Brainstem areas involved in the aspiration reflex: c-Fos study in anesthetized cats

Expression of the immediate-early gene c-fos, a marker of neuronal activation was employed in adult anesthetized non-decerebrate cats, in order to localize the brainstem neuronal populations functionally related to sniff-like (gasp-like) aspiration reflex (AR). Tissues were immunoprocessed using an antibody raised against amino acids of Fos and the avidin-biotin peroxidase complex method. The level of Fos-like immunoreactivity (FLI) was identified and counted in particular brainstem sections under light microscopy using PC software evaluations in control, unstimulated cats and in cats where the AR was elicited by repeated mechanical stimulation of the nasopharyngeal region. Fourteen brainstem regions with FLI labeling, including thirty-seven nuclei were compared for the number of labeled cells. Compared to the control, a significantly enhanced FLI was determined bilaterally in animals with the AR, at various medullary levels. The areas included the nuclei of the solitary tract (especially the dorsal, interstitial and ventrolateral subnuclei), the ventromedial part of the parvocellular tegmental field (FTL -- lateral nuclei of reticular formation), the lateral reticular nucleus, the ambigual and para-ambigual regions, and the retrofacial nucleus. FLI was also observed in the gigantocellular tegmental field (FTG -- medial nuclei of reticular formation), the spinal trigeminal nucleus, in the medullar raphe nuclei (ncl. raphealis magnus and parvus), and in the medial and lateral vestibular nuclei. Within the pons, a significant FLI was observed bilaterally in the parabrachial nucleus (especially in its lateral subnucleus), the Kolliker-Fuse nucleus, the nucleus coeruleus, within the medial region of brachium conjunctivum, in the ventrolateral part of the pontine FTG and the FTL. Within the mesencephalon a significantly enhanced FLI was found at the central tegmental field (area ventralis tegmenti Tsai), bilaterally. Positive FLI found in columns extending from the caudal medulla oblongata, through the pons up to the mid-mesencephalon suggests that the aspiration reflex is thus co-ordinated by a long loop of medullary-pontine-mesencephalic control circuit rather than by a unique "center".     

Vestibular efferent neurons forming projections to the saccule in the guinea pig

A comparative analysis was made of the distribution of vestibular efferent neurons projecting to the saccule and efferent cells sending out axons to the auditory nerve ("cochlear efferent neurons") in the guinea pig, using retrograde horseradish peroxidase axonal transport techniques. Saccular efferent neurons were discovered bilaterally in the subependymal granular layer at the base of the fourth cerebral ventricle and laterally to the facial nerve genu ispsilaterally in the parvocellular reticular nucleus, as well as nuclei of the superior olivary complex: the lateral olivary nucleus and lateral nucleus of the trapezoid body. Cochlear efferent neurons are located ipsilaterally in the pontine reticular caudal nucleus, in the anteroventral cochlear nucleus, and in the lateral and medial olivary nuclei. Neurons were found contralaterally in the medial nucleus of the trapezoid body. It thus emerged that location zones of vestibular saccular efferent neurons and those of cochlear efferent units partially overlapped. The possible involvement of saccular vestibular efferent neurons in the mechanisms of auditory perception is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 22, No. 5, pp. 657–665, September–October, 1990.     

Sources of thalamic afferents projecting to the suprasylvian gyrus of the black sea porpoise

Neurons sending fibers to different loci of the suprasylvian gyrus (SSG) of the porpoise(Phocaena phocaena) cortex were located in the thalamus by retrograde horseradish peroxidase transport and fluorescent tracing techniques. Horseradish peroxidase injection into the anterior section of the suprasylvian gyrus led to retrograde labelling of neurons in the lateral portion of the ventrobasal complex of nuclei and the ventroposteroinferior nucleus. A group of labelled cells was found in the ventral section of the main medial geniculate nucleus. Injecting bisbenzimide into different loci of the medial suprasylvian gyrus also led to retrograde labelling of neurons belonging to the ventral division of the main medial geniculate nucleus. Somewhat lower numbers of labelled cells were found in the inferior nucleus of the pulvinar. Small groups of labelled neurons were also found in the lateral nucleus of the pulvinar, the medioventral nucleus of the medial geniculate body, and the posterior complex of nuclei. A similar distribution of labelled cells was also observed after injecting bisbenzimide into the more caudal portion of the gyrus, although the location of labelled cells in the ventral division of the main medial geniculate nucleus and the lower pulvinar nucleus were shifted in a lateral direction.A. N. Severtsov Institute of Animal Evolutionary Moprhology and Ecology, Academy of Sciences of the USSR, Moscow. National University, Singapore. Translated from Neirofiziologiya, Vol. 21, No. 4, pp. 529–539, July–August, 1989.     

Distribution of reticulospinal neurons in the chicken by retrograde transport of WGA-HRP

To determine the distribution of reticulospinal (RS) neurons in the chicken, WGA-HRP was injected into the cervical or lumbosacral enlargement either unilaterally or bilaterally. The brainstem reticular nuclei sent largely descending fibers to both the spinal enlargements. The mesencephalon (medial and lateral mesencephalic reticular formation) and the rostral pons (nucleus reticularis [n.r.] pontis oralis) project mainly to the cervical enlargement. RS neurons were mainly distributed from the pontomedullary junction to the rostral medulla including n. r. pontis caudalis and pars gigantocellularis, n. r. gigantocellularis, n. r. parvocellularis, n. r. paragigantocellularis, and n. r. subtrigeminalis. It is suggested that the majority of these neurons send axons at least as far as the lumbosacral enlargement. In the lower medulla, RS neurons were distributed in the dorsal and ventral parts of the central nucleus of the medulla.     

Inputs to the torus semicircularis in the electric fish Eigenmannia virescens

Summary The posterior lateral-line lobe, contrary to present belief, projects bilaterally to the torus semicircularis, although the contralateral projection is considerably more extensive. The torus also receives bilateral inputs from the medial octavo-lateralis nuclear complex, the reticular formation, a sublemniscal nucleus, and the nucleus prae-eminentialis. Unilateral inputs to the torus were found originating from the ipsilateral mesencephalic tectum and the contralateral lobus caudalis of the cerebellum. Extensive commissural systems between the right and left torus are also described for the first time.     

The vestibular nuclei in the domestic hen (Gallus domesticus). VII.--Afferents from the spinal cord

Lesions of different parts of the spinal cord at different levels in the hen have been made and the resulting degeneration in the vestibular complex has been studied in silver impregnated sections. Spinovestibular fibres originate from cervical as well as lumbosacral levels of the cord and run in the dorsal part of the lateral funiculus. The spinovestibular fibres from all levels of the spinal cord terminate ipsilaterally in the nucleus Deiters ventralis, the nucleus Deiters dorsalis, the medial nucleus and rostrally in the descending nucleus. The spinovestibular fibres terminating in the above nuclei are few in number while spinovestibular fibres terminating bilaterally in the caudal part of the descending nucleus are much more abundant. In a few cases HRP injections in the vestibular complex resulted in labelled cells in upper cervical segments of the spinal cord localized in lamina VII. The findings are discussed in the light of data concerning the spinovestibular pathway in mammals.     

Does the reticular thalamic nucleus project to the midbrain?

In this study, we investigated whether the reticular thalamic nucleus has a projection to major centres of the midbrain in rats, rabbits and cats. Various tracers (biotinylated dextran, cholera toxin B subunit, fluorescent latex beads) were injected either into the midbrain tectum (deep layers of the superior colliculus) or tegmentum (midbrain reticular and pedunculopontine nuclei). In other experiments, different coloured latex beads (red and green) were injected into the deep layers of the superior colliculus and into the midbrain reticular nucleus of the same animal (rabbits). Our major finding is that in rats, rabbits and cats, there are no retrogradely labelled cells in the reticular thalamic nucleus after tracer injections into the abovementioned midbrain centres. In rabbits and cats, however, there are retrogradely labelled cells lying close to the ventromedial edge of the reticular thalamic nucleus after such injections. We show, by means of immunocytochemical double-labelling, that these retrogradely labelled cells do not lie in the reticular thalamic nucleus as suggested by previous studies, but in the inner small-celled region, a group of small cells that forms part of the zona incerta. Although there appears to be no clear topography of projection of the inner small-celled region, our tracer double-labelling experiments show that separate cells in the inner small-celled region project to individual centres of the midbrain (i.e., there are very few double-labelled cells after double injections). In rats, unlike in rabbits and cats, there is no clearly defined inner small-celled region and there are no retrogradely labelled cells seen along the ventromedial edge of the reticular thalamic nucleus. Our results suggest that in rats, rabbits and cats, there is no projection of the reticular thalamic nucleus to major centres of the midbrain, suggesting that the nucleus may not have a very strong influence on midbrain function, as it does on dorsal thalamic function.     

CCK—8、M—ENK免疫反应结构在猫延髓吻侧腹侧区的分布

用免疫组化 ABC 技术,观察了八肽缩胆囊素(CCK—8),甲硫氨酸脑啡肽(M—ENK)免疫反应(IR)结构在猫延髓吻侧腹侧区的分布。结果表明:CCK—8—IR 细胞分内、外两群:内侧群细胞分布于巨细胞网状核(NGc)、旁巨细胞外侧核(PGL)以及下橄榄核背外侧的网状结构,从吻侧向尾侧逐渐减少;外侧群细胞分布于外侧网状核(LRN)及其背内侧网状结构,从吻侧向尾侧逐渐增多。在中缝苍白核(Rpa)、中缝大核(Rm)仅见少量 CCK—8—IR 细胞。察见 CCK—8—IR纤维主要有3种:粗、细和终末前纤维。CCK—8—IR 纤维在面后核、疑核以及二核紧邻的网状结构最为密集;在 PGL 密度中等;在 NGc、LRN、Rpa 和 Rm 稀疏分布。M—ENK—IR 细胞和纤维分布于 Rpa、Rm、NGc、PGL 和 LRN,此外在面后核、疑核以及二核紧邻的网状结构可见较密集的纤维。     

Central connections of the olfactory bulb in the goldfish,Carassius auratus

Summary The central connections of the goldfish olfactory bulb were studied with the use of horseradish peroxidase methods. The olfactory bulb projects bilaterally to ventral and dorsolateral areas of the telencephalon; further targets include the nucleus praeopticus periventricularis and a caudal olfactory nucleus near the nucleus posterior tuberis in the diencephalon, bilaterally. The contralateral bulb and the anterior commissure also receive an input from the olfactory bulb. Contralateral projections cross in rostral and caudal portions of the anterior commissure and in the habenular commissure. Retrogradely labeled neurons are found in the contralateral bulb and in three nuclei in the telencephalon bilaterally; the neurons projecting to the olfactory bulb are far more numerous on the ipsilateral side than in the contralateral hemisphere. Afferents to the olfactory bulb are found to run almost entirely through the lateral part of the medial olfactory tract, while the bulb efferents are mediated by the medial part of the medial olfactory tract and the lateral olfactory tract. Selective tracing of olfactory sub-tracts reveals different pathways and targets of the three major tract components. Reciprocal connections between olfactory bulb and posterior terminal field suggest a laminated structure in the dorsolateral telencephalon.     

Efferent connections of the striatum with the Ep field of the temporal cortex in the cat

When horseradish peroxidase was injected into the Ep area of the temporal cortex of 5 cats, the distribution of the labelled neurons in the strio-pallidum and in the nucleus of Meynert was similar in all the cases. In the striatum predominantly large cells (in the nucleus caudatus and in the putamen), as well as middle and small (in the putamen) cells were labelled. Comparing the form and size of the labelled cells in the striatum, revealed in Golgi preparations, it is possible to conclude that large labelled neurons correspond to long-axonal sparsely-branching reticular neurons, and middle and small--to long-axonal densely-branching dendroid "spinular" neurons. The large cells of the striatum can be considered as a part of a vast macrocellular ascending system of the forebrain, its preservation maintains the higher integrative functions of the brain.     

c-Fos expression in the central nervous system elicited by phrenic nerve stimulation.

Phrenic nerve afferents (PNa) have been shown to activate neurons in the spinal cord, brain stem, and forebrain regions. The c-Fos technique has been widely used as a method to identify neuronal regions activated by afferent stimulation. This technique was used to identify central neural areas activated by PNa. The right phrenic nerve of urethane-anesthetized rats was stimulated in the thorax. The spinal cord and brain were sectioned and stained for c-Fos expression. Labeled neurons were found in the dorsal horn laminae I and II of the C3-C5 spinal cord ipsilateral to the site of PNa stimulation. c-Fos-labeled neurons were found bilaterally in the medial subnuclei of the nucleus of the solitary tract, rostral ventral respiratory group, and ventrolateral medullary reticular formation. c-Fos-labeled neurons were found bilaterally in the paraventricular and supraoptic hypothalamic nuclei, in the paraventricular thalamic nucleus, and in the central nucleus of the amygdala. The presence of c-Fos suggests that these neurons are involved in PNa information processing and a component of the central mechanisms regulating respiratory function.     

Reciprocal connections between the red nucleus and the trigeminal nuclei: a retrograde and anterograde tracing study.

An anterograde biocytin and a retrograde WGA-colloidal gold study in the rat can provide information about reciprocal communication pathways between the red nucleus and the trigeminal sensory complex. No terminals were found within the trigeminal motor nucleus, in contrast with the facial motor nucleus. A dense terminal field was observed in the parvicellular reticular formation ventrally to the trigeminal motor nucleus. The parvicellular area may be important for the control of jaw movements by rubrotrigeminal inputs. On the other hand, the contralateral rostral parvicellular part of the red nucleus receives terminals from the same zone in the rostral part of the trigeminal sensory complex, where retrogradely labelled neurones were found after tracer injections into the red nucleus. Such relationships could be part of a control loop for somatosensory information from the orofacial area.     

Ascending and descending projections to the inferior colliculus in the rat

The ascending and descending projections to the central nucleus of the inferior colliculus (IC) were studied with the aid of retrograde transport of horseradish peroxidase (HRP). HRP-labelled cells were found in contralateral cochlear nuclei, where the majority of different cell types was stained. Few labelled cells were observed in the ipsilateral cochlear nuclei. HRP-positive neurones were found in all nuclei of the superior olivary complex on the ipsilateral side with the exception of the medial nucleus of the trapezoid body, which was never labelled either ipsilaterally or contralaterally. The largest concentration of HRP-labelled cells was usually observed in the ipsilateral superior olivary nucleus. Smaller numbers of labelled cells were present in contralateral nuclei of the superior olivary complex. Massive projections to the inferior colliculus were found from the contralateral and ipsilateral dorsal nucleus of the lateral lemniscus and ipsilateral ventral nucleus of the lateral lemniscus. Many neurones of the central and external nuclei of the contralateral inferior colliculus were labelled with HRP. Topographic organisation of the pathways ascending to the colliculus was expressed in the cochlear nuclei, lateral superior olivary nucleus and in the dorsal nucleus of the lateral lemniscus. HRP--positive cells were found in layer V of the ipsilateral auditory cortex, however, the evidence for topographic organisation was lacking.     

Nociceptive afferents to the premotor neurons that send axons simultaneously to the facial and hypoglossal motoneurons by means of axon collaterals

It is well known that the brainstem premotor neurons of the facial nucleus and hypoglossal nucleus coordinate orofacial nociceptive reflex (ONR) responses. However, whether the brainstem PNs receive the nociceptive projection directly from the caudal spinal trigeminal nucleus is still kept unclear. Our present study focuses on the distribution of premotor neurons in the ONR pathways of rats and the collateral projection of the premotor neurons which are involved in the brainstem local pathways of the orofacial nociceptive reflexes of rat. Retrograde tracer Fluoro-gold (FG) or FG/tetramethylrhodamine-dextran amine (TMR-DA) were injected into the VII or/and XII, and anterograde tracer biotinylated dextran amine (BDA) was injected into the caudal spinal trigeminal nucleus (Vc). The tracing studies indicated that FG-labeled neurons receiving BDA-labeled fibers from the Vc were mainly distributed bilaterally in the parvicellular reticular formation (PCRt), dorsal and ventral medullary reticular formation (MdD, MdV), supratrigeminal nucleus (Vsup) and parabrachial nucleus (PBN) with an ipsilateral dominance. Some FG/TMR-DA double-labeled premotor neurons, which were observed bilaterally in the PCRt, MdD, dorsal part of the MdV, peri-motor nucleus regions, contacted with BDA-labeled axonal terminals and expressed c-fos protein-like immunoreactivity which induced by subcutaneous injection of formalin into the lip. After retrograde tracer wheat germ agglutinated horseradish peroxidase (WGA-HRP) was injected into VII or XII and BDA into Vc, electron microscopic study revealed that some BDA-labeled axonal terminals made mainly asymmetric synapses on the dendritic and somatic profiles of WGA-HRP-labeled premotor neurons. These data indicate that some premotor neurons could integrate the orofacial nociceptive input from the Vc and transfer these signals simultaneously to different brainstem motonuclei by axonal collaterals.     

Separate populations of neurons in the oculomotor nucleus project to the cerebellum and the abducent nucleus. A retrograde fluorescent double-labelling study in the cat

Retrograde transport of fluorescent substances was used in order to investigate possible branching of axons from neurons in the oculomotor nucleus in the cat. Rhodamine-B-isothiocyanate (RITC) was injected into the cerebellar hemisphere, while Fluoro-Gold was implanted into the abducent nucleus. Neurons single-labelled with either of the dyes were found in the oculomotor nucleus in all cases, but no double-labelled neurons were found. The labelled cells were smaller than motoneurons and located in partly overlapping areas along the dorsal border of the oculomotor nucleus, with the RITC labelled cerebellar projecting cells concentrated medially and the Fluoro-Gold labelled neurons projecting to the abducent nucleus concentrated laterally. The RITC labelled cells were found throughout the rostrocaudal extent of the nucleus, while the Fluoro-Gold labelled cells were mainly found caudally. The present findings demonstrate that oculomotor neurons projecting to the feline cerebellum and abducent nucleus represent separate cell populations.     

Structural Types of Spinal Cord Marginal (Lamina I) Neurons Projecting to the Nucleus of the Tractus Solitarius in the Rat

The structural types of spinal cord marginal (lamina I) neurons projecting to the nucleus of the tractus solitarius (NTS) were studied. Upon injections of cholera toxin subunit B (CTb) into the caudal part of the NTS, including its lateral and medial portions, labeled cells occurred bilaterally in laminae I, IV-VII, and X, and the lateral spinal nucleus (LSN). After injections into the lateral portion alone, only a few cells were labeled in laminae V, VII, and X, and the LSN, and none in the superficial dorsal horn. Of 1882 labeled marginal cells, 38% belonged to the flattened type, 37% to the pyramidal type, and 25% to the fusiform type. Flattened and pyramidal cells were labeled in considerably greater numbers than those reported when other supraspinal targets of these cells were injected with CTb. Since cells in the NTS are known to be under marked 7-aminobutyric acidergic (GABA-ergic) inhibition, it is possible that only strong input conveyed by great numbers of flattened and pyramidal cells is capable of overcoming that barrier. Fusiform cells were labeled in numbers similar to those observed previously after tracer injections into the two other targets of this neuronal type, the parabrachial nuclei and the lateral reticular nucleus. Considering that these regions, as well as the NTS, control cardiovascular and respiratory functions, it is suggested that fusiform cells transmit noxious input that will influence autonomic reflexes processed in the three nuclei.     

Cerebellar afferents in the frogs,Rana esculenta and Rana temporaria

Summary Afferents to the cerebellum in frogs (Rana esculenta, Rana temporaria) were studied by use of retrograde transport of horseradish peroxidase. Following injections restricted to the molecular layer of the cerebellum cell labelling was found in the contralateral inferior olive and the ventral portion of the caudal medullary raphe. Injections involving the granular layer resulted in labelling in the ventral horn of the cervical spinal cord, the caudal spinal trigeminal nucleus, the nucleus caudalis and the medial portion of the nucleus ventralis of the vestibular nerve, the inferior reticular nucleus and the nucleus of the fasciculus longitudinalis medialis. Following larger injections, which may have spread significantly into the cerebellar, secondary gustatory, trigeminal or vestibular nuclei, labelled cell bodies were also found in the nucleus ruber, nucleus solitarius, the rostral spinal trigeminal nucleus and the rostral rhombencephalic reticular formation. It is unclear whether the fibers from these latter areas innervate the cerebellum of the frog, as they do in mammals, or only reach the underlying areas. This situation emphasizes a limitation of the HRP technique when applied to small structures as is often the case in lower vertebrates.Supported by Grant Gr 276 to U. G.-C. from the Deutsche Forschungsgemeinschaft.     

Projections to the midbrain tectum in Salamandra salamandra L.

Following unilateral iontophoretic application of HRP into the optic tectum of Salamandra salamandra, retrogradely HRP-filled cells were found bilaterally in the pretectum, tegmentum isthmi, the reticular formation, pars medialis, and in the nucleus vestibularis magnocellularis. The area octavo-lateralis projects only to the caudal part of the tectum. Ipsilateral projections were noted from the dorsal gray columns of the cervical spinal cord, the dorsal tegmentum, the thalamus dorsalis pars medialis, thalamus dorsalis, pars anterior (to the rostral one-third of the tectum), the thalamus ventralis (in its entire rostro-caudal extent), and the preoptico-hypothalamic complex. Retrogradely filled cells were identified in deeper layers of the contralateral tectum. There are two telencephalic nuclei projecting ipsilaterally to the tectum via the lateral forebrain: the ventral part of the lateral pallium, and the posterior strioamygdalar complex.     

Connections of brainstem respiratory nuclei studied by the retrograde horseradish peroxidase axon transport method

Intrabulbar connections of respiratory nuclei and the medullary reticular formation and also descending pathways from these structures in the spinal cord were studied by the retrograde horseradish peroxidase axonal transport method in cats. Neurons of the nucleus ambiguus and nucleus retroambigualis (ventral respiratory group) and of the ventrolateral part of the nucleus of the tractus solitarius (dorsal respiratory group) were shown to form direct two-way connections with each other and with the medial region of the medulla. Neurons of the pneumotaxic center send uncrossed axons to the nucleus ambiguus and to the medial medullary reticular formation. Neurons of the contralateral homonymous nucleus and neurons of the nucleus of the tractus solitarius are sources of projections of the locus coeruleus. A well developed system of direct connections was found between neurons of respiratory nuclei of the two halves of the brain. The possible role of these nuclear formations in genesis of the respiratory rhythm and regulation of the respiratory and other motor functions of the reticular formation is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 14, No. 2, pp. 149–157, March–April, 1982.     

A crossed projection from the optic tectum to craniocervical premotor areas in the brainstem reticular formation. An anterograde and retrograde tracing study in the mallard (Anas platyrhynchos L.)

The optic tectum in birds receives visual information from the contralateral retina. This information is passed through to other brain areas via the deep layers of the optic tectum. In the present study the crossed tectobulbar pathway is described in detail. This pathway forms the connection between the optic tectum and the premotor area of craniocervical muscles in the contralateral paramedian reticular formation. It originates predominantly from neurons in the ventromedial part of stratum griseum centrale and to a lesser extent from stratum album centrale. The fibers leave the tectum as a horizontal fiber bundle, and cross the midline through the caudal radix oculomotorius and rostral nucleus oculomotorius. On the contralateral side fibers turn to ventral and descend caudally in the contralateral paramedian reticular formation to the level of the obex. Labeled terminals are found in the ipsilateral medial mesencephalic reticular formation lateral to the radix and motor nucleus of the oculomotor nerve, and in the contralateral paramedian reticular formation, along the descending tract. Neurons in the medial mesencephalic reticular formation in turn project to the paramedian reticular formation. Through the crossed tectobulbar pathway visual information can influence the activity of craniocervical muscles via reticular premotor neurons.