orexin neurons function in an efferent pathway of a food-entrainable circadian oscillator in eliciting food-anticipatory activity and wakefulness.

Temporal restriction of feeding can entrain circadian behavioral and physiological rhythms in mammals. Considering the critical functions of the hypothalamic orexin (hypocretin) neuropeptides in promoting wakefulness and locomotor activity, we examined the role of orexin neurons in the adaptation to restricted feeding. In orexin neuron-ablated transgenic mice, the food-entrained rhythmicity of mPer2 expression in the brain and liver, the reversal of the sleep-wake cycle, and the recovery of daily food intake were unaltered compared with wild-type littermates. In contrast, orexin neuron-ablated mice had a severe deficit in displaying the normal food-anticipatory increases in wakefulness and locomotor activity under restricted feeding. Moreover, activity of orexin neurons markedly increased during the food-anticipatory period under restricted feeding in wild-type mice. Orexin neurons thus convey an efferent signal from putative food-entrainable oscillator or oscillators to increase wakefulness and locomotor activity.

Animals↗
PubMed2003

Serotonin and norepinephrine involvement in efferent pathways to the urethral rhabdosphincter: implications for treating stress urinary incontinence.

Stress urinary incontinence (SUI), the most common form of incontinence, continues to be a largely underdiagnosed problem that imposes large financial and quality-of-life burdens on many women but has few treatment options. Ongoing animal and early human studies have shown that monoamine neurotransmitters play key roles in controlling urethral storage and micturition reflexes. Motor neurons found in the Onuf nucleus of the sacral spinal cord control urethral function, and have several unique properties that distinguish them from other motor neurons. First, the neurons are uniformly smaller than other surrounding motor neurons and have bundled dendrites, allowing strong synchronous activation or inhibition. Second, the neurons demonstrate unique neurochemical profiles. Unlike neurons in surrounding areas, the motor neurons of the Onuf nucleus have dense populations of noradrenergic and serotonergic terminals. Animal studies have shown that alpha1-adrenoceptors and serotonin (5-hydroxytryptamine [5-HT]) receptors in the Onuf nucleus facilitate sphincter contraction. Agonists that stimulate these receptors facilitate the guarding or incontinence reflex, whereas antagonists that block the receptors inhibit this reflex. Therefore, boosting the effects of 5-HT and norepinephrine (NE) to enhance sphincter activity could be clinically promising for improving the symptoms of SUI. Importantly, the activity of the sphincter neurons can be increased pharmacologically during urine storage without interfering with bladder-sphincter synergy. Administering the 5-HT/NE uptake inhibitor duloxetine facilitates sphincter contraction during bladder filling but not during bladder contraction in micturition. This unique effect of duloxetine may be maintained by the selective neuromodulatory effects of 5-HT and NE on activation of sphincter motor neurons by the neurotransmitter glutamate. Prolonging the effect of naturally released NE and 5-HT with duloxetine could augment the body's normal processes for controlling urine storage and micturition. Early trials have demonstrated that duloxetine significantly reduces incontinence episodes and is well tolerated in the clinical setting.

Adrenergic Uptake Inhibitors↗
PubMed1989

Afferent and efferent pathways in T cell responses to MHC class I+, II-hepatocytes.

We have previously reported that purified hepatocytes stimulate significant in vitro allospecific cytotoxicity when cocultured with naive responder splenocytes in the mixed lymphocyte hepatocyte culture (MLHC). In this report we examined the expression of MHC antigens on the surface of hepatocytes, the phenotypic lymphocyte subset(s) that respond(s) to allogeneic hepatocytes, and the phenotype of allospecific cytolytic effectors generated in MLHC. Hepatocytes expressed MHC class I but not MHC class II antigens by immunofluorescent microscopy and fluorescence activated cell sorting. The lack of MHC class II on the surface of hepatocytes was also indirectly supported by the inability of hepatocytes to stimulate proliferation of a class II-directed allospecific helper T cell clone. The generation of allospecific cytotoxicity in MLHC required the participation of L3T4+, Ly2- T cells and L3T4-, Ly2+ T cells in the naive responder splenocyte population since depletion of these subsets with mAb and complement abrogated the development of allo-CTLs. Furthermore, adherent accessory cells in the naive responder splenocyte population appeared to play a role in the generation of allospecific cytotoxicity in MLHC since depletion of this population by plastic adherence and passage through a Sephadex G10 column resulted in significantly reduced allospecific cytotoxicity. Depletion of day 5 allosensitized cells of Ly2+ but not L3T4+ T cells by mAb and complement eliminated allospecific cytotoxicity--indicating that cytolytic effectors generated in MLHC appear to be L3T4-, Ly2+ T cells.

Animals↗