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 415 records · Page 23Linked to original sources
PubMed1975

Cat parastriate cortex: a primary or secondary visual area.

The purpose of this study was to determine to what extent the cat parastriate cortex processes afferent geniculate activity in a way similar to that in area 17. The area explored was located on the lateral gyrus between the Horsley-Clarke coordinates A1 to 4 and L3 to 4. The receptive-field properties of area 18 cells and their responses to electrical stimulation of afferent and efferent pathways were measured with the same methods as described previously in area 17. Mutual correlations among these items were calculated and compared with the respective data from area 17. The results of this correlative analysis revealed numerous similarities between the two areas with regard to their afferent and efferent connections and their intrinsic organization. Consequently, the structure of the receptive fields and their numerical distribution resembled those in area 17. The same was true for the correlations between receptive-field parameters and afferent and efferent connectivity. The main differences were that area 18 cells had larger receptive fields and responded to considerably higher stimulus velocities. It is suggest-d that these differences are caused by the fact that area 18 receives subcortical afferents of the Y-type, whereas the dominant input to area 17 comes from the X-system. It is concluded that the area investigated in this study is organized in parallel to area 17 and deals with other aspects of visual information than area 17.

Animals↗
PubMed2003

Neural control of the urethra and development of pharmacotherapy for stress urinary incontinence.

This review discusses the control of the urethra by the central nervous system, emphasizing the importance of nervous system control and the role of serotonin and noradrenaline in storage, micturition and sphincter reflexes. The concept of pharmacological neuromodulation and the use of pharmacological therapy as first-line therapy for stress urinary incontinence (SUI) is presented. Coordination between the urinary bladder and urethra is mediated by many reflex pathways organized in the brain and spinal cord. During bladder filling, activation of mechanoreceptor afferent nerves in the bladder wall triggers firing in the cholinergic efferent pathways to the external urethral sphincter and in sympathetic adrenergic pathways to the urethral smooth muscle. These storage reflexes depend on interneuronal circuitry in the spinal cord and are modulated by descending pathways. It would therefore seem that neurotransmission in the central nervous system and periphery may be important in SUI, and moreover that pharmacological agents affecting these neurotransmitter pathways may be used to treat SUI. The central and peripheral mechanisms of action of duloxetine affect serotonin and noradrenaline neurotransmission in ways that may ameliorate the symptoms of SUI.

Adrenergic Uptake Inhibitors↗
PubMed1996

The use of conditioning to probe for CNS pathways that regulate fever and NK cell activity.

Immune and central nervous system (CNS) interactions are complicated because afferent signals from the immune system to the CNS in response to antigens or infections may elicit an immediate efferent response to the immune system. This communication loop is required for the homeostatic regulation of the immune system. Conditioning can be used as a tool to take the communication loop apart. In conditioned animals, the conditioned stimulus can be employed later to trigger the site of the association memory located within CNS, and set off the efferent pathway. Conditioning therefore allows one to isolate and identify the potential circuits in the brain that becomes conditioned. We have conditioned a pathway in the brain which can be used to modulate core body temperature (Tc) and natural killer (NK) cell activity. The Tc and NK cell activity are used as readouts to detect the expression of the conditioned response which is taking place in the brain. Since various cytokines (IFN, IL-1 etc) that are produced by antigenic stimulation invariably raise fever, it appears that the immune system could signal the CNS with nonspecific cytokines that activate the hypothalamic-pituitary pathway to modulate core body temperature. These observations infer that the thermoregulatory pathway in the brain becomes conditioned and points to a common pathway of communication in which interferon-beta, prostaglandin E2, CRH and ACTH appear to play a role in modulating both Tc and NK cell activity.

Animals↗
PubMed1989

Collateral projections of predorsal bundle cells of the superior colliculus in the rat.

The deep layers of the superior colliculus contain cells which are premotor in the sense that they respond prior to the onset of shifts in gaze and send axons, by way of a pathway called the predorsal bundle, to the contralateral brainstem gaze centers and cervical spinal cord. Previous studies have suggested that these cells also contribute to other efferent pathways which arise in the deep layers. The present study examines the contributions of the cells of origin of the predorsal bundle to these additional pathways as a step toward understanding their roles in gaze mechanisms. In one series of experiments, retrograde tracers were used to compare the laminar distribution of predorsal bundle cells with the distributions of the cells of origin of three other pathways: those that project to the intralaminar region of the dorsal thalamus, those that project to the contralateral superior colliculus, and those that project to the ipsilateral brainstem tegmentum. Predorsal bundle cells were found primarily in stratum griseum intermedium sublayer b. This distribution overlaps extensively with the distribution of colliculus cells that project to the intralaminar region of the thalamus. In contrast, the majority of the colliculus cells that project to either the contralateral superior colliculus or the ipsilateral brainstem tegmentum do not overlap extensively with the predorsal bundle cells; instead, they are primarily located dorsal or ventral to sublayer b of stratum griseum intermedium. In a second series of experiments, two regions were injected with different retrograde fluorescent traces in single animals in order to study the collateral projections of the cells of origin of these pathways. The results indicate that many predorsal bundle cells project to the intralaminar region of the dorsal thalamus but that only a few contribute to the tectotectal pathway. The results also indicate that few tectotectal cells contribute to the ipsilateral tectobulbar pathway.

Animals↗
PubMed1981

Retinal projection in a non-visual area after bilateral tectal ablation in goldfish.

If, in the adult goldfish, one optic tectum is ablated, the regenerating optic axons from the contralateral retina innervate the remaining tectum, where they form a retinotopically ordered map. The pathway for this induced ipsilateral projection coincides with many of the pathways which normally connect the two tecta, but early in regeneration the optic fibres also enter non-visual centres to which there are degenerating tectal efferent pathways to follow. We have therefore now investigated the fate of regenerating optic axons in goldfish from which both optic tecta have been removed; they are found to innervate non-visual centres, where again they generate a retinotopic map.

Animals↗
PubMed1993

Somatostatin inhibits pancreatic enzyme secretion at a central vagal site.

The mechanisms and site of action of somatostatin-induced inhibition of pancreatic enzyme secretion were investigated using different stimulants of pancreatic secretion acting on different sites in anesthetized rats. Administration of graded doses of somatostatin-14 resulted in a dose-related inhibition of pancreatic protein secretion evoked by 2-deoxy-D-glucose, a central vagal stimulant that acts by stimulating the dorsal vagal nuclei. The lowest effective dose of somatostatin-14 was 1.0 microgram.kg-1 x h-1; maximal effective dose was 25 micrograms.kg-1 x h-1, which resulted in complete inhibition of protein output. Similarly, somatostatin-14 at a dose of 25 micrograms.kg-1 x h-1 also completely inhibited pancreatic protein secretion in response to a physiological concentration of cholecystokinin octapeptide (CCK-8), which acts via a vagal afferent pathway. In contrast, pancreatic protein outputs evoked by bethanechol, which directly stimulates pancreatic muscarinic receptors, or electrical stimulation of the vagal trunk, which activates the vagal efferent pathway, were unaffected by somatostatin-14. In separate studies, we demonstrated that perivagal treatment with the sensory neurotoxin capsaicin impaired pancreatic responses to CCK-8 but had no effect on the inhibitory action of somatostatin-14 on pancreatic secretion evoked by 2-deoxy-D-glucose, ruling out an effect of somatostatin on the vagal afferent pathway. Similarly we also demonstrated that perineural capsaicin treatment of the celiac-superior mesenteric ganglia did not affect the inhibitory action of somatostatin. These findings indicate that somatostatin inhibits 2-deoxy-D-glucose- and CCK-8-evoked pancreatic enzyme secretion via a vagal pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Changes in muscle afferents, motoneurons and motor drive during muscle fatigue.

Fatigue is a reduction of maximal muscle force or power that occurs with exercise. It is accompanied by changes at multiple levels in the motor pathway and also by changes in the discharge patterns of muscle afferents. Changes in afferent firing can lead to altered perceptions and can also act on the efferent pathway. Changes in the motor pathway include slowing of motor unit firing rates during sustained maximal voluntary contractions (MVCs). Muscle responses to stimulation at different levels of the motor pathway also change. Transcranial magnetic stimulation of the motor cortex and stimulation of descending tracts in the spinal cord in human subjects show an increase in the response of the cortex and a decrease in response of the motoneuron pool during sustained MVCs. In addition, the silent period following magnetic stimulation is prolonged. During relaxation after fatiguing exercise, muscle responses to stimulation of the motor cortex are initially facilitated and are then depressed for many minutes, whereas responses to descending tract stimulation are initially depressed but recover over about 2 min. Although some of the loss of force of fatigue does occur through inadequate drive to the muscle, it is not clear which, if any, of the changes described in the cortex or the motoneurons are responsible for loss of maximal voluntary force and thus contribute to fatigue. Changes may be associated with muscle fatigue without causing it.

Animals↗
PubMed1990

[The role of diuretics in the treatment of chronic heart failure].

Altered renal function with renal NaCl-retention can be observed early in the course of congestive heart failure. The afferent pathway of this altered regulation involves changes occurring in the high pressure system as a consequence of foreward failure such as an increase in baroreceptor reflex activity. Efferent pathways may include the renin-angiotensin-aldosterone system, the sympathetic nervous system, prostaglandins, dopamine, ANF, and AVP. At present, the relative importance of these systems in mediating renal NaCl-retention in heart failure is still unclear. Expansion of the extracellular fluid volume as a consequence of renal NaCl-retention may, at least acutely, compensate for compromised myocardial function via the Frank-Starling mechanism. As a consequence of volume expansion, chronically increased cardiac preload and possibly afterload may however even aggravate cardiac failure. Diuretics may therefore induce variable effects in patients with congestive heart failure. Acutely, they may ameliorate symptoms of congestion in spite of the possibility of a further decrease in cardiac index. Chronically, they may reduce cardiac pre- and afterload. Through a variety of mechanisms, they may therefore increase cardiac performance in spite of a fall in filling pressures.

Diuretics↗
PubMed2002

Baroreceptor reflex pathways and neurotransmitters: 10 years on.

The central nervous system plays a critical role in the management of blood flow to the tissues and its return to the heart and lungs. This is achieved by a complex interplay of neural efferent pathways, humoral mechanisms and afferent pathways. In this review, we focus on recent progress (within the past 10 years) that has been made in the sympathetic control of arterial blood pressure with a special emphasis on the role of baroreceptor mechanisms and central neurotransmitters. In particular, we focus on new features since 1991, such as neurotransmission in the nucleus tractus solitarius, the role of neurons in the most caudal part of the ventrolateral medulla oblongata and the increasing understanding of the exquisite control of different sympathetic pathways by different neurotransmitter systems.

Animals↗
PubMed1991

Maturation of lower extremity EMG responses to postural perturbations: relationship of response-latencies to development of fastest central and peripheral efferents.

EMG responses to toe-up tilt perturbations on a movable platform system were analysed in 86 children between the age of 12 months and 13 years. To assess the relative contribution of peripheral and central nerve conduction properties, a concomitant recording of the fastest efferent pathways in the central and peripheral motor system was made using non-invasive transcranial magnetic stimulation of motor cortex and peripheral nerve roots. This allowed the determination of the fastest downstream efferent connection times from motor cortex to lumbar motor neuron pools and to measure the fastest efferent conduction from these motor neuron pools to effector muscles in the lower leg. The sequence observed for stance stabilizing EMG responses was similar to that obtained in earlier studies with short latency (SL) and middle latency (ML) companents occurring in the stretched triceps surae muscle and long latency (LL) responses occurring in the non-stretched tibialis anterior muscle. Homologous responses were also obtained in upper leg muscles, being recruited consistently later than those in lower leg muscles across all age groups. In the short latency range two different SL1- and SL2-responses were obtained in children of all age groups as well as in adult controls. Both the SL1- and the SL2-responses showed a flat developmental profile, reaching adult values between 20 and 30 months of age which correlated with that of the fastest efferents from lumbar motor neuron pools to leg muscles, i.e. the final motor path. ML-responses showed a steeper developmental profile.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Light enhances sympathetic and suppresses vagal outflows and lesions including the suprachiasmatic nucleus eliminate these changes in rats.

Neurons in the suprachiasmatic nucleus (SCN) are suggested to be involved in the mechanism of glucose homeostasis. This mechanism was examined by studies on the effect of illumination on the activity of autonomic efferents to the adrenals, pancreas and liver. Exposure of one eye of anesthetized rats to light enhanced the efferent activity of the adrenal nerve and suppressed that of vagal pancreatic and hepatic nerves. No change in efferent activities of these nerves was observed on light-stimulation of rats with lesions that included the bilateral SCN. These findings indicate that light signals modulate visceral functions including metabolic processes through the retinohypothalamic tract probably via the SCN to autonomic efferent pathways innervating visceral organs.

Adrenal Glands↗
PubMed2001

Motor control of airway goblet cells and glands.

Activation of nerves increases airway mucus secretion. The mucus derives from submucosal glands and epithelial goblet cells. Depending upon species and airway level, innervation comprises parasympathetic (cholinergic), sympathetic (adrenergic) and 'sensory-efferent' pathways. In all species studied, cholinergic mechanisms predominate, particularly in human airways. Muscarinic M3 receptors on the secretory cells mediate the cholinergic response. Tachykinins (substance P and neurokinin A) mediate the sensory-efferent response, acting via tachykinin NK1 receptors. Endogenous mechanisms regulate the magnitude of neurogenic secretion, including enzymes (degrade neurotransmitters), nitric oxide (NO) and vasoactive intestinal peptide (VIP) (regulate stimulated secretion), and muscarinic M2 autoreceptors (inhibit acetylcholine release). Exogenous opioids also inhibit neurogenic secretion prejunctionally. Both VIP and opioids act by opening large conductance, calcium-activated potassium (BK(Ca)) channels. Present understanding of neural control of mucus secretion in animal airways requires translation into human data. This information should lead to rational development of drugs for bronchial diseases in which neurogenic mucus hypersecretion contributes to pathophysiology, including chronic bronchitis and asthma.

Animals↗
PubMed1975

Cardiac acceleration in man elicited by a muscle-heart reflex.

The shortening of the R-R interval in response to voluntary and electrically induced isometric muscle contractions of short duration was investigated in 15 volunteers. In some of those experiments the effect of vagal blockade was also studied. The results show: 1) a lag time between the start of the contraction and the following decrease in R-R interval duration of 550 milliseconds; 2) a similar R-R interval response due to voluntary and electrically induced contractions of the same force; 3) no shortening of the R-R interval when the skin is stimulated without ensuing muscular contraction; 4) a complete disappearance of the response to isometric contractions during vagal blockade. A difference in lag time between the onset of arm contraction and cardiac acceleration could not be demonstrated. Most of the results give strong evidence to the existence of a muscle-heart reflex in man, involved in the instantaneous cardiac acceleration at the onset of exercise, that has its origin in the muscles and the vagal nerves as its efferent pathway.

Adolescent↗
PubMed1998

Contralateral Acoustic Effect of Transient Evoked Otoacoustic Emissions in Neonates.

Contralateral acoustic stimulation (CAS) has the effect of reducing the amplitude of transient evoked otoacoustic emissions (TEOAE) of the opposite cochlea. This phenomenon is considered to be mediated via the efferent pathway, from the superior olivary complex through the medial olivocochlear system to the contralateral cochlea. The assessment of this suppressive effect provides an objective and noninvasive technique for exploring the function of the efferent auditory system in humans. Two previous studies investigated the suppression effect of TEOAE in newborns and revealed a significant effect in 18 full-term neonates. In this study, the effect of contralateral acoustic stimulation on TEOAE was investigated in 13 full-term neonates (gestational age, 40-42 weeks). The TEOAE were recorded alternately with and without simultaneous, contralateral white noise. The CAS effect of TEOAE was present in all subjects; a mean of 2.21 dB +/- 1.7 (21% +/- 9.3%) was found. Our study demonstrated additional support for the functional maturity of the medial olivocochlear efferent system from birth.

Journal Article↗
PubMed1988

Immunohistochemical localization of monoamines and cyclic nucleotides. Their application in quantitative immunofluorescence studies and tracing monoaminergic neuronal connections.

We have described immunocytochemical methods for the direct visualization of monoamine- and cGMP-containing neurons, using antibodies to the primary or secondary messengers themselves. The specificity and affinity of these antibodies were determined using quantitative immunofluorescence of gelatin models, as non-biological models, to which the native substances and their possibly cross-reacting compounds were incorporated. The use of retro- and anterograde tracers both in conjunction with immunohistochemical procedures provides the possibility to characterize transmitter specifically afferent and efferent pathways. With the presented double-label immunocytochemical procedures it is feasible to visualize and trace a projection between two brain areas, and in addition to specify the transmitters which are involved in their afferents and efferents and their target neurons and neurons of origin. Using the SCG, as a biological model, we could demonstrate that cGMP levels in individual cells could be elevated by cholinergic agonists. Moreover, using quantitative immunofluorescence of cGMP as a post- or presynaptic marker we have the possibility to measure the post-/presynaptic effects of monoamines or neuropeptides in individual neurons.

Animals↗
PubMed2001

Neural control of the urethra.

Coordination between the urinary bladder and the urethra is mediated by multiple reflex pathways organized in the brain and spinal cord. Some reflexes promote urine storage; whereas other reflexes facilitate voiding. During bladder filling, activation of mechanoreceptor afferent nerves in the bladder wall triggers firing in the cholinergic efferent pathways to the external urethral sphincter (EUS) and in sympathetic adrenergic pathways to the urethral smooth muscle. These storage reflexes are dependent upon interneuronal circuitry in the spinal cord. During voiding the spinal storage reflexes are inhibited by supraspinal mechanisms which originate in the pontine micturition center. Glutamatergic, serotonergic and alpha, adrenergic excitatory transmission as well as GABAergic/glycinergic inhibitory transmission have been implicated in the central control of sphincter reflexes. During voiding, a parasympathetic nitrergic inhibitory input to the urethral smooth is activated. This reflex mechanism which is triggered by bladder afferents persists in paraplegic rats and therefore must be mediated at least in part by spinal interneuronal circuitry. In female rats, the parasympathetic nitrergic pathway is prominent; but in male rats it is obscured by a dominant parasympathetic cholinergic excitatory input to the urethral smooth muscle. The function of the cholinergic pathway in voiding is uncertain. Stimulation of urethral afferents can also influence bladder activity. Contraction of the external urethral sphincter activates afferents that inhibit reflex bladder contractions; whereas infusion of fluid through the urethra facilitates bladder contractions. These reflexes are also organized in the spinal cord and presumably play a role in urine storage and elimination. Alterations in primitive bladder-to-urethra and urethra-to-bladder reflex mechanisms may contribute to neurogenic bladder dysfunction.

Afferent Pathways↗
PubMed2005

Central nervous control of micturition and urine storage.

The micturition reflex is one of the autonomic reflexes, but the release of urine is regulated by voluntary neural mechanisms that involve centers in the brain and spinal cord. The micturition reflex is a bladder-to-bladder contraction reflex for which the reflex center is located in the rostral pontine tegmentum (pontine micturition center: PMC). There are two afferent pathways from the bladder to the brain. One is the dorsal system and the other is the spinothalamic tract. Afferents to the PMC ascend in the spinotegmental tract, which run through the lateral funiculus of the spinal cord. The efferent pathway from the PMC also runs through the lateral funiculus of the spinal cord to inhibit the thoracolumbar sympathetic nucleus and the sacral pudendal nerve nucleus, while promoting the activity of the sacral parasymapathetic nucleus. Inhibition of the sympathetic nucleus and pudendal nerve nucleus induces relaxation of the bladder neck and the external urethral sphincter, respectively. There are two centers that inhibit micturition in the pons, which are the pontine urine storage center and the rostral pontine reticular formation. In the lumbosacral cord, excitatory glutamatergic and inhibitory glycinergic/GABAergic neurons influence both the afferent and efferent limbs of the micturition reflex. The activity of these neurons is affected by the pontine activity. There are various excitatory and inhibitory areas co-existing in the brain, but the brain has an overall inhibitory effect on micturition, and thus maintains continence. For micturition to occur, the cerebrum must abate its inhibitory influence on the PMC.

Animals↗
PubMed1981

Neurotensin: first report of a cortical pathway.

Neurotensin is one of a growing number of putative peptidergic neurotransmitters common to both gut and brain. It has been localised in many areas of the central nervous system including the amygdala, hypothalamus and brain stem, although its physiological significance is unknown. Using a specific antiserum to neurotensin and immunocytochemical techniques, we have investigated the distribution of neurotensin and neurotensin containing pathways in the rat limbic system. Immunoreactive neurotensin was found in all areas of the limbic system and within the limbic cortex. In addition a previously unreported group of neurotensin-containing cell bodies was found in the subicular region of the hippocampus.. In serial sections we were able to trace a pathway which appears to be the first peptide-containing pathway to be reported in the cerebral cortex from the dorsal hippocampus to the anterior cingulate cortex, following the path of the cingulate bundle. The presence of neurotensin (a putative excitatory transmitter) in this new hippocampal efferent pathway indicates that it may have an important role in cortical "association" mechanisms and limbic cortex functions.

Animals↗