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PubMed1984

The laminar organization of the lateral geniculate body and the striate cortex in the tree shrew (Tupaia glis).

The organization of geniculostriate projections in Tupaia was studied using three separate methods, anterograde transport from the lateral geniculate, retrograde transport from the striate cortex, and reconstruction of single geniculostriate axons. The results show that each layer of the lateral geniculate body has a unique pattern of projections to the striate cortex, and each pattern consists of a major and a minor target. The two ipsilateral layers project to thin subtiers of layer IV: the major target of geniculate layer 1 is the top of IVa; the major target of geniculate layer 5 is the base of IVb. The minor target of layer 1 is the major target of layer 5. Two of the contralateral layers can be matched to the ipsilateral layers. Layers 1 and 2 are a matched pair and project to IVa; layers 4 and 5 are a matched pair and project to IVb. Thus, projections of a matched pair overlap. The remaining two contralateral layers, 3 and 6, project chiefly to cortical layer III. Layer 3 projects to layers IIIb and I and seems to be the counterpart of the parvocellular C layers in the cat and the intercalated layers in primates. Layer 6 projects to the base of IIIc in a zone contiguous with IVa. This contiguity raises the issue of whether the base of IIIc might actually be a part of layer IV. If this were the case, the two tiers of layer IV which are separated by a conspicuous cleft might be considered two subdivisions of layer IVb.

Afferent Pathways↗
PubMed1981

Neural pathways involved in the hypothalamic integration of autonomic responses.

Recent mapping studies of hypothalamic and autonomic mechanisms have considerably extended our understanding of the anatomy of this system. The pattern of connections emerging from physiological, anatomical, and histochemical experiments suggests several conclusions about the functional organization of the system as well. Recent evidence supports the idea that the hypothalamic (and other limbic) areas involved in the control of ingestion and metabolism form the rostral pole of a longitudinally and hierarchically organized system that elaborates autonomic responses that influence the energy economy of the animal. Substantially the same pathways are apparently responsible for the modulation of ingestive behavior as well. This circuitry, the "visceromotor system" in Nauta's terminology, seems to weld afferent inputs, particularly those of the gustatory and visceral receptors, into a coordinated integrative control strategy influencing autonomic responses. In addition, the system seems to have unique tissue properties, at least at its two periventricularly located sites of integration with special access to both humorally and ventricularly circulated substrates. These nodes, the basomedial hypothalamus and the vagal complex of the medulla, seem to share similar biochemical specializations reflected in susceptibility to goldthioglucose toxicity, specific insulin binding, and susceptibility to alloxan diabetes.

Afferent Pathways↗
PubMedDate not supplied

[The morphological characteristics of the parasympathetic innervation of the pyloric sphincter in the cat].

The method of axonal transport of horse-radish peroxidase was used to detect the localization of neurons in the dorsal motor nucleus of the vagus nerve sending the axons to the pyloric sphincter. The investigation was carried out in cats. Under study were also morphological features of the nodular ganglion responsible for afferent innervation of the sphincter. The maximum amount of the corresponding cells are found in the dorsomedial part of the dorsal motor nucleus in the area from +1.0 to +2.0 mm (with respect to obex). The afferent neurons to which information comes from interoceptors of the sphincter zone along the vagus nerve fibers, are distributed in the left and right nodular ganglia almost evenly. The major part of these cells have the area of 300-800 mkm2.

Afferent Pathways↗
PubMed1994

Unexplained syncope: diagnostic value of tilt-table testing.

Vasovagal syncope is a common syncope in patients who have no structural heart disease and occurs more often in young adults. It typically occurs in the erect posture, either standing or sitting. Upon recognition of the prodrome associated with NCS, subjects may avert syncope by lying down or putting the head between the knees. Use of head-up tilting is a recognized diagnostic tool and widely used for the evaluation of vasovagal syncope. However, cardiac diagnostic tests are not 100% accurate. This fact was recently underscored by what occurred in the recent tragic loss, due to ventricular fibrillation, of basketball star Reggie Lewis of the Boston Celtics. It is alleged that the tilt-table test was positive but that he also had structural heart disease. The most important diagnostic tool is the physician's clinical judgment.

Adult↗
PubMed1993

[Exploration of the efferent system in man: basic and clinical results].

Since 1989, the exploration of the medial efferent system has been possible in human by using a non-invasive technique consisting in the association of the contralateral acoustic stimulation and the evoked otoacoustic emissions (EOAEs). This exploration presents a great interest for fundamental auditory research because it is the sole means of exploring in human these cochlear efferent neurons synapsing at the base of the outer hair cells. The function of this system is still unknown. The interest of such an exploration in clinical research is now becoming obvious such that it would be not only useful but also necessary to establish a precise diagnosis in particular pathologies. The aim of the present paper is to expose basic results obtained on the medial efferent system in normal subjects and above all to present findings for pathological ears, among which figure in particular: retrocochlear pathologies, hyperacousia, noise-induced hearing loss, tinnitus. In addition to the diagnostic interest of the exploration of the medial efferent system, a knowledge of its functioning will probably allow its role in audition to be determined.

Acoustic Stimulation↗
PubMed1993

Impulse patterns of single encoding sites of human secondary muscle spindle afferents.

1. By recording single-fibre action potentials (APs) from human sacral nerve roots, the impulse patterns of 6 secondary spindle afferents could be identified, analysed and compared with the impulse trains of oscillatory firing alpha 2-motoneurons. 2. Secondary spindle afferents fired with single APs, doublets, bursts and equidistant APs. On the assumption that the most simple firing pattern of a single fibre with a shortest interspike interval (II) of 80 msec was generated by a single encoding site, the firing patterns of the other afferents could be splitted into firing patterns of single encoding sites with similar II distributions and also with a shortest II of about 80 msec. 3. Successive IIs also reflected the different ways of firing of the secondary muscle spindle afferents. A fibre from a paraplegic with bladder dyssynergia seemed to show a higher activity than a comparable probably normal fibre. The doublet IIs of two secondary spindle afferents ranged from about 9 to 14 msec with peaks at 10.2, 11.2 and 13 msec in the distributions. Multiple encoder sites increased discharge rates of parent fibres, but did not always regularize the output discharge. 4. The simultaneously plotted impulse patterns of 4 secondary spindle afferents showed coordinated firing: they did not fire simultaneously but regularized the summed activity. A phase of 50 msec (range 30 to 70 msec) often occurred between the spindle afferent APs and the impulse trains of an oscillatory firing alpha 2-motoneuron. An afferent drive of the oscillator with a certain phase is likely.

Action Potentials↗
PubMed2005

Parasympathetic mediated pupillary dilation elicited by lingual nerve stimulation in cats.

PURPOSE: To determine the autonomic efferent nerve pathways for the reflex pupillary dilation elicited by somatic stimulation in cats. METHODS: Cats anesthetized with a mixture of alpha-chloralose (50 mg/kg) and urethane (100 mg/kg) were intubated and paralyzed by intravenous injection of pancuronium bromide. The central cut end of the lingual nerve (LN) was stimulated electrically to simulate somatic stimulation, and 1 microL of lidocaine (2%) was microinjected into the Vsp or the EW nucleus to determine its effect on the pupillary dilation induced by LN stimulation. The effect of electrically stimulating the Vsp or sectioning the superior cervical sympathetic nerve (CSN) on the pupillary response was also examined. RESULTS: Stimulation of the LN or the trigeminal spinal nucleus (Vsp) evoked pupillary dilation in a frequency- and intensity-dependent manner. These responses were not affected by sectioning the ipsilateral or both CSNs. The pupillary responses were markedly suppressed by microinjecting lidocaine into the ipsilateral Vsp or the Edinger-Westphal (EW) nucleus, but not by injection into the contralateral Vsp. CONCLUSIONS: These results indicate that the Vsp and EW nucleus act as bulbar relay centers for pupillary dilation elicited by LN stimulation and suggest that the efferent arc of the response is a parasympathetic pathway. The contralateral pupillary dilation appears to be mediated, at least in part, by fibers projecting from the Vsp to the contralateral EW nucleus.

Animals↗
PubMed1996

Glycinergic inhibition in the turtle spinal cord regulates the intensity and pattern of fictive flexion reflex motor output.

Application of strychnine sulfate (10-50 mu M) to the anterior hindlimb enlargement of the turtle spinal cord increased the amplitude of the ipsilateral fictive flexion reflex and revealed a contralateral (crossed) fictive flexion reflex response to cutaneous stimulation of the foot. Strychnine abolished the crossed inhibition of fictive flexion reflex that was normally evoked by contralateral foot stimulation, unmasking the crossed excitation. Our observations are consistent with the hypothesis that intraspinal inhibition mediated by strychnine-sensitive glycine receptors regulates the amplitude of fictive flexion reflex motor output and confines the response to the appropriate neural pathways.

Animals↗
PubMed1979

The spinal origin of the sympathetic nerve fibres to the vascular and secretory components of the rat submaxillary salivary gland.

The spinal origin of the sympathetic vasoconstrictor and secretory fibres to the submaxillary gland of the rat was identified in the pithed rat preparation by means of selective stimulation of small segments of the spinal outflow. Secretory and vascular responses were similar following stimulation in pithed rats to those following stimulation of the isolated superior cervical nerve trunk in anaesthetized rats. The spinal origin of the secretory and vascular fibres was coincident and it is concluded that if a separate control of blood flow and secretion by sympathetic fibres does exist that it must occur at the level of C.N.S. but that the nerves share a common pathway to the gland.

Animals↗
PubMed1997

[Regrowth of central respiratory pathways in neural graft. From research tool on the axonal regeneration to a strategy of post-traumatic reparation].

This review focuses on the regrowth of respiratory pathways after nerve grafting within the central nervous system of the adult rat. After a general presentation of the background and of the grafting procedure, we summarize our nerve grafting results of while it is now well established that severed axons of adult central neurons can regenerate within segments of peripheral nerve partially implanted within the brain or spinal cord, the functional properties of the regenerating neurons remain generally unknown. With a view to assessing the extent to which the functional capacities of central neurons can be maintained after axonal regeneration, we have carried out experiments on central respiratory neurons which are a good example of a highly organized neuronal network with characteristic patterns of spontaneous discharge. We have shown that axonal regrowth of central respiratory neurons was successfully induced in blind-ended medullary and spinal autografts implanted respectively within the respiratory centers of the medulla oblongata and within the cervical spinal cord at the level of descending respiratory pathways. The grafts consisted of true "supplementary nerve" in which normal afferent and efferent respiratory pathways were confirmed by recording respiratory unitary discharges from teased fibers within the grafts. The efferent discharges reflected the activity of central respiratory neurons that had regenerated axons within the grafts: these neurons manifested spontaneous activity and normal responsiveness to respiratory stimuli that resemble those of normal respiratory cells. In order to evaluate the possibility of experimental nerve banking, the feasibility of using short-term and long-term stored nerves as potential spinal nerve grafts was established using in vitro pre-degenerated nerve and cryopreserved nerve grafts after assessment of Schwann cell viability. The extent of respiratory reinnervation of the different grafts (medullary, spinal and stored nerve grafts) was compared. The discussion focuses on the main data and the strategy for future nerve grafting is evoked: functional characteristics of regenerating respiratory axons, extent of graft reinnervation, functional schwann cell survey within stored/grafted nerve and post-traumatic grafting.

Animals↗