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 595 records · Page 33Linked to original sources
PubMed1985

Cardiorespiratory changes following chemical applications to gut serosa.

Application of 0.2-0.3 ml of 1 M ammonium chloride, 100 mM citric acid, 100 mM hydrochloric acid, 1% potassium chloride, 1% ammonium oxalate, 1% oxalic acid, 0.5% sodium hydroxide, 200 micrograms% bradykinin or 20 mg% capsaicin to gastrointestinal serosa produced a fall in blood pressure and inhibition of respiration in hypertensive as well as normotensive rats. In 6 (8%) of the animals studied, a fall in heart rate was also seen which was blocked by atropine. The blood pressure changes were independent of changes in heart rate. After acute abdominal vagotomy, while the respiratory inhibition following chemical application on gut serosa was enhanced, the cardiovascular responses were the same as before. In animals subjected to sympathetic denervation by spinal section at T5, celiac ganglionectomy or splanchnicotomy, a similar application produced an augmented respiratory response while the cardiovascular parameters were unaffected. These results show that the above inhibitions were mediated through the sympathetic afferents and a minor stimulation of respiration, via vagal afferents. The efferent pathway for the cardiac changes seems to be via vagus and the vascular changes via the sympathetics. In chronic vagotomized animals, the same stimulation produced a response similar to that seen in animals with intact vagus. An adaptive response may be operating in chronic animals reverting the status back to normal.

Ammonium Chloride↗
PubMed1989

Stimulation in prefrontal cortex area inhibits cardiovascular and motor components of the defence reaction in rats.

In the present investigation it was shown that electrical or chemical (D,L-homocysteic acid, DLH) stimulation in a defined area of the medial prefrontal cortex inhibits cardiovascular components of the defence reaction elicited by stimulation in the basal nucleus of the amygdala or in the hypothalamus in rats anaesthetized by Saffan. Electrical stimulation in the dorsal part of the nucleus accumbens or ventral part of the nucleus caudate had the same effect, while chemical stimulation (DLH) in these areas was not effective. In unanaesthetized rats stimulation in the prefrontal cortex or the nucleus accumbens inhibited cardiovascular and motor components of the defence reaction induced from the amygdala or hypothalamus. Stimulation in the described areas of the medial prefrontal cortex or nucleus accumbens does not induce general inhibition of motor activity since it did not affect operant, appetitive bar pressing. It is therefore concluded that the inhibition is selectively addressed to the motor activities associated with the defence reaction. It is suggested that inhibition of the cardiovascular components of the defence reaction must occur below hypothalamic level. The inhibition is most likely presynaptic since stimulation in the prefrontal cortex or nucleus accumbens alone did not produce any cardiovascular changes. It is unlikely that the efferent pathway originating in the prefrontal inhibitory area relays in the nucleus accumbens since microinjection of DLH into this nucleus was ineffective. Stimulation in "sympatho-inhibitory' areas (anterior hypothalamus, anterior cingulum) or in the nucleus raphe obscurus had no inhibitory effect on the cardiovascular components of the defence reaction.

Animals↗
PubMed1989

Cardiovascular and motor components of the defence reaction elicited in rats by electrical and chemical stimulation in amygdala.

In rats anesthetized with Saffan, electrical and chemical (D,L-homocysteic acid, DLH) stimulation in amygdala complex induced vasodilation in the hindlimb muscle, renal vasoconstriction and tachycardia. Chemical stimulation of cell bodies was effective only in the basolateral nucleus, while electrical stimulation produced the response from a larger area: central, basolateral and basomedial nuclei of amygdala. In non-anaesthetized rats, electrical stimulation in these nuclei elicited arching of the back, piloerection, sitting up and boxing with the forepaws or running, jumping or squealing. It is concluded that the area within the amygdala complex controlling the defence reaction is probably restricted to the basolateral nucleus, responses obtained from neighbouring nuclei might be due to activation of the afferent or efferent pathways leading to or from the basolateral nucleus.

Alfaxalone Alfadolone Mixture↗
PubMed1989

Ganglioglomerular nerves influence responsiveness of cat carotid body chemoreceptors to almitrine.

A bolus injection of almitrine bismesylate (0.5 mg.kg-1 i.v.) in anaesthetised artificially ventilated cats caused a significantly greater increase in carotid chemosensory discharge in animals with sectioned ipsilateral ganglioglomerular sympathetic nerves in comparison with a group in which these nerves were intact. Plasma levels of almitrine were similar in both groups. Responses to hypoxia and hypercapnia post-almitrine were also bigger if the ganglioglomerular nerves were cut. Domperidone (10-50 micrograms.kg-1 i.a), a dopamine D2 receptor antagonist, greatly increaed the responsiveness of chemoreceptors to almitrine in ganglioglomerular nerve-intact preparations. Almitrine-induced chemosensory activity was unaffected by illuminating the carotid bifurcation with light from a fibre optic lamp, regardless of whether or not the ganglioglomerular nerves were cut. It is concluded that almitrine may directly or indirectly activate an efferent pathway in the ganglioglomerular nerves to cause depression of chemoreceptor activity, possibly by releasing dopamine to act at D2 dopamine receptors in the carotid body.

Action Potentials↗
PubMed1996

The mammalian sympathetic prevertebral ganglia: integrative properties and role in the nervous control of digestive tract motility.

The prevertebral ganglia which are a constitutive part of the sympathetic system have long been considered as a simple relay on this efferent pathway. In fact, these ganglia must be considered as true peripheral nervous centres. They possess various integrative properties, such as projections of central and peripheral inputs onto the ganglionic neurones, gating of these projections and pacemaker activity of the ganglionic neurones. These properties explain the ability of these ganglia to participate in the regulation of various visceral functions, including digestive tract motility.

Animals↗
PubMed1985

Ontogenetic development of serotoninergic neurons in the brain of a teleost, the three-spined stickleback. An immunohistochemical analysis.

The ontogenetic development of serotoninergic neurons in the brain of the stickleback was investigated with the indirect immunocytochemical peroxidase-antiperoxidase technique, using a specific antibody to serotonin (5-hydroxytryptamine, 5-HT). Formation of neuronal populations takes place during embryonic development. By 80 h after fertilization, the first 5-HT perikarya have appeared in the ventricular zone of the hypothalamus (nucleus recessus lateralis) and the raphe region. At 108 h the first 5-HT perikarya can be observed in area praetectalis. At 118 h a transient group of 5-HT neurons appears rostral to the nucleus recessus lateralis, and at this same age the first 5-HT perikarya may be visualized in nucleus recessus posterioris. A group of 5-HT neurons appears in the dorsolateral tegmentum at 166 h (one day after hatching, which occurs at 120-144 h after fertilization). Differentiation of the neuronal populations, in terms of migration and formation of subdivisions, starts between 80 h and 94 h, and seems to be completed between 1 and 5 days after hatching. Raphe nuclei form an anterior group comprising nuclei raphe dorsalis, raphe medialis and a ventrolateral group, and a posterior group comprising a nucleus raphe pallidus/obscurus complex, a lateral nucleus reticularis paragigantocellularis and a ventromedial nucleus raphe magnus. The posterior and ventral raphe nuclei, which are well developed at the time of hatching, have not been visualized in the adult stickleback. While formation of 5-HT neuronal systems, as well as their primary efferent pathways, takes place during early ontogenetic development, the establishment of terminal areas and their subsequent differentiation apparently takes place during later ontogenetic stages. Most presumptive target areas are penetrated by 5-HT axons at hatching, although terminal formation does not seem to start until later. A considerable number of 5-HT neuronal groups present in the embryonic and newly hatched stickleback have not been visualized in the adult stickleback. This may be due to selective cell death, changes in transmitter phenotype or maturation of axonal transport processes during development.

Animals↗
PubMed1992

Dopamine receptor interactions: some implications for the treatment of Parkinson's disease.

Since the discovery that L-DOPA could alleviate the symptoms of Parkinson's disease, it has been assumed that the striatum is the site of action of the dopamine formed from L-DOPA. However, for the past 15 years, evidence has accumulated to suggest that dopamine is also released by the dendrites of dopamine neurons in the substantia nigra and D1 dopamine receptors in this region of the brain appear to play an important role in the actions of L-DOPA. Activation of D1 receptors in the substantia nigra may, in part, explain some of the synergistic effects of D1 and D2 agonists in animal models for Parkinson's disease. These effects are discussed in light of recent studies suggesting that dopamine, acting on D1 and D2 dopamine receptor subtypes, activates distinct efferent pathways from the striatum. Clinical studies suggest that these findings may have important implications for the treatment of Parkinson's disease.

Animals↗
PubMed1993

Direct projection from the nucleus of the optic tract to the medial vestibular nucleus in the cat.

The nucleus of the optic tract (NOT) serves as an important visuo-motor relay between the retina and preoculomotor structures that mediate optokinetic nystagmus. In the present study, the efferent targets of NOT were investigated using biocytin as an anterograde tracer. Following biocytin injections into NOT, labeled fibers were observed in each of the following efferent pathways: (1) those that project to the contralateral NOT via the posterior commissure; (2) those that course through the nucleus reticularis pontis oralis to terminate in the nucleus reticularis tegmenti pontis; and (3) those that descend via the medial lemniscus to the level of the medulla to terminate in the dorsolateral pontine nucleus, nucleus prepositus hypoglossi, medial vestibular nucleus and the inferior olive. Direct projections from the NOT to the medial vestibular nucleus may contribute to the residual optokinetic responses of the vestibular nucleus neurons following cerebellar or inferior olivary lesions.

Animals↗
PubMed1992

Analysis of intention tremor.

A marked effect of stereotaxic thalamotomy on intention tremor is described and a neurophysiological interpretation is offered. Tremor-generating activity seems to start in the ventral intermediate nucleus (VIM) of the thalamus, as revealed by recording of the unitary activity through a microelectrode at the tip of the insertion needle, after diminution of facilitatory input due to pathology of the cerebellum or its efferent pathway to the cerebrum. This secondary change within the VIM and the loss of facilitatory input leads to an intention tremor as one of the cerebellar symptoms seen in various neurological diseases.

Adult↗
PubMed1983

The hypothalamic paraventricular nucleus mediates the photoperiodic control of reproduction but not the effects of light on the circadian rhythm of activity.

Photoperiods of less than 12.5 h of light/24 h induce gonadal regression in the golden hamster. Photic information is relayed from the retina to the hypothalamic suprachiasmatic nucleus (SCN), a structure responsible for the generation of many circadian rhythms including the circadian rhythms in locomotor activity and pineal melatonin synthesis and release. Although pineal melatonin mediates the photoperiodic-neuroendocrine response, the complete neural circuit from the SCN to the pineal gland is unknown. Complete destruction of the hypothalamic paraventricular nucleus (PVN) prevented short-day-induced testicular regression without affecting the circadian rhythm of locomotor activity. The results indicate that the PVN plays an important role in the photoperiodic-neuroendocrine circuit and is responsible for relaying information from the SCN to the pineal. A different efferent pathway connects the SCN to structures in the brain responsible for locomotor activity.

Animals↗
PubMed1985

A direct projection from the nucleus oculomotorius to the retina in rats.

The centrifugal projection to the eye has been studied in rats with anterograde and retrograde tracing techniques. As a retrograde tracer Nuclear Yellow (NY) was used. Following NY injections into the vitreous body of the eye, labeled neurons were exclusively found bilaterally in nucleus oculomotorius. The course and termination site of the retinopetal fibers were studied with the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L). Iontophoretic injections of PHA-L in nucleus oculomotorius resulted in labeling of retinopetal fibers which reach the eye via the optic tract and optic nerve. Preterminal arborizations were found in the inner nuclear layer of the retina. In addition, labeled fibers have been observed which seem to terminate within the optic tract and optic nerve. It is suggested that the projection from the nucleus oculomotorius to the retina constitutes a link in the multisynaptic efferent pathway from the visual cortex to the eye, by which the visual cortex can influence the functioning of the retina.

Animals↗
PubMed1994

Anticonvulsant activity of the noradrenergic locus coeruleus system: role of beta mediation.

Many experimental observations have demonstrated the modulatory role exerted by several neural structures and neurotransmitters on spontaneous and paroxysmal bioelectric activity of the hippocampus. Recently, the control exerted by locus coeruleus (LC) and its noradrenergic (NA) efferent pathway on different experimental models of epilepsy (e.g. cortical cobalt chronic epilepsy, amygdaloid and hippocampal kindling) was emphasised. On this basis, a series of experiments was performed to elucidate the functional role of LC-NA system on the hippocampal penicillin (PCN) focus and the type of adrenergic receptor involved. The experiments were carried out on 25 rats in which an epileptiform hippocampal focus was obtained through intrahippocampal PCN administration (100-200 I.U.). In these conditions, LC, ipsilateral to PCN hippocampal focus, was stimulated before and after intraperitoneal (i.p.) administration of a beta-adrenergic receptor antagonist propranolol (2 mg/kg). Results showed a significant reduction of hippocampal spiking frequency during LC stimulation; after i.p. propranolol injection, LC stimulation, at the same parameters, failed to induce any sort of modification of PCN hippocampal spiking frequency. Furthermore, intrahippocampal application of a beta-selective agonist 2-fluoro-noradrenaline (2-FNA) mimics the inhibitory effects of LC stimulation. All data suggest that the LC-NA system is able to induce a net reduction of hippocampal epileptiform focus and the inhibitory NA control involves the activation of adrenergic beta receptors.

Animals↗
PubMed1994

Comparison of effects of bilateral injections of bicuculline and muscimol into the caudate-putamen of amygdaloid-kindled rats.

Bicuculline is an antagonist of gamma-aminobutyric acid (GABA) receptors, and muscimol is an agonist of GABA receptors. In this study, the effects of bilateral injections of bicuculline and muscimol into the caudate-putamen (CP) were compared in amygdaloid-kindled rats. Thirty minutes after the injection of bicuculline (1, 10 and 100 pmol per CP) or muscimol (10, 50 and 100 nmol per CP), the kindled amygdala was stimulated at the previously established generalized seizure triggering threshold (GST). Most doses of bicuculline caused no significant alteration either in the seizure stage or in the afterdischarge duration. Only the 100-pmol dose produced a marked reduction in the afterdischarge duration. With 10 nmol of muscimol, there was no significant change in the kindled seizure stage or in the afterdischarge duration. However, 50 and 100 nmol of muscimol markedly suppressed both parameters. These findings suggest that CP efferent pathways are involved in the mechanism that underlies the development of kindled amygdaloid seizures, and support the concept that GABA acts as an anticonvulsant in the brain.

Amygdala↗
PubMed1995

Stimulation of adenosine A2a receptors in the rat striatum induces catalepsy that is reversed by antagonists of N-methyl-D-aspartate receptors.

Bilateral infusion of the selective adenosine A2a agonist CGS 21680C (1 microgram per side) into the anterodorsal striatum of rats produced profound catalepsy. Intraperitoneal coadministration of the non-competitive N-methyl-D-aspartate (NMDA) antagonist dizocilpine (0.16 mg/kg) or the competitive NMDA antagonist CGP 37849 (4 mg/kg) completely reversed CGS 21680C-induced catalepsy, while lower doses of both NMDA antagonists induced no or only weak anticataleptic effects. The adenosine A2a receptor localization to striatopallidal neurons suggests that a selective activation of the striatopallidal efferent pathway is involved in the expression of catalepsy induced by intrastriatal infusion of CGS 21680C. In addition, striatopallidal neurons seem to be an important neuronal substrate of the anticataleptic effects of NMDA antagonists.

2-Amino-5-phosphonovalerate↗
PubMed1984

Spatio-temporal organization of a branched tecto-spinal/tecto-diencephalic neuronal system.

The aim of the present study was to identify in the rat the diencephalic nuclei addressed by ascending collaterals of tecto-spinal neurons. For this purpose we made use of anterograde axonal transport method to determine the pattern of diencephalic projections arising from the lateral portion of the superior colliculus where most of tecto-spinal neurons are lying. Next, we used the antidromic activation method to analyse whether some of these colliculo-diencephalic projections were provided through collaterals of tecto-spinal neurons. Following injections of wheatgerm agglutinin, conjugated with horseradish peroxidase, in the lateral part of the superior colliculus, anterograde labelling was observed in: the contralateral superior colliculus, the ipsilateral pretectal nuclei, subthalamic area (zona incerta and Forel field) and thalamic structures namely: dorsal and ventral lateral geniculate, parafascicular, posterior nuclear group, reuniens nuclei and lateral portion of medio-dorsal nucleus. Moreover, bilateral projections were revealed in the following thalamic nuclei: lateral posterior, ventro-medial, paracentral and central-lateral. In the electrophysiological study we established that the thalamic nuclei medio-dorsal/central-lateral, paracentral, ventral-medial and the zona incerta receive ascending collaterals of the tecto-spinal neurons. In addition, an axonal branch to the contralateral superior colliculus was also revealed. The various ascending and descending collaterals of each branched neuron exhibited a similar conduction time for action potentials. It is thus likely that the tecto-spinal/tecto-diencephalic neurons provide a synchronized influence on their targets. The functional implication of such a branched collicular efferent pathway is discussed. Considering that tecto-spinal neurons are one of the collicular neuronal populations on which the substantia nigra exerts its influence, new perspectives in the analysis of basal ganglia collicular relationships are given.

Animals↗
PubMed1985

Glutamate decarboxylase immunoreactivity in the intermediate grey layer of the superior colliculus in the cat.

Recent evidence suggests that gamma-aminobutyrate has a profound influence on the activity of premotor neurons in the intermediate grey layer of the superior colliculus. In the present study an antibody to glutamate decarboxylase, the synthesizing enzyme for gamma-aminobutyrate, was used to identify and characterize the structures in the intermediate grey layer of the cat that use gamma-aminobutyrate as a transmitter. The material was examined with both the light and electron microscope. Glutamate decarboxylase immunoreactivity was confined, for the most part, to axon terminals. Glutamate decarboxylase positive terminals almost completely cover the soma and proximal dendrites of the large neurons that are characteristic of this layer. Other glutamate decarboxylase positive terminals contact smaller, presumably more distal dendrites. By combining the glutamate decarboxylase immunocytochemistry with the retrograde transport of horseradish peroxidase in single animals, it was demonstrated that the cells of origin of the major descending efferent pathway from the intermediate grey layer, the predorsal bundle, are heavily contacted by glutamate decarboxylase immunoreactive terminals.

Animals↗
PubMed1991

Collateralization of periaqueductal gray neurons to forebrain or diencephalon and to the medullary nucleus raphe magnus in the rat.

Antinociceptive effects elicited from the midbrain may involve both ascending and descending projections from the periaqueductal gray and dorsal raphe nucleus. To investigate the relationship between these different efferent pathways in the rat, we performed a double-labeling study using two retrograde tracers, colloidal gold-coupled wheatgerm agglutinin-apo horseradish peroxidase and a fluorescent dye. One tracer was microinjected in the medullary nucleus raphe magnus; the second was injected into one of several regions rostral to the periaqueductal gray that have been implicated in nociceptive and antinociceptive processes. The results can be grouped into two categories. First, injections into the ventrobasal thalamus, lateral hypothalamus, amygdala, and cerebral cortex labeled neurons in the dorsal raphe nucleus but not in the periaqueductal gray. Up to 90% of these projection neurons were serotonin immunoreactive, and up to 17% were also retrogradely labeled from the nucleus raphe magnus. Second, only injections into the ventrobasal hypothalamus (which included the beta-endorphin-containing arcuate neurons) or into the medial thalamus labeled neurons in the periaqueductal gray itself. Injections into the medial thalamus, but not into the ventrobasal hypothalamus, also labeled neurons in the dorsal raphe nucleus. Up to 20% of the neurons retrogradely labeled from these regions were also retrogradely labeled from nucleus raphe magnus. The presence of large populations of rostrally projecting periaqueductal gray neurons that collateralize to the nucleus raphe magnus implies that activity in ascending projections necessarily accompanies any activation of the periaqueductal gray-nucleus raphe magnus pathway. Possibly, projections from the medial thalamus and medial hypothalamus mediate antinociceptive effects that complement descending inhibition. Finally, possible antidromic activation of these pathways must be considered when interpreting the results of electrical brain stimulation studies.

Animals↗
PubMed1996

Increased nerve growth factor inducible-A gene and c-fos messenger RNA levels in the rat midbrain and hindbrain associated with the cardiovascular response to electrical stimulation of the mesencephalic cuneiform nucleus.

Functional neuronal connections associated with the cardiovascular response to unilateral low-intensity electrical stimulation of the mesencephalic cuneiform nucleus were examined in the halothane-anaesthetized and paralysed rat by in situ hybridization histochemistry using specific 35S-labelled oligonucleotides for detection of nerve growth factor inducible-A gene (NGFI-A) and c-fos messenger RNAs. Stimulation of the cuneiform nucleus increased mean arterial pressure and heart rate by 20 +/- 0.5 mmHg and 35 +/- 3 b.p.m., respectively, while no significant cardiovascular response was observed in animals stimulated in the inferior colliculus or in sham-operated animals. Cuneiform nucleus stimulation produced increased NGFI-A and c-fos messenger RNA levels in the Kölliker-Fuse and parabrachial nuclei ipsilaterally, and the cuneiform nucleus, dorsal periaqueductal gray and caudal ventrolateral medulla bilaterally at levels significantly greater than those in inferior colliculus-stimulated, sham-operated and naive, unoperated animals. NGFI-A, but not c-fos, messenger RNA expression was increased bilaterally in the caudal portion of the nucleus of the solitary tract and inferior olive. These results are consistent with previous neuroanatomical tract-tracing studies of afferent and efferent pathways from the cuneiform nucleus and indicate that these midbrain and hindbrain structures may be involved in the pressor and tachycardic responses associated with stimulation of the cuneiform nucleus. The ipsilateral nature of responses in certain brain areas may be explained by the absence of decussating pathways and/or the presence of multisynaptic connections which attenuate bilateral signal transmission. Characterization of these activated neuronal structures using other compatible labelling techniques should further elucidate the mechanisms by which these central nervous system structures are integrated in the cardiovascular responses to stimulation of the cuneiform nucleus.

Animals↗