Preserved vagal visceromotor function following destruction of the dorsal motor nucleus

1. The dorsal motor nucleus of the vagus was destroyed in cats and after survival periods greater than 10 days, the response of the heart, bronchioles, oesophagus and duodenum to electrical stimulation of the cervical vagi was investigated. The responses obtained from the vagus ipsilateral to the destroyed dorsal motor nucleus were compared to those obtained from the contralateral vagus and with normal controls. No significant differences were demonstrable.2. The responses obtained from stimulation of the cervical vagus following chronic intracranial rhizotomy of the IXth, Xth and XIth nerves were also examined. Visceromotor responses were abolished in three experiments and atypical responses were obtained in two experiments.3. It is concluded that the dorsal motor nucleus does not supply the vagal fibres which produce contraction of the smooth muscle of the bronchioles, oesophagus and duodenum, and that it is not the source of the cardio-inhibitory fibres4. A simple method of destroying a longitudinal column of neurones is described.     

Neurones situated outside the isthmo-optic nucleus and projecting to the eye in adult birds

The centrifugal projection to the eye has been studied by retrograde horseradish peroxidase (HRP) transport in adult pigeons and chickens. About 1500 large neurones outside the contralateral isthmo-optic nucleus and 20 or so ipsilateral ectopic cells contain HRP 0.5-3.5 days after intravitreal HRP injections. The number of ectopic neurones which project to the contralateral eye is more than 20% of the number of labelled cells within the isthmo-optic nucleus. In contrast to the monopolar isthmo-optic neurones, the ectopic cells are a distinct population of large multipolar cells. Previously it has been suggested that many of these cells degenerate during the development of the chick. This study shows that they persist in the adult avian brain where they can be detected in large numbers by the presence of retrogradely transported HRP, provided that an HRP chromogen reaction of sufficient sensitivity is used. The exact target for their axons is unknown.     

Visualization of tyrosine hydroxylase-immunoreactive neurons in the cat dorsal motor vagal cells after treatment with parachlorophenylalanine

We examined tyrosine hydroxylase-immunoreactive (TH-IR) neuronal structures in the cat dorsal motor nucleus of the vagus (DMV) and its adjacent regions. We identified only a few in the caudal part of the DMV and no TH-IR cells at all in its rostral portion. However, after treatment with parachlorophenylalanine (PCPA), numerous TH-IR perikarya were visualized in the DMV. Comments are made on the central catecholamine regulation and the possible influence of serotonin afferents on this nucleus.     

Neurons of the motor cortex projecting commonly on the caudate nucleus and the lower brain stem in the cat

The cortico-caudate projections due to collateral axons of cortico-spinal and/or cortico-bulbar fibers were explored. In 34 cats, 59 neurons in the motor cortex were extracellularly identified to be antidromically activated by stimulation of the caudate nucleus (Cd). Thirty four neurons responded antidromically only to Cd-stimulation, and they were irresponsive to thalamic stimulation. Contrarily, 25 neurons responded antidromically not only to Cd-stimulation but also to stimulation of the cerebral peduncle and/or the medullary pyramid. 40% of the latter were orthodromically activated by thalamic stimulations. They were considered to be important in coordinating the cerebellum and the basal ganglia system.     

大鼠前庭核向迷走神经背侧复合体的间接投射

目的：研究大鼠前庭核向迷走神经背侧复合体的间接投射,探索前庭信息向脑干呕吐区传递的神经通路。方法：向前庭神经下核和前庭神经内侧核注入顺行追踪剂菜豆凝集素（PHA-L）,向迷走神经背侧复合体注入逆行追踪剂荧光金（FG）,用免疫荧光组织化学方法显示PHA-L顺行标记纤维和终末,在荧光显微镜下观察顺行标记PHA-L的纤维和终末与FG逆行标记的细胞重叠区域。结果：在延髓外侧巨细胞旁核和腹外侧区有顺行纤维和终末与逆行标记细胞的重叠。结论：前庭核团可能经外侧巨细胞旁核和腹外侧区向迷走神经背侧复合体有间接投射,为进一步揭示前庭核团与呕吐相关的内脏反应区之间的功能关系提供了形态学基础。     

Corticofugal axons in the lateral geniculate nucleus of the cat

Summary Injections of horseradish peroxidase (HRP) were made into the optic radiations just above the lateral geniculate nucleus of four cats to trace the anterograde filling of corticofugal axons terminating in the perigeniculate and lateral geniculate nuclei. The different types of axons were classified according to axonal diameter and the morphology of the terminal appendages. Judging from their morphological organization we suggest that the corticofugal axons are, in the main, slowly conducting and that they have a restricted terminal distribution which extends, however, to a multiplicity of levels in both perigeniculate and lateral geniculate nuclei. These morphological characteristics may have physiological implications in determining the role of the corticofugal pathway.     

The role of non-myelinated vagal afferent fibres from the lungs in the genesis of tachypnoea in the rabbit

1. The use of a direct current (d.c.) to produce a differential block of conduction in the cervical vagus nerves of rabbits is described; the myelinated fibres are blocked, while the non-myelinated ;C' fibres conduct normally. The method produces reproducible and reversible results.2. The block is equally effective for low and high frequencies of discharge (1-100 Hz). During recovery or development of the block, lower frequencies of discharge can pass but higher frequencies cannot.3. Block of conduction in myelinated fibres is associated with slower, deeper breathing, confirming previous work with cooling.4. A further slowing and deepening of breathing may occur when a differentially blocked (;non-myelinated') nerve is sectioned, and this is mainly apparent when there are pathological conditions in the lungs.5. The respiratory response to the right atrial injection of phenyl diguanide is mediated by non-myelinated thoracic vagal afferent fibres.6. The tachypnoeic response to lung deflation is not mediated by non-myelinated fibres.7. Head's Paradoxical reflex has been demonstrated during partial recovery of conduction in myelinated fibres when only lower frequencies of afferent discharge can pass the area of block.8. A standard technique for providing a reproducible vagally mediated, tachypnoeic response to pulmonary micro-embolism is described using inert carbon-coated microspheres of 50 mum diameter. This tachypnoeic response was unchanged during a differential block indicating that the response was mediated by non-myelinated ;C' fibres.9. Pathological changes such as haemorrhage, oedema, infarction and collapse were absent after micro-embolism, and there were no systematic changes in lung resistance and compliance. The walls of arterioles and adjacent alveoli are distorted by the emboli and these areas are the probable sites of afferent stimulation.     

Fine structure and neurotransmitter cytochemistry of neurons in the rat ventral cochlear nucleus projecting to the ipsilateral dorsal cochlear nucleus

The neural tracer wheat germ agglutinin conjugated to horse radish peroxidase was injected into the rat dorsal cochlear nucleus and acoustic stria. Some labelled neurons in the ipsilateral ventral cochlear nucleus were found as a result. These neurons were studied at the ultrastructural level, and their axo-somatic synaptic profile and glycine immunoreactivity were determined. Most neurons were glycine negative and classified as type I multipolar neurons. The latter showed a different synaptic profile from that of neurons projecting to the contralateral inferior colliculus or cochlear nucleus. This suggests the presence of differing populations of multipolar cells based on their synaptic profile. Few labelled multipolar neurons of type II were found, which appeared glycine negative and, rarely, glycine positive. The latter show an ultrastructure and axo-somatic profile similar to that of glycinergic commissural neurons in the dorsal and ventral cochlear nucleus. In particular, about one-third of boutons contained round synaptic vesicles, which are believed to contain an excitatory neurotransmitter. The ultrastructural analysis of the synaptic boutons in the cochlear nucleus confirms the presence of numerous cases of colocalization of glycine and GABA where flat and pleomorphic synaptic vesicles are mixed. The present study is in accordance with previous tract-tracing light microscopic studies which have indicated that large glycinergic neurons in the ventral cochlear nucleus act as broad-band inhibitory neurons in microcircuits of the dorsal cochlear nucleus and contralateral cochlear nucleus.     

Bulbar neurones with axonal projections to the trigeminal motor nucleus in the cat

Summary The location of bulbar neurones with axons projecting to the ipsi- and contralateral trigeminal motor nucleus were investigated in cats anaesthetized with sodium pentobarbital. Wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) was injected in amounts of 5–24 nl. A volume-calibrated microelectrode was used for recording of evoked potentials and pressure injection of WGA-HRP. The injection site was guided by the position where a maximal antidromic response was evoked by electrical stimulation of the masseteric nerve. The survival time was 19–22 h. In preparations with the depot located in the masseteric subnucleus retrogradely stained neurones were found bilaterally in the borderzone of the trigeminal motor nucleus. Dense populations of stained neurones were observed ipsi- and contralaterally in the dorsal division of the main sensory trigeminal nucleus and the subnucleus- of the oral nucleus of the spinal trigeminal tract. Clusters of WGA-HRP-neurones were observed bilaterally in the lateral tegmental field at the level of the subnucleus- of the oral nucleus of the spinal trigeminal tract, bilaterally dorsal to the facial nucleus and contralaterally adjacent to the hypoglossal nucleus. No stained neurones were found in the gigantocellular reticular nucleus. A group of stained neurones was located in the marginal nucleus of brachium conjunctivum and some were found in the raphé nuclei near obex. Cell profiles were of two types: medium-sized neurones with a triangular profile and 30–40 m diameter, and fusiform neurones 10×50–70 m. Convergence of descending cortical and trigeminal afferent inputs on interneurones located in the lateral borderzone of the trigeminal motor nucleus, i.e. the intertrigeminal area, is reported in the preceding paper.List of Abbreviations BCM Marginal nucleus of the brachium conjunctivum - CAE Nucleus caeruleus - CI Inferior central nucleus - Cu Cuneate nucleus - Cux External cuneate nucleus - DMV Dorsal motor nucleus of the vagus - FTG Gigantocellular tegmental field - FTL Lateral tegmental field - FTP Paralemniscal tegmental field - Gr Gracile nucleus - Mb Medial borderzone of NVmt - NintV Intertrigeminal area - NsV Supratrigeminal nucleus (area) - NVmes Mesencephalic trigeminal nucleus - NVmt Trigeminal motor nucleus - NVsnpr Main sensory trigeminal nucleus - NVsnpr-d Main sensory trigeminal nucleus, dorsal division - NVsnpr-v Main sensory trigeminal nucleus, ventral division - NVspc Caudal nucleus of the spinal trigeminal tract - NVspo- Subnucleus- of the oral nucleus of the spinal trigeminal tract - NVspo- Subnucleus- of the oral nucleus of the spinal trigeminal tract - NVspo- Subnucleus- of the oral nucleus of the spinal trigeminal tract - V Spinal trigeminal tract - NVII Facial nucleus - VII Facial nerve - NXII Hypoglossal nucleus - XII Hypoglossal nerve - Ols Superior olive - Rb Rostral borderzone of NVmt - Vb Ventral borderzone of NVmt - VIN Inferior vestibular nucleus - VSL Superior vestibular nucleus, lateral division     

Non-motoneurons in the facial and motor trigeminal nuclei projecting to the cerebellar flocculus in the cat

Summary The cerebellar projection from the facial and motor trigeminal nuclei was studied in the cat by means of retrograde axonal transport of wheat germ agglutinin-horseradish peroxidase and fluorescent tracers. The feline facial nucleus was cytoarchitectonically subdivided into ventromedial, ventrolateral, lateral, dorsal, intermediate and medial divisions (see Papez 1927), and the motor trigeminal nucleus into medial, ventral, intermediate, lateral and dorsal divisions. The neurons in the facial and motor trigeminal nuclei were classified as small (ovoid to round cells with a maximum diameter of the cell body of about 20 m) or large (polygonal to round cells with maximum diameter of about 40 m). After floccular injections of the wheat germ agglutininhorseradish peroxidase complex, retrogradely labelled cells were found throughout the facial nucleus, but especially in its medial and dorsal divisions. In the motor trigeminal nucleus, labelled neurons were found only in the ventral, intermediate and lateral divisions. Cases with tracer deposition (implants or injections) in other parts of the cerebellar cortex or nuclei were all negative. All facial and motor trigeminal neurons labelled after floccular injections were smaller than the neurons labelled after injections in the facial mimic and masticatory muscles, and only single-labelled neurons were found following floccular injections of Fluoro-Gold and muscular injections of rhodamine-B-isothiocyanate in the same animals. These observations strongly suggest that the neurons in the facial and motor trigeminal nuclei which project to flocculus are of the non-motoneuron type.     

Identification of brainstem interneurons projecting to the trigeminal motor nucleus and adjacent structures in the rabbit

Neurons of several nuclei within the medial pontomedullar reticular formation are active during mastication, but their relationship with other elements of the pattern generating circuits have never been clearly defined. In this paper, we have studied the connection of this area with the trigeminal motor nucleus and with pools of last-order interneurons of the lateral brainstem. Retrograde tracing techniques were used in combination with immunohistochemistry to define populations of glutamatergic and GABAergic neurons. Injections of tracer into the Vth motor nucleus marked neurons in several trigeminal nuclei including the ipsilateral mesencephalic nucleus, the contralateral Vth motor nucleus, the dorsal cap of the main sensory nucleus and the rostral divisions of the spinal nucleus bilaterally. Many last-order interneurons formed a bilateral lateral band running caudally from Regio h (the zone surrounding the Vth motor nucleus), through the parvocellular reticular formation and Vth spinal caudal nucleus. Injections of tracer into Regio h, an area rich in last-order interneurons, marked, in addition to the areas listed above, a large number of neurons in the medial reticular formation bilaterally. The major difference between injection sites was that most neurons projecting to the Vth motor nucleus were located laterally, whereas most of those projecting to Regio h were found medially. Both populations contained glutamatergic and GABAergic neurons intermingled. Our results indicate that neurons of the medial reticular formation that are active during mastication influence Vth motoneurons output via relays in Regio h and other adjacent nuclei.     

Morphological and electrophysiological properties of trigeminal neurones projecting to the accessory abducens nucleus of the cat

Experimental Brain Research - Horseradish peroxidase was injected into the somata or axons of neurones located in the nucleus oralis of the spinal trigeminal complex and projecting to the accessory...